{"id":122726,"date":"2025-09-18T14:17:33","date_gmt":"2025-09-18T12:17:33","guid":{"rendered":"https:\/\/xometry.pro\/?post_type=articles&#038;p=122726"},"modified":"2025-12-01T11:46:17","modified_gmt":"2025-12-01T10:46:17","slug":"geometric-dimensioning-and-tolerancing-gdt","status":"publish","type":"articles","link":"https:\/\/xometry.pro\/en\/articles\/geometric-dimensioning-and-tolerancing-gdt\/","title":{"rendered":"GD&amp;T: Geometric Dimensioning &amp; Tolerancing Explained"},"content":{"rendered":"<div role=\"navigation\" aria-label=\"Table of Contents\" class=\"simpletoc wp-block-simpletoc-toc\"><h2 class=\"simpletoc-title\">Table of Contents<\/h2>\n<ul class=\"simpletoc-list\">\n<li><a href=\"#h-what-is-gd-amp-t-and-why-use-it\">What Is GD&amp;T? And Why Use It?<\/a>\n\n<\/li>\n<li><a href=\"#feature-control-frame\">Feature Control Frame<\/a>\n\n<\/li>\n<li><a href=\"#datums\">Datums<\/a>\n\n<\/li>\n<li><a href=\"#gdampt-categories\">GD&amp;T Categories<\/a>\n\n<\/li>\n<li><a href=\"#flatness-form\">Flatness (Form)<\/a>\n\n<\/li>\n<li><a href=\"#straightness-form\">Straightness (Form)<\/a>\n\n<\/li>\n<li><a href=\"#cylindricity-form\">Cylindricity (Form)<\/a>\n\n<\/li>\n<li><a href=\"#circularity-form\">Circularity (Form)<\/a>\n\n<\/li>\n<li><a href=\"#parallelism-orientation\">Parallelism (Orientation)<\/a>\n\n<\/li>\n<li><a href=\"#perpendicularity-orientation\">Perpendicularity (Orientation)<\/a>\n\n<\/li>\n<li><a href=\"#angularity-orientation\">Angularity (Orientation)<\/a>\n\n<\/li>\n<li><a href=\"#position-location\">Position (Location)<\/a>\n\n<\/li>\n<li><a href=\"#concentricity-location\">Concentricity (Location)<\/a>\n\n<\/li>\n<li><a href=\"#symmetry-location\">Symmetry (Location)<\/a>\n\n<\/li>\n<li><a href=\"#profile-of-a-surface-profile\">Profile of a Surface (Profile)<\/a>\n\n<\/li>\n<li><a href=\"#profile-of-a-line-profile\">Profile of a Line (Profile)<\/a>\n\n<\/li>\n<li><a href=\"#circular-runout-runout\">Circular Runout (Runout)<\/a>\n\n<\/li>\n<li><a href=\"#total-runout-runout\">Total Runout (Runout)<\/a>\n\n<\/li>\n<li><a href=\"#modifiers\">Modifiers<\/a>\n\n\n<\/li>\n\n<\/li>\n\n<li><a href=\"#gdampt-tolerancing-guidelines\">GD&amp;T Tolerancing Guidelines<\/a>\n<\/li><\/ul><\/div>\n\n\n<p>Depending on the manufacturing process, machinery, operator skill, and other factors, parts will always deviate from nominal dimensions. Problems often appear at assembly: features don\u2019t fit or function as intended, or they do, but with extra friction or slack that can significantly reduce part life.<\/p>\n\n\n\n<p>Thus, engineers turn to tolerancing. Dimensional tolerances are the most common way to limit inaccuracies. Most <a href=\"https:\/\/xometry.pro\/en\/articles\/prepare-technical-drawing\/\">engineering drawings<\/a> state a general tolerance class that applies to all dimensions unless otherwise specified.<\/p>\n\n\n\n<p>However, dimensional tolerances alone don\u2019t reflect the intended function of the part, leaving many critical feature behaviors unspecified.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"h-what-is-gd-amp-t-and-why-use-it\"><strong>What Is GD&amp;T? And Why Use It?<\/strong><\/h2>\n\n\n<p><strong>Geometric Dimensioning &amp; Tolerancing (GD&amp;T)<\/strong> provides a complete language to ensure functionality by defining both feature size and geometry.<\/p>\n\n\n\n<p>GD&amp;T is a standardized way to communicate not just size, but also <strong>shape, location, and alignment<\/strong> so a part works exactly as intended. It lets engineers convey design intent to manufacturing and inspection teams for a uniform understanding that maximizes the probability of project success.<\/p>\n\n\n\n<p><strong>Key benefits:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Clear communication<\/strong> &#8211; Symbols make it obvious which features matter for function, removing guesswork between design, machining, and inspection.<br><\/li>\n\n\n\n<li><strong>Controls what matters<\/strong> &#8211; Unlike basic dimensions, GD&amp;T covers size, location, orientation, and form.<br><\/li>\n\n\n\n<li><strong>Interchangeability<\/strong> &#8211; Parts from different batches or suppliers still assemble and function properly.<br><\/li>\n\n\n\n<li><strong>Cost savings<\/strong> &#8211; Tighten tolerances only where needed, reducing scrap and avoiding delays from unfit deliveries.<br><\/li>\n\n\n\n<li><strong>Consistent inspection<\/strong> &#8211; Defines exactly how to measure, reducing disputes and preventing bad parts from slipping through.<br><\/li>\n\n\n\n<li><strong>Flexibility when possible<\/strong> &#8211; Material condition modifiers like <strong>MMC\/LMC<\/strong> can provide bonus tolerance when part size allows.<\/li>\n<\/ul>\n\n\n\n<p>In short, GD&amp;T makes drawings more functional, reduces misunderstandings, and can save both time and money\u2014when you apply it only where it\u2019s truly needed.<\/p>\n\n\n<div class=\"custom-table-block \" id=\"table-id-144\" >\r\n\t<div class=\"search-input-wrapper\">\r\n\t\t<svg width=\"16\" height=\"16\" viewBox=\"0 0 16 16\" fill=\"none\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\">\r\n\t\t\t<path d=\"M15.7812 13.833L12.6659 10.7177C12.5252 10.5771 12.3346 10.499 12.1347 10.499H11.6253C12.4877 9.39596 13.0002 8.00859 13.0002 6.49937C13.0002 2.90909 10.0911 0 6.50083 0C2.91056 0 0.00146484 2.90909 0.00146484 6.49937C0.00146484 10.0896 2.91056 12.9987 6.50083 12.9987C8.01006 12.9987 9.39742 12.4863 10.5004 11.6239V12.1332C10.5004 12.3332 10.5786 12.5238 10.7192 12.6644L13.8345 15.7797C14.1282 16.0734 14.6032 16.0734 14.8938 15.7797L15.778 14.8954C16.0718 14.6017 16.0718 14.1267 15.7812 13.833ZM6.50083 10.499C4.29167 10.499 2.50122 8.71165 2.50122 6.49937C2.50122 4.29021 4.28855 2.49976 6.50083 2.49976C8.70999 2.49976 10.5004 4.28708 10.5004 6.49937C10.5004 8.70852 8.71311 10.499 6.50083 10.499Z\" fill=\"#476175\"\/>\r\n\t\t<\/svg>\r\n\t\t<input type=\"search\" class=\"table-search-input\" id=\"table-search-144\" placeholder=\"Table search\">\r\n\t<\/div>\t\r\n\t<div class=\"table-wrapper\">\r\n\t\t<table style=\"width: 100%;\">\n<tbody>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Name<\/b><\/td>\n<td style=\"width: 22.3979%;\"><b>Description<\/b><\/td>\n<td style=\"width: 32.6746%;\"><b>When to Use<\/b><\/td>\n<td style=\"width: 21.2121%;\"><b>Drawing Examples\u00a0<\/b><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Flatness<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">All surface points must fall between two parallel planes. <\/span><i><span style=\"font-weight: 400;\">(No datum.)<\/span><\/i><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Mating\/sealing faces need even contact; fixtures need stable seating.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Base plate surface lies flush on the granite table without rocking.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Straightness\u00a0<\/b><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Axis deviation limited inside a small cylindrical zone. <\/span><i><span style=\"font-weight: 400;\">(Feature of size.)<\/span><\/i><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Guide shafts\/spindles need true axes for smooth motion and low wear.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Long shaft runs within straightness limits\u2014no mid-span bow.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Cylindricity<\/b><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Entire cylindrical surface must fit a single coaxial tolerance cylinder.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Rotating\/press-fit cylinders must run true along their length.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Bearing journal conforms to one coaxial cylinder along its full length.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Circularity (Roundness)<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Every cross-section must fit between two concentric circles. <\/span><i><span style=\"font-weight: 400;\">(No datum.)<\/span><\/i><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Isolated round sections need uniformity without building a DRF.