# Printer calibration coupons: hole, pin, nut-trap, T-slot tongue and bearing-pocket gauges

> How do I calibrate my 3D printer so holes and shafts fit the files in this library?

- Category: Stirling engines › Generators & instruments
- Kind: Hardware
- Basis: Every file on this site assumes: pivot hole = pin + 0.2, press fit = pin − 0.05, bearing pocket = OD + 0.2 (OD + 0.3 above 20 mm), nut trap = AF + 0.3, T-slot tongue 5.8 in a 6 mm slot. These coupons find your printer's offset so those assumptions hold
- Page: https://xemstudio.com/objects/printer-calibration-coupons/ · JSON: https://xemstudio.com/api/geometry?object=printer-calibration-coupons · Plain text: https://xemstudio.com/objects/printer-calibration-coupons/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses

## Notes

- Print the Ø3 hole gauge; push a 3 mm dowel pin through each: the first that slips freely is your 'clearance', the last that needs a tap is your 'press'. If 3.2 slips and 3.0 presses, your printer matches the library and nothing needs changing. If it takes 3.4 to slip, set a horizontal hole compensation of +0.2 mm in the slicer (or scale holes in CAD).
- Pin gauge: the 3.0 pin should enter a 623 bearing bore with finger pressure; if only 2.9 does, external features print fat: set XY compensation −0.05. Nut gauge: the M3 nut should push into the 5.8 AF trap and not fall out of 5.6. Tongue gauge against real 2020: 5.8 slides, 6.0 binds. Pocket gauge: a 608 presses into 22.2 with a thumb and holds.
- Do this once per printer and filament (PETG shrinks less than PLA, ABS more); write the two numbers (hole offset, XY offset) in your slicer profile. After that every STEP and STL on xemstudio.com fits as drawn, and an AI agent designing around these sheets can use the stated clearances without guessing.

## Sizes

| gauge | what it tests | pass condition |
|---|---|---|
| hole 2.8–3.6 | Ø3 pivots / M3 clearance | 3.0 press, 3.2 slip, 3.4 clearance |
| hole 4.8–5.6 | Ø5 shafts | 5.0 press, 5.2 slip |
| hole 7.8–8.6 | Ø8 shafts | 8.0 press, 8.2 slip |
| pin 2.8–3.2 / 4.8–5.2 | printed pins into bearings | 3.0 / 5.0 enters finger-tight |
| nut trap M3/M4 | captive nuts | 5.8 / 7.2 AF snug |
| tongue 5.6–6.0 | T-slot brackets | 5.8 slides in 2020 |
| pocket 10/16/22 | 623 / 625 / 608 pockets | +0.2 thumb press |

## Where the files are

- Wikipedia: [Engineering tolerance](https://en.wikipedia.org/wiki/Engineering_tolerance) — web — CC BY-SA 4.0 (text)
- Prusa: [Knowledge base: XY size compensation](https://help.prusa3d.com/article/xy-size-compensation_125045) — web — Prusa KB (verify at link)
- Long Earth Society: [Engine and rig builds](https://longearthsociety.com/engineering/) — web, video — LES site

