Can I order a gear with a smaller bore than the catalog size?
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- Issue Time
- Oct 21,2026
Can I order a gear with a smaller bore than the catalog size?
A smaller bore can be specified on a new custom gear, subject to manufacturing review. PairGears lists customized bores and shaft features among its capabilities. An existing finished bore cannot be made smaller by removing more material. Request a new part with the required bore, or have an engineered sleeve arrangement reviewed for the application.
Distinguish a new bore specification from rework
The PairGears custom cylindrical gear service lists bores, keyways and other shaft features made to requirements. Supply the exact finished bore diameter and tolerance for feasibility review; a general customization listing does not establish every available size or fit.
For example, if an existing gear has a 25 mm bore and the shaft is 20 mm, further boring or reaming will not close the gap. The practical choices are a newly manufactured gear with the specified interface or a separately designed adaptation. These dimensions are an example, not a catalog listing.
Define how the smaller shaft will transmit torque
State shaft size and tolerance, bore fit, torque, speed, load cycle, axial location and any key, spline or clamp arrangement. Confirm the mating gear data so that changing the shaft interface does not accidentally change the tooth specification.
If a sleeve is proposed, review the gear-to-sleeve and sleeve-to-shaft interfaces separately. The design must address torque transfer, axial retention, runout, wall thickness and operating conditions. A sleeve chosen only by nominal diameters is not a verified mounting solution. Obtain an approved assembly drawing before manufacture.
Check the finished fit after the manufacturing route is set
Specify the locating face and bore datum, required dimensional checks and the relationship between the finished bore and gear teeth. Agree when heat treatment and finishing occur, and verify fit and runout in the final delivery condition.
Request a dimensional report for the relevant interface. A hardness or metallographic report provides different evidence and does not confirm bore size or shaft fit. The PairGears inspection-report guide helps separate those checks. Confirm the proposed route and acceptance criteria before ordering.