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Turned shaft section measures uniformly round at every angle.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Parallelism<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Surface\/axis oriented parallel to the datum within a defined zone.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Opposed faces\/axes must track together to avoid tilt or pinch.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Top face of a machined block remains parallel to the bottom datum face.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Perpendicularity<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Surface\/axis oriented 90\u00b0 to the datum within a defined zone.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Bores to seats; square load paths; accurate alignments.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Milled edge is square (90\u00b0) to the datum surface.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Angularity<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Surface\/axis oriented at a specified basic angle (\u226090\u00b0) to a datum.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Non-right-angle features critical to meshing\/flow\/assembly.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Chamfer held at 45\u00b0 relative to the base datum.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Position<\/b><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Locates an axis\/center at true position (cylindrical zone; uses datums).<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Patterns\/pins\/bores must assemble reliably across suppliers.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Flange bolt-hole centers located at their true positions on the pattern.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Concentricity<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Median points align to a datum axis.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Mass-center alignment for balance\u2014usually replace with position\/runout.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Stepped shaft\u2019s small diameter shares the same center as the pilot bore.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Symmetry<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Feature midplane centered on a datum plane.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Keep equal clearance\/load on both sides of a midplane.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Forked slot walls are equally spaced about the center plane.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Profile of a Surface<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Entire surface must lie within a 3D tolerance band.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Freeform\/compound faces must follow CAD for function\/aesthetics.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Car-door outer skin follows CAD surface within the profile band.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Profile of a Line<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Any chosen section must lie within a 2D tolerance band.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Control edge\/section smoothness where visual fit matters.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Bumper opening section matches the specified template curve.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Circular Runout<\/b><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Limits section variation during rotation about a datum axis.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Control face \u201cwobble\u201d at each section to reduce vibration.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Brake disc face shows minimal variation over one revolution.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>Total Runout<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Limits full-surface variation during rotation.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><span style=\"font-weight: 400;\">Full-length journals\/sealing surfaces must run true (NVH, leaks).<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Driveshaft journal tracks true along its entire length while rotating.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>MMC (Maximum Material Condition)<\/b><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Adds <\/span><b>bonus<\/b><span style=\"font-weight: 400;\"> tolerance as the feature departs from max material.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><b>Clearance fits:<\/b><span style=\"font-weight: 400;\"> pins\/holes when assembly ease matters but strength is unaffected.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Locating hole at its smallest size permits bonus position tolerance.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>LMC (Least Material Condition)<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">Adds <\/span><b>bonus<\/b><span style=\"font-weight: 400;\"> tolerance as the feature departs from least material.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><b>Edge distance \/ wall-thickness protection<\/b><span style=\"font-weight: 400;\"> near holes or cutouts.<\/span><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Edge-near hole retains minimum wall by using LMC bonus.<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 22.6614%;\"><b>RFS (Regardless of Feature Size)<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/td>\n<td style=\"width: 22.3979%;\"><span style=\"font-weight: 400;\">No bonus; geometry held regardless of actual size.<\/span><\/td>\n<td style=\"width: 32.6746%;\"><b>Optical mounts, sealing features, precision location despite clearance.<\/b><\/td>\n<td style=\"width: 21.2121%;\"><span style=\"font-weight: 400;\">Alignment bore held at position regardless of actual size.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Overview of the most widely used GD&amp;T symbols with explanations and real-world drawing examples.<\/p>\n\t<\/div>\r\n<\/div>\r\n<style>\r\n\t.custom-table-block table{\r\n\t\theight: initial!important;\r\n\t}\r\n\t.search-input-wrapper{\r\n\t\tposition: relative;\r\n\t\tmargin-bottom: 24px;\r\n\t}\r\n\t.search-input-wrapper svg{\r\n\t\tposition: absolute;\r\n\t\ttop:50%;\r\n\t\tleft:12px;\r\n\t\ttransform: translateY(-50%);\r\n\t}\r\n\t.table-search-input{\r\n\t\tpadding: 0 0 0 40px;\r\n\t\tborder:1px solid #C1CAD1;\r\n\t\theight: 44px;\r\n\t\twidth: 201px;\r\n\t\tcolor:#092C47;\r\n\t\tfont-family: Open Sans;\r\n\t\tfont-size: 16px;\r\n\t\tfont-weight: 400;\r\n\t\tline-height: 24px;\r\n\t\tletter-spacing: 0em;\r\n\t\ttext-align: left;\r\n\t}\r\n\t.table-search-input::placeholder{\r\n\t\tcolor:#092C47;\r\n\t}\r\n\t\r\n\t.custom-table-block thead th{\r\n\t\ttext-align: left;\r\n\t\twhite-space:nowrap;\r\n\t}\r\n\t\r\n\t.custom-table-block thead{\r\n\t\tmargin-bottom: 14px;\r\n\t}\r\n\r\n\t.custom-table-block tbody tr:nth-child(odd){\r\n\t\tbackground-color: #F6F9FF;\r\n\t}\r\n\r\n\t.custom-table-block tbody, .custom-table-block thead, .custom-table-block tr, .custom-table-block td, .custom-table-block th{\r\n\t\theight: initial!important;\r\n\t}\r\n\t\r\n\t.custom-table-block tbody td{\r\n\t\tcolor:#092C47;\r\n\t\tfont-family: Open Sans;\r\n\t\tfont-size: 16px;\r\n\t\tfont-weight: 400;\r\n\t\tline-height: 24px;\r\n\t\tletter-spacing: 0em;\r\n\t\ttext-align: left;\r\n\t\tpadding: 7px;\r\n\t}\r\n\t\r\n\t.custom-table-block thead th{\r\n\t\tfont-family: Open Sans;\r\n\t\tfont-size: 16px;\r\n\t\tfont-weight: 700;\r\n\t\tline-height: 24px;\r\n\t\tletter-spacing: 0em;\r\n\t\ttext-align: left;\r\n\t\tcolor:#092C47;\r\n\t\tposition: relative;\r\n\t}\r\n\t.custom-table-block thead th:after{\r\n\t\tcontent:\"\";\r\n\t\tdisplay: inline-block;\r\n\t\tbackground-image: url(\"data:image\/svg+xml,%3Csvg width='12' height='8' viewBox='0 0 12 8' fill='none' xmlns='http:\/\/www.w3.org\/2000\/svg'%3E%3Cpath d='M10.585 0.585938L6 5.17094L1.415 0.585938L0 2.00094L6 8.00094L12 2.00094L10.585 0.585938Z' fill='%23476175'\/%3E%3C\/svg%3E%0A\");\r\n\t\tmargin-left: 8px;\r\n\t\tbackground-position: center center;\r\n\t\tbackground-size: 12px 7.5px;\r\n\t\tbackground-repeat: no-repeat;\r\n\t\twidth: 24px;\r\n\t\theight: 12px;\r\n\t}\r\n\t.custom-table-block{\r\n\t\tmargin: 20px 0;\t\r\n\t}\r\n\t.custom-table-block .table-wrapper{\r\n\t\twidth: 100%;\r\n\t\toverflow-x: auto;\r\n\t}\r\n\t@media(max-width: 768px){\r\n\t\t\/* .custom-table-block tbody td{\r\n\t\t\twhite-space: nowrap;\r\n\t\t} *\/\r\n\t\t.custom-table-block .table-wrapper{\r\n\t\t\tmax-width: calc(100vw - 16px);\r\n\t\t}\r\n\t}\r\n<\/style>\r\n\n\n<h2 class=\"wp-block-heading\" id=\"feature-control-frame\"><strong>Feature Control Frame<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"976\" height=\"223\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image.png\" alt=\"Feature control frame showing position tolerance with datums B and C.