This is not a BobCad problem, but I know there are some really smart guys on here and I really don't want to hear all of the BS on the General Forum. I have been having a problem machine wrench flats on some round parts. I have the same problem on my cnc mill and the manual mill. First off I am using two square collet blocks, not imported ones. I am holding the rod on each side of the area that I want to mill the flat on. The problem I have is that the flats are not the same depths. One side will be deeper than the other. I am setting the blocks on parallels, machining in the Y axis. I am careful to place the blocks on the parallels and I even tap them down before tightening the vise. Both blocks are clamped in one vise, although I had the same exact problem on a longer part where the blocks were held in separate vises. The only thing I can think of is the blocks may not be parallel?? I'm pretty sure that it's not operator error, but you never know! I'll check the runout of the part, but I don't think there is enough to be causing this problem. I did check my Z height when I previously experienced this problem, if I remember correctly it was about 0.003" - 0.005". I haven't measured what my flats are but you can easily see that the flats aren't the same depth. Any thoughts??