its not 100% critical I'm making another part that this will slide into, I was wondering about getting a 4 jaw chuck for my lathe and doing exactly that but I drew it up and it just didn't look nice at all so left that idea. I had also considered trying to find some 8 sided hex. bar but that doesn't seam to be easily available. I really must get on the case of building a better cnc to do this sort of work although it looks like that will now have to include a 4th axis!