\" class=\"wp-image-122742\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image.png 976w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-300x69.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-768x175.png 768w\" sizes=\"(max-width: 976px) 100vw, 976px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image.png\" data-fancybox=\"gallery-122726\" data-caption=\"Example of a GD&amp;T feature control frame: position tolerance of \u00d80.15 at least material condition, relative to datums B and C.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Example of a GD&amp;T feature control frame: position tolerance of \u00d80.15 at least material condition, relative to datums B and C.<\/em><\/figcaption><\/figure>\n\n\n\n<p>The feature control frame (FCF) carries all information needed by both manufacturing and inspection. It specifies <strong>what<\/strong> geometric control applies, <strong>how much<\/strong> variation is allowed, and <strong>relative to what<\/strong> references.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>The leader arrow<\/strong> &#8211; The arrow indicates what surface or feature is affected by the geometric tolerances. Sometimes there\u2019s no leader: the FCF may be placed next to a <strong>basic<\/strong> or <strong>diametric<\/strong> dimension; in that case, the feature of size is affected.<\/li>\n\n\n\n<li><strong>Geometric tolerance symbol<\/strong> &#8211; The first box of the feature control frame defines which geometric tolerance is used, in this case position.<\/li>\n\n\n\n<li><strong>Feature tolerance<\/strong> -The numeric value is always present (e.g., 0.15 mm). Additional symbols may define the zone shape (e.g., \u2300 for a cylindrical zone). This cell can also include a material condition modifier\u2014MMC (\u24c2) for Maximum Material Condition or LMC (\u24c1) for Least Material Condition.<\/li>\n\n\n\n<li><strong>Datums<\/strong> &#8211; The following compartments list the datum references (e.g., |B|C|) that establish how the tolerance is oriented and located.<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\" id=\"datums\"><strong>Datums<\/strong><\/h2>\n\n\n<p>A <strong>datum<\/strong> is a <em>theoretically exact<\/em> reference, used to measure and verify geometric controls in GD&amp;T. Because real parts and fixtures are never perfect, GD&amp;T distinguishes between <strong>datum features<\/strong>, <strong>datums<\/strong>, and <strong>datum simulators<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Datum feature<\/strong> &#8211; The real surface\/edge\/axis on the part that you designate as a reference (e.g., a machined face, a bore axis). It has imperfections.<br><\/li>\n\n\n\n<li><strong>Datum<\/strong> &#8211; The ideal, perfect reference derived from the datum feature (e.g., a mathematically perfect plane or axis).<br><\/li>\n\n\n\n<li><strong>Datum simulator<\/strong> &#8211; The physical device that <em>acts like<\/em> the datum during inspection or setup (e.g., a surface plate, pins, V-blocks). The datum feature is brought into contact with the simulator to establish the measurement setup.<br><\/li>\n<\/ul>\n\n\n\n<p>This has direct implications for inspection results. Many FCFs reference more than one datum; the <strong>order<\/strong> of datums in the FCF defines how the coordinate system is built\u2014this is the <strong>datum reference frame (DRF)<\/strong> used for measurement.<\/p>\n\n\n\n<p><strong>Building the DRF (A\u2013B\u2013C):<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Primary datum (A)<\/strong> &#8211; Establishes the first reference plane\/axis; requires at least <strong>three<\/strong> points of contact.<br><\/li>\n\n\n\n<li><strong>Secondary datum (B)<\/strong> &#8211; Adds orientation\/location constraint; at least <strong>two<\/strong> points of contact.<br><\/li>\n\n\n\n<li><strong>Tertiary datum (C)<\/strong> &#8211; Final constraint; at least <strong>one<\/strong> point of contact.<br><\/li>\n<\/ul>\n\n\n\n<p>Changing the <strong>A\u2013B\u2013C order<\/strong> changes how the part is constrained on the simulator and can change inspection results. Choose datums\u2014and their sequence\u2014to match <strong>functional assembly<\/strong> and <strong>actual inspection<\/strong> setups.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"gdampt-categories\"><strong>GD&amp;T Categories<\/strong><\/h2>\n\n\n<p>Geometric dimensioning and tolerancing is divided into 5 distinct categories:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Form<\/strong> &#8211; Control the inherent shape\/consistency of features without referencing datums.\n<ul class=\"wp-block-list\">\n<li><strong>Flatness<\/strong><\/li>\n\n\n\n<li><strong>Straightness<\/strong><\/li>\n\n\n\n<li><strong>Cylindricity<\/strong><\/li>\n\n\n\n<li><strong>Circularity<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Orientation &#8211; <\/strong>Control the tilt or alignment of a feature relative to a datum. Require at least one datum as reference.\n<ul class=\"wp-block-list\">\n<li><strong>Parallelism<\/strong><\/li>\n\n\n\n<li><strong>Perpendicularity<\/strong><\/li>\n\n\n\n<li><strong>Angularity<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Location<\/strong> &#8211; Position a feature&#8217;s axis, center plane, or center point precisely by referencing datums. These datums act as a coordinate system, establishing the permissible deviation of a feature from its <strong>true position<\/strong> or <strong>true location<\/strong>. This ideal, intended position is defined by basic dimensions, which are standard linear dimension lines.\n<ul class=\"wp-block-list\">\n<li><strong>Position<\/strong><\/li>\n\n\n\n<li><strong>Concentricity <\/strong>(stripped from ASME)<\/li>\n\n\n\n<li><strong>Symmetry <\/strong>(stripped from ASME)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Profile<\/strong> &#8211; Control 2D\/3D outlines relative to datums for proper alignment.\n<ul class=\"wp-block-list\">\n<li><strong>Profile of a surface <\/strong>(3D)<\/li>\n\n\n\n<li><strong>Profile of a line<\/strong> (2D)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Runout<\/strong> &#8211; Controls surface variation as a part rotates around a datum axis. It is unique in that it checks both geometry and alignment, and is commonly used to prevent vibration in components such as axles and shafts.\n<ul class=\"wp-block-list\">\n<li><strong>Circular runout<\/strong><\/li>\n\n\n\n<li><strong>Total runout<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\" id=\"flatness-form\"><strong>Flatness (Form)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"648\" height=\"274\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-1.png\" alt=\"Flatness tolerance symbol applied to a rectangular feature in a technical drawing.\" class=\"wp-image-122754\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-1.png 648w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-1-300x127.png 300w\" sizes=\"(max-width: 648px) 100vw, 648px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-1.png\" data-fancybox=\"gallery-122726\" data-caption=\"Flatness tolerance of 0.3 mm applied to a surface, ensuring the face lies between two parallel planes.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-1.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Flatness tolerance of 0.3 mm applied to a surface, ensuring the face lies between two parallel planes.