## Free STEP/STL (8 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/printer-calibration-coupons/index.json

- hole-gauge-m3-2-8-to-3-6: [STEP](https://xemstudio.com/files/hardware/printer-calibration-coupons/hole-gauge-m3-2-8-to-3-6.step) · [STL](https://xemstudio.com/files/hardware/printer-calibration-coupons/hole-gauge-m3-2-8-to-3-6.stl) — hole gauge for Ø3 pins/screws: 2.8–3.6 in 0.1 steps (find press, slip and clearance)
- hole-gauge-m5-4-8-to-5-6: [STEP](https://xemstudio.com/files/hardware/printer-calibration-coupons/hole-gauge-m5-4-8-to-5-6.step) · [STL](https://xemstudio.com/files/hardware/printer-calibration-coupons/hole-gauge-m5-4-8-to-5-6.stl) — hole gauge for Ø5 shafts: 4.8–5.6
- hole-gauge-m8-7-8-to-8-6: [STEP](https://xemstudio.com/files/hardware/printer-calibration-coupons/hole-gauge-m8-7-8-to-8-6.step) · [STL](https://xemstudio.com/files/hardware/printer-calibration-coupons/hole-gauge-m8-7-8-to-8-6.stl) — hole gauge for Ø8 shafts: 7.8–8.6
- pin-gauge-2-8-to-3-2: [STEP](https://xemstudio.com/files/hardware/printer-calibration-coupons/pin-gauge-2-8-to-3-2.step) · [STL](https://xemstudio.com/files/hardware/printer-calibration-coupons/pin-gauge-2-8-to-3-2.stl) — printed pin gauge 2.8–3.2: which prints to a true Ø3 hole in a bearing?
- pin-gauge-4-8-to-5-2: [STEP](https://xemstudio.com/files/hardware/printer-calibration-coupons/pin-gauge-4-8-to-5-2.step) · [STL](https://xemstudio.com/files/hardware/printer-calibration-coupons/pin-gauge-4-8-to-5-2.stl) — printed pin gauge 4.8–5.2 (625 bearing bore test)
- nut-trap-gauge-m3-m4: [STEP](https://xemstudio.com/files/hardware/printer-calibration-coupons/nut-trap-gauge-m3-m4.step) · [STL](https://xemstudio.com/files/hardware/printer-calibration-coupons/nut-trap-gauge-m3-m4.stl) — nut-trap gauge: M3 at 5.5/5.7/5.9 AF, M4 at 7.0/7.2/7.4
- extrusion-tongue-gauge-6mm: [STEP](https://xemstudio.com/files/hardware/printer-calibration-coupons/extrusion-tongue-gauge-6mm.step) · [STL](https://xemstudio.com/files/hardware/printer-calibration-coupons/extrusion-tongue-gauge-6mm.stl) — T-slot tongue gauge: 5.6 / 5.8 / 6.0 mm tongues for a 6 mm slot
- bearing-pocket-gauge-623-625-608: [STEP](https://xemstudio.com/files/hardware/printer-calibration-coupons/bearing-pocket-gauge-623-625-608.step) · [STL](https://xemstudio.com/files/hardware/printer-calibration-coupons/bearing-pocket-gauge-623-625-608.stl) — bearing pocket gauge: Ø10.0/10.2/10.4 (623), Ø16.0/16.2/16.4 (625), Ø22.0/22.2/22.4 (608), 6 deep

## Questions

**What tolerance do the files on this site assume?**

Pivot holes pin + 0.2 mm, press fits pin − 0.05, bearing pockets OD + 0.2 (0.3 above 20 mm), nut traps AF + 0.3, T-slot tongues 5.8 mm. Print the gauges once to confirm your printer lands there.

**My holes print too small; what do I change?**

Measure which gauge hole slips over a 3 mm pin; the difference from 3.2 is your offset. Set it as hole/horizontal compensation in the slicer (+0.1 to +0.3 is typical for PLA on a 0.4 nozzle).

**Why do printed holes come out undersize?**

Extrusion width rounding on curves, plastic shrink and the slicer's arc approximation all push material inward; outside features come out fat by a similar amount. A one-time XY compensation fixes both.

## Fits with

- [Ball bearings, 683 to 6210 and flanged F6xx (ISO 15)](https://xemstudio.com/objects/ball-bearings-metric/)
- [Dowel pins, 2–6 mm (ISO 2338 / DIN 6325)](https://xemstudio.com/objects/dowel-pins-metric/)
- [Hex nuts, M2–M8 (ISO 4032)](https://xemstudio.com/objects/hex-nuts-metric/)
- [T-slot attachments: slide-in and drop-in T-nuts, corner brackets, gussets, end caps, slot covers, feet, hole plates](https://xemstudio.com/objects/t-slot-brackets-and-nuts/)
- [Heat-set threaded inserts, M2–M6 (for 3D prints)](https://xemstudio.com/objects/heat-set-inserts/)
- [Can-engine printed kit: can caps, diaphragm clamps, displacer guides, crank stands, CD/platter hubs, syringe cradles](https://xemstudio.com/objects/can-engine-printed-kit/)