A geared slewing ring bearing is only half of the drive. The pinion that turns it carries the full drive torque through a handful of teeth, and if it does not match the bearing's gear, the bearing pays for it: noisy running, uneven tooth wear, broken teeth and, eventually, a damaged ring gear that is far more expensive to replace than the pinion. Yet the pinion is often bought last, from a different supplier, as an afterthought.
What has to match
A pinion is made to mesh with one particular ring gear. For the pair to run properly, these have to agree:
- Tooth size: the same diametral pitch (or module).
- Tooth form: the same pressure angle and tooth depth: full-depth or stub involute.
- Any profile shift on the ring gear, which the pinion has to suit.
- Face width and position, so the pinion engages the full width of the ring gear teeth.
- Centre distance and backlash, set at the high point of the ring gear (normally marked on the bearing).
- Strength: material and tooth hardening suited to the torque the drive actually delivers.
Buying the pinion with the bearing, from the people who designed the ring gear, is the simplest way to get all of these right.
Bore and mounting types
The other half of a pinion is how it fixes to the motor or gearbox. Common options:
- Keyed bore, with a keyway and set screws.
- Splined bore, coarse or fine, to suit the gearbox output shaft.
- Plain or threaded bore.
- Face-mounted (bolt-on), for a clean, quick installation to a flange output.
- Integral shaft (male shaft), with or without splines.
- With or without a hub.
Materials and protection
Pinions are commonly made from 4140 or 1045 steel, with induction-hardened teeth available for higher load and wear. Where corrosion is a concern, plating can be added.
Pinions from SlewPro
We keep more than 120 pinion designs on file in 2, 3 and 4 diametral pitch, with keyed, splined, plain, bolt-on and threaded bores and integral shafts, and we design new pinions to suit your bearing and drive, including pinions for other manufacturers' geared slewing rings. For linear axes, RackPro gear racks come with matching pinions as well.
Specifying a geared bearing? Read buying a geared slew bearing: you're buying half a drive system, then tell us your ring gear and motor shaft and we will supply the matching pinion. Request a quote.