<\/em><\/figcaption><\/figure>\n\n\n\n<p>The flatness tolerance defines a zone between two parallel planes. The zone&#8217;s thickness is indicated in the feature control frame. To meet the requirements, all points on the surface must remain within the tolerance zone.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"909\" height=\"284\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-2.png\" alt=\"CAD model showing flatness requirement for a surface resting evenly against a reference plane.\" class=\"wp-image-122766\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-2.png 909w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-2-300x94.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-2-768x240.png 768w\" sizes=\"(max-width: 909px) 100vw, 909px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-2.png\" data-fancybox=\"gallery-122726\" data-caption=\"Flatness ensures even contact between mating parts. In this example, the surface must lie flat to provide uniform contact with the reference plane.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-2.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Flatness ensures even contact between mating parts. In this example, the surface must lie flat to provide uniform contact with the reference plane.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Flatness is often used when a face must mate with another part to ensure <strong>even contact<\/strong>. It can also be applied to <strong>features of size<\/strong> (anything with a measurable size like a cutout). In that case, the two-plane zone is formed <strong>through the middle<\/strong> of the measured feature.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"509\" height=\"426\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-3.png\" alt=\"Flatness tolerance applied to a part with hole feature.\" class=\"wp-image-122778\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-3.png 509w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-3-300x251.png 300w\" sizes=\"(max-width: 509px) 100vw, 509px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-3.png\" data-fancybox=\"gallery-122726\" data-caption=\"Flatness tolerance example showing a surface controlled within 0.2 mm across a cutout feature.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-3.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Flatness tolerance example showing a surface controlled within 0.2 mm across a cutout feature.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Geometric dimensioning and tolerancing (GD&amp;T) is typically applied to parts and features requiring precise, often imperceptible tolerances, particularly in machining. However, flatness tolerance has broader applications. For instance, in large-scale sheet or tube cutting, laser heating can lead to visible bends, making flatness a critical consideration.<\/p>\n\n\n\n<p>So when doing a lot of cutouts on a 120x60x6000 mm rectangular tube, it can end up curved like a banana. Defining the tolerance zone is simple to do and simple to measure, as you just have to lay down the tube and measure its highest point to see whether it fits the tolerance zone or not.<\/p>\n\n\n\n<p><strong>Flatness vs. surface roughness:<\/strong> Flatness addresses overall shape (macro), <a href=\"https:\/\/xometry.pro\/en\/articles\/cnc-machining-surface-roughness\/\">surface roughness<\/a> addresses texture (micro). A surface can be flat but rough, or warped but smooth.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> When two faces will mate and need evenness: a <strong>valve body sealing face<\/strong> to prevent leaks.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"straightness-form\"><strong>Straightness (Form)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"646\" height=\"309\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-4.png\" alt=\"Straightness tolerance applied to a shaft axis.\" class=\"wp-image-122790\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-4.png 646w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-4-300x143.png 300w\" sizes=\"(max-width: 646px) 100vw, 646px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-4.png\" data-fancybox=\"gallery-122726\" data-caption=\"Straightness tolerance example with a 0.2 mm limit applied along the shaft axis for proper alignment.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-4.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Straightness tolerance example with a 0.2 mm limit applied along the shaft axis for proper alignment.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Straightness is the same tolerance as flatness, minus one dimension. Meaning the tolerance zone is 2D instead of 3D.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"845\" height=\"356\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-5.png\" alt=\"Cylinder being measured for straightness tolerance using a reference plane.\" class=\"wp-image-122802\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-5.png 845w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-5-300x126.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-5-768x324.png 768w\" sizes=\"(max-width: 845px) 100vw, 845px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-5.png\" data-fancybox=\"gallery-122726\" data-caption=\"Straightness tolerance applied to a cylindrical surface, measured with a reference plane for even axis alignment.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-5.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Straightness tolerance applied to a cylindrical surface, measured with a reference plane for even axis alignment.<\/em><\/figcaption><\/figure>\n\n\n\n<p>A simple way to think about straightness is through measurement: a <a href=\"https:\/\/www.aberlink.com\/company\/what-is-a-cmm\/\">coordinate measuring machine (CMM)<\/a> moves in a single straight line on a surface, checking if all points on that line fall within the tolerance zone. On a cylindrical part, you can draw many parallel lines to measure. Note: all lines can individually pass while there is still dislocation between lines not checked.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"845\" height=\"285\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-6.png\" alt=\"Technical drawing of a shaft with straightness tolerance applied to its axis.\" class=\"wp-image-122814\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-6.png 845w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-6-300x101.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-6-768x259.png 768w\" sizes=\"(max-width: 845px) 100vw, 845px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-6.png\" data-fancybox=\"gallery-122726\" data-caption=\"Straightness tolerance on a shaft diameter, defining a cylindrical zone around the axis to ensure proper alignment.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-6.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Straightness tolerance on a shaft diameter, defining a cylindrical zone around the axis to ensure proper alignment.<\/em><\/figcaption><\/figure>\n\n\n\n<p>When straightness is applied to a <strong>feature of size<\/strong> (e.g., a shaft diameter), it creates a <strong>cylindrical zone around the axis<\/strong>. The axis (or derived median line) must lie within that zone along the length. The same applies to a <strong>hole axis<\/strong>.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"894\" height=\"436\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-7.png\" alt=\"Hollow cylinder with an internal guide rail showing straightness requirement.\" class=\"wp-image-122826\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-7.png 894w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-7-300x146.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-7-768x375.png 768w\" sizes=\"(max-width: 894px) 100vw, 894px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-7.png\" data-fancybox=\"gallery-122726\" data-caption=\"Hollow cylinder with an internal guide rail showing straightness requirement.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-7.