20 : 30 · 1 : 1.5
L 20T & 30T, ½" & ¾" Keyed Bores
The ⅜" L pitch for heavier inch-sized machines: ½" and ¾" bores with ⅛" and 3/16" keyways, and a 1/4-20 set screw on the larger hub.
Sample · Timing Pulley Generator
XL timing pulleys with inch bores and inch set screws
Imperial down to the hardware: an XL belt, ¼" and ⅜" shafts, and #8-32 and #10-24 set screws in captured nuts.
Build it with your AI
Using the CheapCAD Tools connector, design a two-pulley timing belt drive: XL belt, about 120 mm between centres, set screws in captured nuts. Pulley 1: 20 teeth, ¼" bore, a hub 18 mm across and 9 mm tall with a #8-32 set screw, and printed flanges with the top flange printed as a separate part. Pulley 2: 30 teeth, ⅜" bore, a hub 22 mm across and 10 mm tall with a #10-24 set screw. 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
- XL (0.200″ pitch) belt, 10 mm wide, 73 teeth (370.84 mm long)
- Centre distance 121.65 mm; ratio 20 : 30 (1 : 1.5)
Pulley 1
- 20 teeth
- ¼″ (6.35 mm) round bore
- Hub Ø18 × 9 mm, two #8-32 set screws in captured nuts
- Printed flanges, 1.5 mm thick, reaching 3 mm past the teeth; the top flange prints separately
Pulley 2
- 30 teeth
- ⅜″ (9.525 mm) round bore
- Hub Ø22 × 10 mm, two #10-24 set screws in captured nuts
In the free STL zip
Imperial-XL-20T+flange.stl— pulley 1, 20 teethImperial-XL-30T-P2.stl— pulley 2, 30 teethImperialXL-20T-3DP-upper-flange.stl— pulley 1's top flange, printed on its own
Free STLs are CC BY 4.0, printed size without print compensation. Open the design to change anything, tune the fit for your printer, or download STEP, DXF, SVG and the belt.
Dimensions — 14 figures from the generator
| Pulley 1 | Pulley 2 | |
|---|---|---|
| Pitch diameter | 32.34 mm | 48.51 mm |
| Outside diameter | 31.83 mm | 48.00 mm |
| Root diameter | 28.53 mm | 44.70 mm |
| Groove depth | 1.65 mm | 1.65 mm |
| Pitch line differential | 0.25 mm | 0.25 mm |
| Belt width | 10.00 mm | 10.00 mm |
| Face width (belt + clearance) | 12.90 mm | 12.90 mm |
| Minimum face width | 11.00 mm | 12.80 mm |
| Flange outside diameter | 37.83 mm | — |
| Flange past the OD | 3.00 mm | — |
| Minimum flange height | 1.00 mm | — |
| Belt | 73 teeth · 370.84 mm | |
| Centre distance | 121.65 mm | |
| Drive ratio | 20 : 30 · 1 : 1.5 | |
Read from the generator's Dimensions panel for this design, which opens with no warnings.
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