Replacement stem driver (plastic insert / coupler) for Kohler(R) Rite-Temp(R) shower trim kit (faucet handle) and likely others.

The author of this file is not affiliated with Kohler(R), all trademarks are the property of their respective owners and used nominatively.

The stem driver is a small plastic bit that couples the shower handle to a mating feature on the valve stem (a square peg/key on the actual valve in the wall). On my said unit, this coupler broke (corners cracked) at just over a year old (note the warranty period is 1 year). Judging by the reviews for this unit (9 reviews, all 1-2-star and complaining of a cracked stem driver as of 7/14/2024) this is a common problem: https://www.kohler.com/en/support/find-a-service-part/shop-parts/assembly-handle-1332384?skuId=1332384-BL

Dimensions in the STLs and OpenSCAD default values are for the K-TS22028-4-BN / K-TS22028-4-BL / K-TS22028-4-CP / K-TS22028-4-SL. It is likely to work for other Kohler faucet handles by adjusting the length or other geometry values to fit.

When replacing the part, be sure to transfer any hardware, including square gasket and O-ring, from the old part.

The STLs are for the part "as-shipped" (original geometry) and for a modestly lengthened version. On my shower, the original stem driver seemed a bit too short; it had to be blind-mated since it did not engage before the threads on the handle assembly caught, and even when cranked down all the way seemed to barely engage. The lengthened version of the .STL adds 3/8 inches to make assembly easier, especially if the valve stem is recessed into the wall a ways. The mating key of both are slightly oversized (there's room) for additional strength.