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Hollow cylinder with an internal guide rail showing straightness requirement.<\/em><\/figcaption><\/figure>\n\n\n\n<p><strong>Use example:<\/strong> Where something must be really straight to fit or seal well: a <strong>CNC guide rail <\/strong>for smooth motion.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"cylindricity-form\"><strong>Cylindricity (Form)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"716\" height=\"324\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-8.png\" alt=\"GD&amp;T cylindricity tolerance applied to a shaft\" class=\"wp-image-122838\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-8.png 716w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-8-300x136.png 300w\" sizes=\"(max-width: 716px) 100vw, 716px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-8.png\" data-fancybox=\"gallery-122726\" data-caption=\"Cylindricity controls a cylindrical surface so all points stay within a uniform tolerance zone.\" aria-label=\"Open full image\"><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-8.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Cylindricity controls a cylindrical surface so all points stay within a uniform tolerance zone.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Cylindricity defines a tolerance zone that is <strong>uniformly surrounding a cylinder,<\/strong> pin or hole feature. Every point on the feature surface must fall within the zone.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"940\" height=\"505\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-9.png\" alt=\"Cylindricity example on a shaft surface\" class=\"wp-image-122850\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-9.png 940w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-9-300x161.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-9-768x413.png 768w\" sizes=\"(max-width: 940px) 100vw, 940px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-9.png\" data-fancybox=\"gallery-122726\" data-caption=\"Cylindricity ensures the shaft is both round and straight along its full length, minimizing imbalance.\" aria-label=\"Open full image\"0><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-9.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Cylindricity ensures the shaft is both round and straight along its full length, minimizing imbalance.<\/em><\/figcaption><\/figure>\n\n\n\n<p>In essence, cylindricity is a 2-in-1 control that encompasses circularity (roundness at each cross-section) and straightness (no axis wander) along the entire length.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> A <strong>high-speed motor shaft<\/strong> that must be straight and round along its length to minimize <strong>imbalance<\/strong>.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"circularity-form\"><strong>Circularity (Form)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"901\" height=\"400\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-10.png\" alt=\"GD&amp;T circularity tolerance applied to a shaft cross-section.\" class=\"wp-image-122862\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-10.png 901w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-10-300x133.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-10-768x341.png 768w\" sizes=\"(max-width: 901px) 100vw, 901px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-10.png\" data-fancybox=\"gallery-122726\" data-caption=\"Circularity controls the roundness of each cross-section, keeping points within two concentric circles.\" aria-label=\"Open full image\"1><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-10.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Circularity controls the roundness of each cross-section, keeping points within two concentric circles.<\/em><\/figcaption><\/figure>\n\n\n\n<p><strong>Circularity (roundness)<\/strong> controls the <strong>roundness of a single cross-section<\/strong>. The zone is two <strong>concentric circles<\/strong>; there is <strong>no length<\/strong> component. Circularity is to cylindricity what straightness is to flatness. The tolerance zone&#8217;s width is again determined by the numerical value in the control frame.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"915\" height=\"485\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-11.png\" alt=\"Circularity example on a shaft cross-section\" class=\"wp-image-122874\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-11.png 915w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-11-300x159.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-11-768x407.png 768w\" sizes=\"(max-width: 915px) 100vw, 915px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-11.png\" data-fancybox=\"gallery-122726\" data-caption=\"Circularity example on a shaft cross-section\" aria-label=\"Open full image\"2><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-11.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Circularity example on a shaft cross-section<\/em><\/figcaption><\/figure>\n\n\n\n<p>Because circularity applies <strong>section by section<\/strong>, the part may have different cross-section diameters with no issue; each section has the <strong>same zone width<\/strong> but a different nominal.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> A <strong>bearing seat<\/strong> that must be round for <strong>even load distribution<\/strong>.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"parallelism-orientation\"><strong>Parallelism (Orientation)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"737\" height=\"322\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-12.png\" alt=\"Technical drawing showing a parallelism tolerance applied to a surface with reference to datum A.\" class=\"wp-image-122886\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-12.png 737w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-12-300x131.png 300w\" sizes=\"(max-width: 737px) 100vw, 737px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-12.png\" data-fancybox=\"gallery-122726\" data-caption=\"Example of parallelism tolerance requiring a surface to remain parallel to datum A within 0.15 mm.\" aria-label=\"Open full image\"3><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-12.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Example of parallelism tolerance requiring a surface to remain parallel to datum A within 0.15 mm.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Parallelism states that a surface (or axis) must be <strong>parallel to a datum<\/strong> within a specified tolerance zone. In CAD you pick a reference and get perfection; in GD&amp;T you define a <strong>measurable tolerance zone<\/strong> about that ideal.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> Two surfaces or axes must be parallel for function: the <strong>rails of a linear actuator<\/strong>.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"perpendicularity-orientation\"><strong>Perpendicularity (Orientation)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"545\" height=\"356\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-13.png\" alt=\"Technical drawing showing a perpendicularity tolerance applied to a surface with respect to datum A.\" class=\"wp-image-122898\" style=\"max-width:840px;height:auto\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-13.png 545w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-13-300x196.png 300w\" sizes=\"(max-width: 545px) 100vw, 545px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-13.png\" data-fancybox=\"gallery-122726\" data-caption=\"Example of perpendicularity tolerance ensuring a surface is 90\u00b0 to datum A within 0.2 mm.\" aria-label=\"Open full image\"4><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-13.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Example of perpendicularity tolerance ensuring a surface is 90\u00b0 to datum A within 0.2 mm.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Perpendicularity controls a feature or plane at <strong>90\u00b0<\/strong> to a datum feature. Although the nominal is an angle, the <strong>tolerance is given in linear units<\/strong> (e.g., mm).