30 : 45 · 1 : 1.5
STD S3M 30T & 45T, Custom Tooth Fit
When the presets aren't quite right for your printer: tooth clearance and backlash dialled in by hand, on the round-toothed STD S-series profile.
Sample · Timing Pulley Generator · printed & tested
STD 5M 20 and 100 tooth pulleys, printed and tested: a 1 : 5 reduction with an eight-spoke wheel
Printed and run on an S5M 690 belt: a 1 : 5 reduction to a 100-tooth wheel on eight spokes, whose top flange prints as a separate ring and glues on over 40 nubs, while the 20-tooth pulley prints its flanges in place.
Build it with your AI
Using the CheapCAD Tools connector, design a two-pulley timing belt drive: STD 5M belt (S5M), 10 mm wide, about 183.86 mm between centres, with 2 mm of extra face width beyond the belt. Pulley 1: 20 teeth, 5 mm bore, 0.2 mm print compensation, a hub 25 mm across and 10 mm tall with two M4 set screws in captured nuts, and printed flanges 2 mm thick reaching 4 mm past the teeth, the top flange printed in place on breakaway print supports. Pulley 2: 100 teeth, 5 mm bore, a hub 25 mm across and 10 mm tall with two M4 set screws in captured nuts, 8 spokes 6.9 mm wide on a 6 mm web round a 25 mm spoke hub, an 8.4 mm rim under the teeth, 10 mm fillets at the rim and 3 mm at the hub, and printed flanges 3 mm thick reaching 5 mm past the teeth, the top flange a separate part that locates on 40 gluing nubs 5 mm across and 3 mm tall. Check the design, apply any Auto-fix it suggests, then export both pulleys as STL and give me the download link.
Paste it into Claude, ChatGPT or any AI app with the CheapCAD Tools connector, and it designs this drive with you, checks it and hands you the files. How to connect your AI.
What's in this design
The drive
- STD S5M belt, 10 mm wide, 138 teeth (690 mm long)
- Centre distance 183.86 mm; ratio 20 : 100 (1 : 5)
Pulley 1
- 20 teeth
- 5 mm round bore
- Hub Ø25 × 10 mm, two M4 set screws in captured nuts
- Printed flanges, 2 mm thick, reaching 4 mm past the teeth; both print in place, the top one on breakaway supports for a 0.4 mm nozzle
- 0.2 mm print compensation in the STL
Pulley 2
- 100 teeth
- 5 mm round bore
- Hub Ø25 × 10 mm, two M4 set screws in captured nuts
- 8 spokes, 6.9 mm wide, under a 8.4 mm deep rim, on a 6 mm centre web, with 10 mm and 3 mm fillets
- Printed flanges, 3 mm thick, reaching 5 mm past the teeth; the top flange prints separately and locates on 40 alignment nubs
In the free STL zip
STD-5M-20T.stl— pulley 1, 20 teeth, without supportsSTD-5M-100T-P2-1flange.stl— pulley 2, 100 teethSTD-5M-20T-w-supports.stl— pulley 1 with breakaway supports under its top flange: print this oneSTD-5M-100T-P2-flange-only.stl— pulley 2's top flange, printed on its own
Free STLs are CC BY 4.0, exactly the design that was printed for the photos, with its print compensation (pulley 1 0.2 mm). Open the design to change anything, tune the fit for your printer, or download STEP, DXF, SVG and the belt.
Dimensions — 16 figures from the generator
| Pulley 1 | Pulley 2 | |
|---|---|---|
| Pitch diameter | 31.83 mm | 159.15 mm |
| Outside diameter | 31.08 mm | 158.40 mm |
| Outside diameter, as built | 30.68 mm | 158.40 mm |
| Root diameter | 27.54 mm | 154.86 mm |
| Groove depth | 1.77 mm | 1.77 mm |
| Pitch line differential | 0.38 mm | 0.38 mm |
| Belt width | 10.00 mm | 10.00 mm |
| Face width (belt + clearance) | 12.00 mm | 12.00 mm |
| Flange outside diameter | 38.68 mm | 168.40 mm |
| Flange past the OD | 4.00 mm | 5.00 mm |
| Minimum flange height | 2.15 mm≈ | 2.15 mm≈ |
| Flange inward of the groove | — | 8.40 mm |
| Minimum flange overlap | — | 3.00 mm≈ |
| Belt | 138 teeth · 690.00 mm | |
| Centre distance | 183.86 mm | |
| Drive ratio | 20 : 100 · 1 : 5 | |
Read from the generator's Dimensions panel for this design, which opens with no warnings.
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