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Fit Test Coupon Generator (OwlCAD)

One test print that tells you how much clearance your printer really needs for a joint

Fit Test Coupon Generator (OwlCAD) is a free browser tool for finding the right clearance before you print hinges, lids or snap-fits. The customizers and the editor are free; only OwlCAD's AI features need the Pro subscription. Exports STL and 3MF; no account needed. Last checked 16 October 2026.

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Opens owlcad.com

At a glance

Price: The customizers and the editor are free; only OwlCAD's AI features need the Pro subscription
Runs on: Browser
Exports: STL, 3MF
Multicolor: No, single color
Account: Not needed
Open source: No
Skill level: Beginner: fill in a form
Best for: Finding the right clearance before you print hinges, lids or snap-fits
Selling prints: Allowed OwlCAD's terms include commercial use on every plan, the free tier included: you may sell prints, sell or license the files and use them in a product, with no royalty and no attribution required.
How we checked: Opened the generator Customizer opened in a browser with no account: the default pin-and-hole coupon rendered in 3D with all settings; pricing and terms read
Checked by: Mike Janssen
Last checked: 16 October 2026

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Sources: Fit test coupon customizer, OwlCAD pricing, OwlCAD terms (checked 16 October 2026)

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About this generator

The Fit Test Coupon Generator is one of the free customizers in OwlCAD, a browser-based parametric CAD tool. It makes a tolerance test: a plate with a row of holes or slots stepping through a clearance range, each one engraved with its value, plus a gauge pin at the nominal size. The first hole the pin enters cleanly is your real clearance.

How much slack a printed joint needs depends on your printer, filament and slicer, not on the design, so one plate replaces printing a part twice. You choose pin and hole or tab and slot, the nominal size (1 to 100 mm), the number of stations (2 to 12), the first clearance and the step between them, and the plate thickness. The page suggests running it once round and once flat, because the two give different results.

It runs in the browser with no account and costs nothing; only OwlCAD's AI features are paid. It is one of 35 free OwlCAD customizers, and you can open the result in the full editor if you want to change more. Its terms give you full commercial rights to what you make, the free plan included.