<\/p>\n\n\n\n<p><strong>Use example:<\/strong> Alignment or load transfer requires near-perfect perpendicularity: a <strong>cutting tool holder bore<\/strong> relative to the holder base to avoid misalignment.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"angularity-orientation\"><strong>Angularity (Orientation)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"633\" height=\"321\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-14.png\" alt=\"Technical drawing showing angularity tolerance applied at 45\u00b0 to datum A. \" class=\"wp-image-122910\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-14.png 633w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-14-300x152.png 300w\" sizes=\"(max-width: 633px) 100vw, 633px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-14.png\" data-fancybox=\"gallery-122726\" data-caption=\"Example of angularity tolerance requiring a surface to maintain a 45\u00b0 angle relative to datum A within 0.2 mm.\" aria-label=\"Open full image\"5><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-14.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Example of angularity tolerance requiring a surface to maintain a 45\u00b0 angle relative to datum A within 0.2 mm.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Similar to perpendicularity, but the angle to the datum is <strong>not 90\u00b0<\/strong>. The nominal angle is defined by a <strong>basic dimension<\/strong> (e.g., 45\u00b0); the angularity tolerance provides <strong>linear<\/strong> room for error. This is often more practical for inspection with CMMs or gauges than a pure angular tolerance.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> A specific angle between planes is required: a <strong>gear tooth face angle<\/strong> for proper meshing and load distribution.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"position-location\"><strong>Position (Location)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"737\" height=\"555\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-15.png\" alt=\"Technical drawing showing positional tolerance applied to a hole feature with datums A and B.\" class=\"wp-image-122922\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-15.png 737w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-15-300x226.png 300w\" sizes=\"(max-width: 737px) 100vw, 737px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-15.png\" data-fancybox=\"gallery-122726\" data-caption=\"Example of position tolerance controlling hole axis location relative to datums A and B within a 0.15 mm cylindrical zone.\" aria-label=\"Open full image\"6><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-15.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Example of position tolerance controlling hole axis location relative to datums A and B within a 0.15 mm cylindrical zone.<\/em><\/figcaption><\/figure>\n\n\n\n<p><strong>Position<\/strong> is one of the most used GD&amp;T controls. Instead of rectangular tolerance \u201cboxes\u201d from linear dimensions, position defines a <strong>cylindrical tolerance zone<\/strong> centered at the <strong>true position<\/strong> (from basic dimensions).This allows you to control not only where a feature (e.g., a hole axis) is, <strong>but also to ensure<\/strong> it is properly oriented to the referenced datums.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"815\" height=\"545\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-16.png\" alt=\"\" class=\"wp-image-122934\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-16.png 815w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-16-300x201.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-16-768x514.png 768w\" sizes=\"(max-width: 815px) 100vw, 815px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-16.png\" data-fancybox=\"gallery-122726\" data-caption=\"\" aria-label=\"Open full image\"7><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-16.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><\/figure>\n\n\n\n<p><em>Basic dimensions (boxed) establish the <\/em><strong><em>true position<\/em><\/strong><em>; the <\/em><strong><em>position<\/em><\/strong><em> control defines the allowed <\/em><strong><em>cylindrical tolerance zone<\/em><\/strong><em> about that true position.<\/em><\/p>\n\n\n\n<p><strong>Use example:<\/strong> Exact hole\/pin locations critical for assembly: a <strong>bolt pattern on a flange<\/strong> for gasket alignment.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"concentricity-location\"><strong>Concentricity (Location)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"891\" height=\"411\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-17.png\" alt=\"Concentricity tolerance applied to a shaft relative to datum A.\" class=\"wp-image-122946\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-17.png 891w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-17-300x138.png 300w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-17-768x354.png 768w\" sizes=\"(max-width: 891px) 100vw, 891px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-17.png\" data-fancybox=\"gallery-122726\" data-caption=\"Concentricity tolerance applied to a shaft relative to datum A.\" aria-label=\"Open full image\"8><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-17.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Concentricity tolerance applied to a shaft relative to datum A.<\/em><\/figcaption><\/figure>\n\n\n\n<p>In the most recent revision of the ASME standard, <a href=\"https:\/\/www.asme.org\/codes-standards\/find-codes-standards\/y14-5-dimensioning-tolerancing\">ASME Y14.5-2018,<\/a> concentricity was removed. This is because its definition can be covered by position tolerance and runout, both of which are more frequently used. However, it is important to note that concentricity is still present in the <a href=\"https:\/\/www.iso.org\/committee\/54924\/x\/catalogue\/\">equivalent family of ISO standards.<\/a><\/p>\n\n\n\n<p>Concentricity requires the median points of all diametrically opposed surface elements to fall within a cylindrical zone coaxial with a datum axis. While it can be justified mechanically, it complicates inspection (CMM data-heavy). Often replaced by position and\/or runout in ASME workflows.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"699\" height=\"343\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-18.png\" alt=\"3D model showing concentricity alignment of two shafts along a common axis.\" class=\"wp-image-122958\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-18.png 699w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-18-300x147.png 300w\" sizes=\"(max-width: 699px) 100vw, 699px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-18.png\" data-fancybox=\"gallery-122726\" data-caption=\"3D model showing concentricity alignment of two shafts along a common axis.\" aria-label=\"Open full image\"9><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-18.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>3D model showing concentricity alignment of two shafts along a common axis.<\/em><\/figcaption><\/figure>\n\n\n\n<p>For a stepped shaft with varying diameters, aiming for optimal rotational smoothness. You can designate the axis of one section (e.g., the thicker one) as the datum axis. Then, conceptualize an imaginary cylindrical tolerance tube extending from this datum axis. The key is that all axis points of the shaft&#8217;s second section must remain confined within this extended tolerance tube.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> When the <strong>mass centerline<\/strong> must align for balance in rotation: <strong>turbine shaft sections<\/strong>.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"symmetry-location\"><strong>Symmetry (Location)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"734\" height=\"562\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-19.png\" alt=\"Symmetry tolerance applied to a slot relative to datum A.