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[Charlotte D.]

Hi, I’m working on a small metal housing (around 120 × 80 × 40 mm) that will be 3D printed with DMLS for a sensor module. It needs threaded M3 screw holes and a flat mating surface. For those who’ve handled similar applications, what tolerances should I expect on the printed holes, and would you usually machine the flat surface afterwards to get a reliable seal?

[Morgan E.]

For DMLS, expect as-printed hole diameters to be undersized by roughly 0.1–0.2 mm, depending on material and machine. Threaded holes are almost always better to drill and tap after printing, especially for M3 and smaller, since the powder bed process can leave rough surfaces and internal porosity that makes tapping difficult.

[Amy C.]

Yes, agreed, I always use a slightly undersized “as-printed” hole, like 2.7 mm for M3, then drill/tap to spec afterward. That avoids stressing the part and ensures threads aren’t loose or damaged.