AccusizeTools - Boring Head R8 Bridgeport Shank, Threaded 1-1/2'' x 18 per Inch, 0355-0108 Boring Head R8 Bridgeport Shank, Threaded 1-1/2'' x 18 per Inch Threaded 1-1/2''-18 per inch Max. Size: 1" Straight Shank For the Boring Head 3'' #0350-0003 & Boring Head 4'' #0350-0004 0355-0108