Worm and Wheel Must Be Made Together
A worm drive gives a big speed reduction at a right angle in a single stage, and at low lead angles it's self-locking — the worm drives the wheel, but the wheel can't drive back. The catch is that the worm and the wheel are a matched pair: they must share the same module, lead, pressure angle and centre distance. Make one without the other and they won't mesh. We machine them as a set, classically a hardened steel worm running on a bronze wheel so the dissimilar metals run cool and wear slowly.
Custom Worm Gear Specifications
| Attribute | Capability |
|---|---|
| Set | Worm shaft + worm wheel, matched |
| Starts / ratio | Single or multi-start; high single-stage reduction |
| Worm material | Hardened steel (e.g. 4140) or stainless |
| Wheel material | Phosphor / aluminium bronze (plastic for light duty) |
| Self-locking | Advised on, depends on lead angle & friction |
| Bore & keyway | To shaft fit; keyway to DIN 6885 / ISO 773 |
Ratio, Lead Angle & Self-Locking — the Numbers That Matter
Two things trip people up on worm drives: how the ratio works, and whether it self-locks. Both come down to the worm's number of starts and its lead angle:
| Question | Rule |
|---|---|
| Reduction ratio | = wheel teeth ÷ worm starts (not teeth ÷ teeth) — e.g. a 40-tooth wheel on a single-start worm = 40:1 |
| Self-locking? | Yes when the lead angle ≲ 5° (strictly, lead angle ≤ friction angle) — the worm drives the wheel but the wheel can't back-drive |
| Single-start worm | Highest ratio & strongest self-locking, lower efficiency |
| Multi-start worm (2–4) | Higher efficiency & smoother, but lower ratio and usually not self-locking |
| Efficiency | Falls as lead angle drops — self-locking sets trade efficiency for holding power |
So if you need the drive to hold position without a brake (a lift, jack, damper or valve actuator), you want a low-lead-angle single-start set; if you need efficiency, a multi-start worm. Tell us the ratio you need and whether it must self-lock, and we'll design the starts and lead angle to suit.
How We Make / Reproduce a Worm Set
- From specs: ratio, centre distance and shaft sizes — we derive module, lead and tooth count.
- From a sample: we recover module, lead/lead angle, starts, tooth count, pressure angle and centre distance from your worn worm and wheel (see reverse engineering).
- Pair the materials: hardened steel worm + bronze wheel for low friction and long life.
Material Pairing
The classic worm-drive pairing is a hardened steel worm on a phosphor- or aluminium-bronze wheel — the dissimilar materials reduce friction and let the cheaper wheel wear in preference to the worm. For light duty a plastic wheel is possible. Mesh, bore and keyway are verified on inspection.
Worn worm or stripped wheel? Send both parts if you can — having the pair lets us confirm module, lead and centre distance precisely and machine a matched replacement set. No drawing required. See also our discontinued gear guide.
Frequently Asked Questions
Yes — and it's the right way. The pair must share module, lead, pressure angle and centre distance, so we machine them together: typically a hardened steel worm on a bronze wheel.
Yes — we recover module, lead/lead angle, starts, tooth count, pressure angle and centre distance from the worn pair and machine a meshing set. No drawing needed.
At low lead angles the worm drives the wheel but the wheel can't back-drive — holding position without a brake. Whether a set self-locks depends on lead angle and friction; we can advise.
Hardened steel or stainless worm with a phosphor/aluminium-bronze wheel; plastic wheel for light duty.
Quote a Worm Gear Set
Worn pair, ratio or drawing — all accepted. Reply in 24h.