Fit Test Generator

About Fit Test Generator

Fit Test Generator makes one small test print that measures how your own printer fits parts together: how much room parts need to slide, how much to press together, and how much smaller holes print than drawn. Print it, pick the tightest numbered step that fits on each piece, and the results are kept with your printer and filament.

The full guide: every step with pictures, examples, print settings, fixes and every setting.

Read the Fit Test Generator guide

Frequently asked questions

What do the numbers on the coupon mean?
On the strip and the ring they are hundredths of a millimetre of room per side: 15 means 0.15 mm. On the hole comb they are tenths of a millimetre added to the hole: +2 means 0.2 mm larger.
Why drill bits for the holes?
A steel shank has an exact diameter, so the hole comb measures your printer and not a second printed part. The smooth end of a 3 mm and a 6 mm drill bit works, or a 6 × 2 mm magnet; a hex key is too wide across its corners.
Do I need calipers?
No. You only pick the tightest step that fits. Every step is labelled on the coupon.
What if every step fits, or none does?
Results offers a coupon shifted the other way for that piece. Print it and pick again; nothing is saved until you do.
Is it free?
Yes. It runs in your browser. Signed in, the results are kept in your account; without an account they last for the visit.

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