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Best practices for dimensioning parallelism from a datum

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Hi, how do you handle dimensioning parallelism for critical parts? I’m debating between using basic dimensions with profile tolerances vs. a combination of ± tolerance and parallelism control. What methods and standards do you rely on for ensuring accurate alignment? Any specific guidelines or best practices you follow in your workflow?

Solved by Joao Clemencio

Hi Gregory,

When it comes to dimensioning parallelism, both methods—using basic dimensions with profile tolerances and a combination of ± tolerance with parallelism control—have their place, but here's how I typically approach it:

Basic Dimensions with Profile Tolerances:
When to Use: Best for high-precision parts where you need tight control over form, orientation, and size in one go.
Why: Profile tolerances give you more comprehensive control, making sure everything aligns as it should without piling on separate tolerances for each feature.
Standards: I follow ASME Y14.5 for this, as it’s the gold standard in GD&T. It’s also aligned with ISO 1101 internationally.

± Tolerance with Parallelism Control:
When to Use: Ideal for simpler parts or when you’re mainly concerned with the size and basic alignment.
Why: It’s more straightforward and easier for teams familiar with traditional tolerancing methods. Plus, inspection can often be simpler with standard tools.
Standards: Still sticking with ASME Y14.5, but ISO 2768 is good if you’re working with general tolerances.

If precision is critical and you’re dealing with complex geometry, go with basic dimensions + profile tolerances. For simpler parts, ± tolerance with parallelism control should work fine and might save time and effort.

Hope this helps! Let me know if you need more details or have other questions!

    • G

      Hi, how do you handle dimensioning parallelism for critical parts? I’m debating between using basic dimensions with profile tolerances vs. a combination of ± tolerance and parallelism control. What methods and standards do you rely on for ensuring accurate alignment? Any specific guidelines or best practices you follow in your workflow?

      0
    • Xometry Engineer

      Hi Gregory,

      When it comes to dimensioning parallelism, both methods—using basic dimensions with profile tolerances and a combination of ± tolerance with parallelism control—have their place, but here’s how I typically approach it:

      Basic Dimensions with Profile Tolerances:
      When to Use: Best for high-precision parts where you need tight control over form, orientation, and size in one go.
      Why: Profile tolerances give you more comprehensive control, making sure everything aligns as it should without piling on separate tolerances for each feature.
      Standards: I follow ASME Y14.5 for this, as it’s the gold standard in GD&T. It’s also aligned with ISO 1101 internationally.

      ± Tolerance with Parallelism Control:
      When to Use: Ideal for simpler parts or when you’re mainly concerned with the size and basic alignment.
      Why: It’s more straightforward and easier for teams familiar with traditional tolerancing methods. Plus, inspection can often be simpler with standard tools.
      Standards: Still sticking with ASME Y14.5, but ISO 2768 is good if you’re working with general tolerances.

      If precision is critical and you’re dealing with complex geometry, go with basic dimensions + profile tolerances. For simpler parts, ± tolerance with parallelism control should work fine and might save time and effort.

      Hope this helps! Let me know if you need more details or have other questions!

      0
      Reply
Best practices for dimensioning parallelism from a datum
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