Air Die Grinder Kit 1/4 in Collet with 10 Stones

Straight-body air die grinder kit built around the Ingersoll Rand 307B. The 0.25 hp air motor runs to 28,000 rpm free speed on a 1/4 in collet, which is the working range you want for carbide burrs and mounted stones. The tool weighs 0.7 lb, so you can hold it steady over a valve body for several minutes without your hand cramping up. The kit ships with the grinder, 10 mounted grinding stones, two collet wrenches and a blow-molded case. An air compressor is not included.

On a transmission bench this is the tool that cleans up the parts a rebuild kit will not fix. Knocking the burrs off a valve body casting after you pull a stuck valve, deburring the bolt-hole raised edges on a separator plate so the plate seats flat, breaking the sharp edge on a case bore before you slide a new bushing in, and cutting scored material off a pump housing face are all jobs it handles. It also cleans weld splatter and rust off crossmembers, mount brackets and cooler-line hard tubing when you are putting a unit back under a truck.

The throttle is self-locking, so the grinder stays disengaged until you deliberately release the lever - useful when you set the tool down on a bench covered in loose valves and springs and do not want it walking off under air pressure. Exhaust is routed out the front and the housing is aluminum over precision ball bearings, which is why these hold rpm instead of losing speed as the vanes wear. The straight configuration reaches into a bellhousing or down a case bore that a right-angle grinder cannot get into.

Air tools live or die on clean, oiled air. Run it off an inline oiler or put a few drops of air tool oil in the inlet at the start of each shift, and drain your compressor tank so water does not reach the vanes. Aluminum shavings from a valve body are conductive and get everywhere - blow the casting out and wash it before it goes back together.