81 Piece SAE and Metric Tap and Die Thread Repair Set

Every transmission that comes across the bench has threads somebody already ruined. Pan rail holes in a cast-aluminum case get cross-threaded when a bolt goes in crooked. Cooler line fittings gall into the case and drag the first two threads out with them. Valve body bolts, extension housing bolts, bellhousing bolts, shift cable bracket studs - they all thread into soft metal, and most of the time the hole is not gone, it is just dirty or slightly pulled. A tap run through it by hand puts it right in about ninety seconds. That is what this 81-piece set is for.

Coverage is SAE #4 through 1/2 in. and metric M3 through M12, in both coarse and fine pitch, which is the range that covers essentially all automatic transmission case, pan and valve body hardware plus the bolts around the bellhousing and crossmember. There are 68 taps and dies in the set, along with dual thread pitch gauges so you can identify a fastener before you cut anything. Taps and dies are GCr15 bearing steel heat treated to as much as 60 HRC, so they hold an edge cutting aluminum and cast iron and do not deform under torque from a T-handle.

The two jobs this does on a rebuild are chasing and cutting. Chasing is the common one: run the matching tap in by hand with cutting oil, back it off a half turn every full turn to break the chip, and keep going until it spins freely, then blow the hole out with air before the case goes back together. Chips left in a blind hole bottom the bolt and give you a false torque reading, which is how pan rails end up leaking after a rebuild. Cutting new threads is the other job - drill, then tap - when you are adding a temperature sender bung, a pressure tap for a test gauge, or a bracket that was not there from the factory. The dies handle the outside work: cleaning up a stud, a cooler line nipple, or a bolt whose first threads got beat over.

One caution. A tap and die set cleans and cuts threads. It does not fix a hole that is already stripped out - if the bolt spins with no resistance, the aluminum is gone and you need a wire insert kit instead. Use this set before it gets to that point, and most cases never need one.