GT2 Timing Pulley Ratio Set: 16T, 20T, 30T, 36T and 40T, 5 mm Bore, 6 mm Belt, Aluminium (16 Pulleys)

A GT2 pulley ratio set is a spread of 2 mm-pitch timing pulleys in different tooth counts on one bore size, bought together so that a belt-driven axis can be geared, tested and re-geared without ordering a new pulley for every attempt.

Functionally equivalent to: Gates PowerGrip GT2 and SDP/SI 2 mm-pitch timing pulleys (USD 12–30 each) · Misumi GT2 series. Same 2 mm pitch, 6 mm belt width and grub-screw bore.
Compatible replacement part. We are not affiliated with, authorised by or endorsed by these manufacturers, and this is not an OEM part — check the specification below against your application before ordering.

Belt-drive design is mostly guessing the ratio, then waiting a fortnight for the pulley you should have ordered. This set covers the five tooth counts a small machine actually uses — 16, 20, 30, 36 and 40 — all on a 5 mm bore, so you can try every sensible ratio on the bench in an afternoon instead of one per order.

What can you use it for?

• Choosing the reduction on a belt-driven 3D printer or CNC axis by testing, not calculating
• Gearing down a NEMA 17 for more torque or up for more speed on the same motor
• Closed-loop and camera-gantry builds where the ratio is not known until it runs
• Rebuilding a printer's X/Y drive with matched 20T idlers and drive pulleys
• Teaching belt-drive ratios with real hardware rather than a diagram

Who is it for?

Printer and CNC builders, robotics teams and makerspaces who iterate on mechanics and would rather own every common ratio than wait two weeks for the right one.

Compatibility

• Belt: GT2 / 2GT, 2 mm pitch, 6 mm wide — the standard on Ender, Prusa, Voron and most desktop machines
• Shaft: 5 mm, the NEMA 17 standard; two M4 grub screws per pulley
• Mixes with GT2 idlers and open-ended GT2 belt
• Not compatible with 3M, 5M or HTD belts — the tooth profile differs

Specifications

What's in the box

• GT2 Pulley Ratio Set (5 mm bore): 5 × 16T, 5 × 20T, 2 × 30T, 2 × 36T, 2 × 40T — 16 aluminium pulleys with grub screws

Shipping and returns

Ships from our warehouse in Singapore with tracking. Parts and accessories: free standard shipping on orders over $25 ($4.99 below) to Canada, the UK, EU, Japan, Korea, Australia and most other countries, 5–15 days; to the United States at carrier cost from $27.99 (SingPost) or $109.99 (DHL Express). Assembled robot-arm kits over 2 kg are built and calibrated to order in Singapore (dispatch in 7–10 business days) and ship worldwide at carrier cost: SingPost Speedpost Priority from $124.99 (10–14 business days) or DHL Express from $229.99 (3–5 business days), shown at checkout. 7-day returns; defective items are replaced or refunded with shipping covered. Import duties, where charged by your country, are paid by the recipient.

Frequently asked questions

What ratios can I actually make?

Any pair from 16 / 20 / 30 / 36 / 40 teeth. Common ones: 20:40 gives 2:1 reduction, 16:40 gives 2.5:1, 20:20 gives 1:1 for a simple belt transfer, 16:20 gives a light 1.25:1.

Why are there five of the small pulleys and only two of the large?

Small pulleys get used in pairs and as idlers, so you run out of them first; the large ones are usually one per axis.

Is 5 mm bore right for my motor?

Yes if you are driving a NEMA 17 — that is the standard shaft. NEMA 23 and many spindles use 8 mm; we list the 8 mm bore pulleys separately.

Do the grub screws hold on a flatted shaft?

Better than on a round one. Align one grub screw with the flat on the motor shaft; on a fully round shaft, use both screws and a drop of threadlocker.

Are these Gates pulleys?

No. They are aluminium GT2-profile pulleys sold under our own ArmDojo brand, dimensionally compatible with Gates PowerGrip GT2 and Misumi GT2 belts and pulleys. We are not affiliated with those manufacturers.