I bought a reamer kit to install throttle shaft bushings in the throttle body. The throttle body is made of cast steel and eventually wears. This kit comes with the reamer and four 5/16" bushings. Here it is on ebay:
It is assumed that the reamer in the kit will be used with machinery to align the reamer properly. I don't have this equipment but because the reamer shaft is 5/16" in diameter it can be used as a pilot. The key is to grind cutting edges on the inside edges of the reamer:
Then, because the reamer is now being pulled not pushed there needs to be a place to grip the reamer with a tap holder:
I then trim the inside end of the bushing to be flush with the curvature of the carb bore. Then do the same on the other side...