I picked up a nice Bridgeport No. 2 boring head in great condition. Only problem was it came with an R8 shaft. My Index Mill uses nmtb 30 tool holders. I thought it would be easy to find a new shaft for the bridgeport head but the threading is 1 1/4 x 20, which, it turns out is not common. I had a 3/4 inch nmtb 30 tool holder so I decided to try to turn the R8 shaft down to 3/4 inch. I used a brazed carbide tool and turned it without difficulty.
