You should be able to cut the thread on the lathe, I'v managed 3/8" BSF when I could not get a tap anywhere in this town, and it was an urgent job, the local engineering firm did'nt think it was possible to do on their machinery, but they neered to get their compressor going again (it was a castelated nut in the valve gear).1 1/2 hrs, nut made, including hex and split pin slots. Ian S C. ps; You could make an adiquate tool from a 1/4" slot drill, or even a twist drill of a similar size, unless you already have a small boring bar. Ian S C