I have a 770 Series 3 and a TC tapping head. I'm trying to tap 6-32 in 1/4" thick 6061 using high-speed mode at 800 RPM with a good HSS spiral flute tap. Yes, I calibrated speed. I'm using conversational in Path Pilot and set the dwell to 0.4s. All seems to go well and the program runs fine, but many threads are fouled when I try to run a screw through. It appears the entry threads get mangled when the TC head pops up slightly coming out of the hole. At least that's the only thing I can guess. I've messed with the dwell to try have no compression or tension when the tap leaves the hole, but I've noticed that the tension is not same on every hole, so I can't find one dwell that never "pops" on exit. Maybe my speed is varying too much because I'm trying to get away without changing the belt to low speed. Obviously, the point of the TC head is that it CAN compress or stretch a bit, so it seems this shouldn't wreck the threads. The other possibility I wonder about is maybe the TC spring is too stiff. It's seems stronger than necessary, but I don't know what normal is. If it were weaker, maybe it wouldn't rip the threads (if that is in fact what's happening). I have to chase all the threads with a hand drill after the job, which kind of negates the point of TC head. I could just as well tap them with the drill. I'm hoping someone has wisdom to impart. Thanks