\" class=\"wp-image-122970\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-19.png 734w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-19-300x230.png 300w\" sizes=\"(max-width: 734px) 100vw, 734px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-19.png\" data-fancybox=\"gallery-122726\" data-caption=\"Symmetry tolerance applied to a slot relative to datum A.\" aria-label=\"Open full image\"0><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-19.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Symmetry tolerance applied to a slot relative to datum A.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Similarly to concentricity, symmetry was <strong>removed from the ASME standard<\/strong> due to similar considerations, yet it remains a feature in the ISO standard.<\/p>\n\n\n\n<p>Symmetry requires that the median points of two opposing features must fall within a specified tolerance zone, which is a yellow block centered on a datum plane. In essence, the feature&#8217;s center plane needs to align with the datum center plane within a defined tolerance band.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> Equal spacing is important for function or balance: <strong>forked mounting surfaces <\/strong>(like the yoke of a universal joint) centered relative to a shaft axis for even load distribution.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"profile-of-a-surface-profile\"><strong>Profile of a Surface (Profile)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"647\" height=\"500\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-20.png\" alt=\"Profile of a surface tolerance applied to a freeform surface relative to datums A and B.\" class=\"wp-image-122982\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-20.png 647w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-20-300x232.png 300w\" sizes=\"(max-width: 647px) 100vw, 647px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-20.png\" data-fancybox=\"gallery-122726\" data-caption=\"Profile of a surface tolerance applied to a freeform surface relative to datums A and B.\" aria-label=\"Open full image\"1><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-20.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Profile of a surface tolerance applied to a freeform surface relative to datums A and B.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Profile of a surface defines a uniform 3D tolerance zone around the nominal surface (from basic dimensions) and references datums for orientation\/location. It\u2019s a similar envelope concept to flatness, but <strong>flatness<\/strong> is a form control with <strong>no datums<\/strong>, while <strong>surface profile<\/strong> supports simple or complex shapes with datum relationships.<\/p>\n\n\n\n<p>The difference is that the profile of a surface is also suitable for more complex shapes, creating a zone where all the points of the surface must lie in. Also, it needs a datum feature for reference.<\/p>\n\n\n\n<p><strong>Use example: <\/strong>Control of freeform\/curved surfaces where consistent shape matters: an aerodynamic panel staying within its designed profile for airflow.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"profile-of-a-line-profile\"><strong>Profile of a Line (Profile)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"640\" height=\"493\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-21.png\" alt=\"GD&amp;T profile of a line tolerance example with feature control frame.\" class=\"wp-image-122994\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-21.png 640w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-21-300x231.png 300w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-21.png\" data-fancybox=\"gallery-122726\" data-caption=\"GD&amp;T profile of a line tolerance example with feature control frame.\" aria-label=\"Open full image\"2><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-21.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>GD&amp;T profile of a line tolerance example with feature control frame.<\/em><\/figcaption><\/figure>\n\n\n\n<p>The profile of a line is to surface profile what <strong>straightness<\/strong> is to <strong>flatness<\/strong>. It specifies the minimum and maximum boundaries for the thinnest cross-section of a surface, effectively disregarding <strong>the third dimension.<\/strong><\/p>\n\n\n\n<p>This approach is useful when you need precise control of a surface\u2019s shape along specific directions without necessarily constraining the entire surface at once.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> Control of the <strong>curvature of a car body panel<\/strong> along a section to ensure smooth reflections and consistent assembly gaps.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"circular-runout-runout\"><strong>Circular Runout (Runout)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"753\" height=\"352\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-22.png\" alt=\"Circular runout tolerance applied to a shaft in GD&amp;T.\" class=\"wp-image-123006\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-22.png 753w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-22-300x140.png 300w\" sizes=\"(max-width: 753px) 100vw, 753px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-22.png\" data-fancybox=\"gallery-122726\" data-caption=\"Circular runout tolerance applied to a shaft in GD&amp;T.\" aria-label=\"Open full image\"3><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-22.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Circular runout tolerance applied to a shaft in GD&amp;T.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Circular runout defines the roundness of a feature&#8217;s individual cross-sections relative to the datum axis. Its tolerance zone, similar to circularity, is delineated by two concentric circles centered on the datum axis.<\/p>\n\n\n\n<p>However, it&#8217;s important to note that circular runout is not the same as circularity. In practice, <strong>runout is evaluated with the part rotating about the datum axis<\/strong>, while <strong>circularity<\/strong> is a static roundness check on a single cross-section.<\/p>\n\n\n\n<p>The similarity to circularity is in the fact that the diameter of the zone may vary at each cross-section, and likely does.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> Rotating parts must remain aligned and balanced: <strong>crankshaft journal<\/strong> circular runout relative to the main axis to prevent vibration and uneven bearing wear.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"total-runout-runout\"><strong>Total Runout (Runout)<\/strong><\/h2>\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"755\" height=\"358\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-23.png\" alt=\"\" class=\"wp-image-123018\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-23.png 755w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-23-300x142.png 300w\" sizes=\"(max-width: 755px) 100vw, 755px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-23.png\" data-fancybox=\"gallery-122726\" data-caption=\"Total runout tolerance applied to a shaft in GD&amp;T.\" aria-label=\"Open full image\"4><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-23.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>Total runout tolerance applied to a shaft in GD&amp;T.<\/em><\/figcaption><\/figure>\n\n\n\n<p>Total runout is similar to circular runout but inspects the entire surface of a feature, rather than individual cross-sections, relative to a datum axis. The tolerance zone is cylindrical and spans the feature&#8217;s full length.<\/p>\n\n\n\n<p>This control guarantees the surface is both round and straight along its entire axis, not merely at isolated sections.<\/p>\n\n\n\n<p><strong>Use example:<\/strong> Where full-length rotation quality matters. E.g., <strong>driveshaft total runout<\/strong> to ensure smooth rotation and avoid drivetrain vibration.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"modifiers\"><strong>Modifiers<\/strong><\/h2>\n\n\n<p>Modifiers are an important part of GD&amp;T. They allow for some additional <strong>bonus tolerance<\/strong> for tolerances depending on how close a feature is to its tolerance limits.