Precision V-Block and Clamp Pair for Shaft Runout Checks

This is a matched pair of case hardened and ground V-blocks with clamps, HHIP part number 3402-0112. Each block measures 2.5 x 2.75 x 2 inches and carries a centered 90 degree vee that is held parallel and square to every other face within 0.0003 inch. That squareness is the whole point: if the two vees do not sit at the same height and the same angle, every runout number you take off them is fiction. The stepped groove lets you move the clamp to suit the diameter you are holding, and the blocks take round work up to 2 inches across or square work up to 1-7/16 inches.

Using them to check a shaft is straightforward. Set both blocks on a flat reference surface with the vees in line, then lay the shaft in so the two vees carry it at its bearing journals rather than anywhere the splines or a snap ring groove would rock it. Bring a dial indicator down on the shaft between the blocks, zero it, and turn the shaft one full revolution by hand while you watch the needle. The spread between the high and low reading is total indicator reading. Walk the indicator along the shaft and repeat at a few stations, because a shaft can read true at one point and out at another.

The failure this catches is a bent input or output shaft, which is easy to miss and expensive to ignore. A shaft that has been through a hard converter or planetary failure, or one that got leaned on with a pry bar during teardown, can be out by a few thousandths and still look perfectly straight on the bench. Put it back in and it chews sealing rings, wears the support bushing oval, and pushes the unit right back into the shop. A few minutes in the vees tells you whether the shaft is reusable before you build a good unit around a bad one.

Check your shaft before ordering: the vees hold up to 2 inches in diameter, which covers most passenger and light truck transmission shafts, but larger heavy duty shafts will not seat in them.