# Print-in-place: captive wheel on a printed axle (Ø40 × 12)

> How do you 3D print a wheel already on its axle?

- Category: 3D printing › Print-in-place mechanisms
- Kind: Hardware
- Basis: Xem Studio design: revolved profiles, axle and wheel coaxial, one designed running gap of 0.40 mm
- Page: https://xemstudio.com/objects/print-in-place-captive-wheel-axle/ · JSON: https://xemstudio.com/api/geometry?object=print-in-place-captive-wheel-axle · Plain text: https://xemstudio.com/objects/print-in-place-captive-wheel-axle/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 40.0 | 40.0 | 20.0 |

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- 3D print in place — prints already assembled, moving, in one job. Drawn at true size with no printer tolerance added; the 0.40 mm running gaps are part of the design.
- Running gap 0.40 mm per side, 0.80 mm on diameter — part of the design, drawn as is. On the 45° faces the same 0.40 mm is measured square to the face (0.57 mm along the axis).
- Bed: the wheel lies flat, axle vertical. Both bodies start on the bed: the wheel on its full face, the axle on its 45° base cone inside the wheel's lower counterbore.
- Support while printing: the wheel's lower counterbore narrows upward at 45° over the axle's base cone; the axle's head widens upward at 45° inside the wheel's upper counterbore; nothing in either body overhangs more than 45°.
- Captured by the two cones: the axle's base cone (Ø12) cannot pass up through the Ø8.8 bore and its head (Ø13) cannot pass down through it, so the wheel cannot leave the axle.
- Freeing it: hold the axle stem and turn the wheel a full turn each way; push the axle up and down once to break the first layer apart.
- Motion: continuous rotation about the axle; free end play 0.57 mm each way and 0.40 mm radial, both from the geometry. No stops.
- Mount: an M3 screw through the axle's Ø3.4 hole, or press the stem into a Ø13 socket.

## Sizes

| key | value | what |
|---|---|---|
| gap_mm | 0.4 | running gap per side on every moving interface (radial, axial, under captured parts) — part of the design, not a tolerance |
| wheel_d_mm | 40.0 | wheel diameter |
| wheel_w_mm | 12.0 | wheel thickness |
| pin_d_mm | 8.0 | axle journal diameter |
| bore_d_mm | 8.8 | wheel bore (journal + 2 × 0.40) |
| head_d_mm | 13.0 | axle head diameter (45° cone from the journal) |
| base_d_mm | 12.0 | axle base-cone diameter on the bed |
| axial_play_mm | 0.57 | free end play each way from the drawn position (0.40 square to the 45° cones) |
| radial_play_mm | 0.4 | free radial play |
| rotation_deg | 360 continuous | wheel about the axle |
| stem_h_mm | 8.0 | axle stem above the wheel |
| screw_hole_d_mm | 3.4 | through hole along the axle (M3) |

## Where the files are

- Xem Studio: [Print-in-place mechanism design (geometry computed in the generator)](https://xemstudio.com/) — web — Xem Studio design

## Free STEP/STL (3 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/print-in-place-captive-wheel-axle/index.json · license: https://xemstudio.com/files/hardware/print-in-place-captive-wheel-axle/LICENSE.md

- print-in-place-captive-wheel-axle-assembly: [STEP](https://xemstudio.com/files/hardware/print-in-place-captive-wheel-axle/print-in-place-captive-wheel-axle-assembly.step) · [STL](https://xemstudio.com/files/hardware/print-in-place-captive-wheel-axle/print-in-place-captive-wheel-axle-assembly.stl) — The whole print as laid on the bed (2 bodies, already assembled); STEP keeps each moving body a separate solid
- print-in-place-captive-wheel-axle-wheel: [STEP](https://xemstudio.com/files/hardware/print-in-place-captive-wheel-axle/print-in-place-captive-wheel-axle-wheel.step) · [STL](https://xemstudio.com/files/hardware/print-in-place-captive-wheel-axle/print-in-place-captive-wheel-axle-wheel.stl) — Wheel Ø40 × 12 with a 45° V tyre groove and six Ø7 windows; bore Ø8.8 with 45° counterbores top and bottom
- print-in-place-captive-wheel-axle-axle: [STEP](https://xemstudio.com/files/hardware/print-in-place-captive-wheel-axle/print-in-place-captive-wheel-axle-axle.step) · [STL](https://xemstudio.com/files/hardware/print-in-place-captive-wheel-axle/print-in-place-captive-wheel-axle-axle.stl) — Printed axle: Ø8 journal, 45° base cone Ø12 on the bed, 45° head Ø13, stem to z 20, Ø3.4 through hole

## Questions

**How is the wheel held on the axle?**

By two 45° cones on the axle — a base cone Ø12 below the wheel's Ø8.8 bore and a head Ø13 above it — each 0.40 mm (square to the cone) from a matching counterbore in the wheel.

**How much end play does it have?**

0.57 mm each way: the 0.40 mm gap measured square to a 45° face is 0.40 / sin 45° along the axle.

## Fits with

- [Print-in-place: barrel hinge, three knuckles, folds 180° (48.8 mm)](https://xemstudio.com/objects/print-in-place-barrel-hinge-180/)
- [Print-in-place: seven-knuckle hinge on a captive through-pin (58.4 mm)](https://xemstudio.com/objects/print-in-place-multi-knuckle-hinge/)
- [Print-in-place: captive turntable with V-ridge retention (Ø80 platter)](https://xemstudio.com/objects/print-in-place-captive-turntable/)
- [Print-in-place: linear slider on a dovetail rail with end stops (100 mm)](https://xemstudio.com/objects/print-in-place-dovetail-slider/)
- [Print-in-place: articulated chain, 6 links, 20 mm pitch](https://xemstudio.com/objects/print-in-place-articulated-chain/)
- [Print-in-place: captive ball joint, Ø24 ball, limited cone](https://xemstudio.com/objects/print-in-place-ball-joint/)
- [Print-in-place: push button with flexure return and click](https://xemstudio.com/objects/print-in-place-push-button-flexure/)