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"maximum-material-condition\"><strong>Maximum Material Condition<\/strong><\/h3>\n\n\n<p>Maximum material condition or MMC for short is a condition whereby <strong>the workpiece has<\/strong> <strong>the most amount of material left after a cutout has been performed<\/strong>.<\/p>\n\n\n\n<p>For example, if a 10mm hole is specified with a tolerance of +\/-0.15mm, the minimum permissible hole size is 9.85mm. This 9.85mm dimension represents the MMC, as it leaves the most material.<\/p>\n\n\n\n<p>When using GD&amp;T positional tolerance without an MMC definition, the hole&#8217;s position must simply meet the specified tolerance (e.g., 0.2mm), regardless of its actual size. However, in practical applications, size is often critical, and this can be addressed by applying the MMC modifier.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><div class=\"wp-block-image__wrap\"><img decoding=\"async\" width=\"597\" height=\"481\" src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-24.png\" alt=\"\" class=\"wp-image-123030\" style=\"max-width:600px\" srcset=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-24.png 597w, https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-24-300x242.png 300w\" sizes=\"(max-width: 597px) 100vw, 597px\" \/><a class=\"wp-block-image__fancy-box-button\" href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-24.png\" data-fancybox=\"gallery-122726\" data-caption=\"GD&amp;T MMC example showing hole position tolerance with modifier.\" aria-label=\"Open full image\"5><img src=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/image-24.png\" class=\"wp-block-image__fancy-box-button-thumbnail wp-post-image\" alt=\"\" loading=\"lazy\" decoding=\"async\"><svg class=\"wp-block-image__fancy-box-button-icon\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"18\" height=\"18\" viewBox=\"0 0 18 18\" fill=\"none\" aria-hidden=\"true\">\r\n               <path d=\"M0 2V6H2V2H6V0H2C0.895 0 0 0.895 0 2ZM2 12H0V16C0 17.105 0.895 18 2 18H6V16H2V12ZM16 16H12V18H16C17.105 18 18 17.105 18 16V12H16V16ZM16 0H12V2H16V6H18V2C18 0.895 17.105 0 16 0Z\" fill=\"#092C47\"\/>\r\n             <\/svg><\/a><\/div><figcaption class=\"wp-element-caption\"><em>GD&amp;T MMC example showing hole position tolerance with modifier.<\/em><\/figcaption><\/figure>\n\n\n\n<p>When the MMC modifier is applied, a &#8220;bonus tolerance&#8221; is gained if the hole&#8217;s actual size is larger than the MMC. For instance, if the hole is 10.1mm, you gain an extra 0.25mm (10.1 &#8211; 9.85 = 0.25) of displacement allowance, in addition to the original positional tolerance.<\/p>\n\n\n\n<p>The primary purpose of bonus tolerance is to increase the allowable margin for error, which ultimately helps to reduce manufacturing costs.<\/p>\n\n\n\n<p><strong>Bonus tolerance = actual feature size &#8211; MMC size<\/strong><\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"least-material-condition\"><strong>Least Material Condition<\/strong><\/h3>\n\n\n<p>While less common than the maximum material condition, the least material condition still has practical applications. Its use case might not be immediately obvious.<\/p>\n\n\n\n<p>Consider a scenario with a hole near the edge of a plate. To prevent failure, you need to ensure sufficient material between the hole and the edge. <strong>If the hole&#8217;s actual size is smaller than the Least Material Condition (LMC) limit <\/strong>(e.g., 9.85 mm), the center of the hole can be closer to the edge by the difference. This difference contributes to a &#8220;bonus tolerance.&#8221;<\/p>\n\n\n\n<p><strong>Bonus tolerance = LMC size &#8211; actual feature size<\/strong><\/p>\n\n\n\n<p>For instance, if the LMC is 10.15 mm and the actual hole size is 9.85 mm, the bonus tolerance would be 0.3 mm (10.15 &#8211; 9.85 = 0.3), which is added to the allowed positional tolerance.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"regardless-of-feature-size\"><strong>Regardless of Feature Size<\/strong><\/h3>\n\n\n<p>Regardless of Feature Size (RFS) means the geometric tolerance remains constant, irrespective of the feature&#8217;s actual size, as long as it stays within its specified size limits. Unlike MMC or LMC, RFS<strong> does not offer any &#8220;bonus tolerance&#8221; <\/strong>when the feature deviates from its maximum or minimum material condition.<\/p>\n\n\n\n<p>RFS is the <strong>default condition<\/strong> in GD&amp;T. If no MMC or LMC symbol is present in the feature control frame, the interpretation automatically defaults to RFS. Consequently, many drawings do not explicitly call out RFS.<\/p>\n\n\n\n<p>RFS is typically chosen when the functional requirement necessitates <strong>tight control over both size and geometry simultaneously,<\/strong> regardless of any potential clearance. For instance, an alignment pin hole for an optical mount might require its position to be held to a tight tolerance, even if the hole is slightly oversized, as even a small positional shift could lead to misalignment.<\/p>\n\n\n<h2 class=\"wp-block-heading\" id=\"gdampt-tolerancing-guidelines\"><strong>GD&amp;T Tolerancing Guidelines<\/strong><\/h2>\n\n\n<ol class=\"wp-block-list\">\n<li><strong>GD&amp;T is not decoration<\/strong>\n<ul class=\"wp-block-list\">\n<li>If you\u2019re not sure it\u2019s functionally needed, don\u2019t apply it. Every GD&amp;T callout adds inspection cost.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Function first<\/strong>\n<ul class=\"wp-block-list\">\n<li>Tolerance only what affects fit, alignment, sealing, or performance. Leave non-critical features to general tolerances.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Keep the engineering drawing clean<\/strong>\n<ul class=\"wp-block-list\">\n<li>Place tolerances outside part boundaries, use visible true profiles, consistent grouping\/orientation\/spacing.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Don\u2019t over-specify<\/strong>\n<ul class=\"wp-block-list\">\n<li>Avoid process instructions unless essential. 90\u00b0 and coaxial conditions are often assumed unless stated otherwise.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Choose logical datums<\/strong>\n<ul class=\"wp-block-list\">\n<li>Base them on assembly\/inspection reality and sequence as they will be used (A\u2192B\u2192C).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Check feasibility<\/strong>\n<ul class=\"wp-block-list\">\n<li>Confirm process capability for the tolerances you asked for with manufacturing partners. Use MMC\/LMC where they reduce cost without hurting function.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p>GD&amp;T is how you translate design intent into parts that fit, seal, align, and move as intended, without overpaying for <a href=\"https:\/\/xometry.pro\/en\/articles\/standard-tolerances-manufacturing\/\">tolerances<\/a> you don\u2019t need.&nbsp;<\/p>\n\n\n\n<p>However, parts that don\u2019t fit, wear out faster, or require rework due to inaccuracies often cost far more in time and money. Wise use of geometric dimensioning and tolerancing can help you prevent these issues.<\/p>\n\n\n\n<p>Bellow, find the table of 17 common GD&amp;T symbols and download the free pdf.<\/p>\n\n\n    <div class=\"button-block\" style=\"text-align: left\">\r\n        <a href=\"https:\/\/xometry.pro\/wp-content\/uploads\/2025\/09\/geometric-dimensioning-and-tolerancing-guide.pdf\" target=\"\" class=\"button-block__btn btn_blue\">\r\n                        Download PDF!                     <\/a>\r\n    <\/div>\r\n","protected":false},"author":66,"featured_media":123059,"comment_status":"open","ping_status":"closed","template":"","categories":[],"c-tag-articles":[],"global-tag":[11],"class_list":["post-122726","articles","type-articles","status-publish","has-post-thumbnail","hentry","global-tag-cnc-machining"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v26.7 (Yoast SEO v27.3) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>GD&amp;T: Geometric Dimensioning &amp; Tolerancing Explained | Xometry Pro<\/title>\n<meta name=\"description\" content=\"Learn how to apply GD&amp;T correctly. 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