I am making an ER40 chuck for my lathe. It requires internal threads to be cut for the spindle threads and also for the nut (I am going to make my own nut, or at least try). This is a wonderful learning experience for me and so far I have succeeded in my efforts (haven’t started the nut yet). Both internal threads call for a relief cut behind the threads and the drawing I am following shows this cut with sharp corners. What is the proper way to do this? For the main body of the collet, behind the spindle thread location, I ground a piece of HSS with square corners on both sides (i.e. rectangular looking down from the top) with relief angles. I then plunged into the inside side wall using a boring bar to hold the HSS cutter. It worked but it chattered somewhat and I couldn’t help thinking maybe there is a better way to do this?