HAVING PROBLEMS WITH 1/4-20UNC TAP!

[CASIO]

Hy guys!

I'm new here, and i'm in touch with you asking for some help!

I've to machine a lot of 1/4-20unc threads, and i'm having a lot of problems to.

I'm using a 5,2mm solid carbide to do the hole, and using a 1/4-20unc HSS-E tap to do the thread, with 9 Meters per Minute speed, floating tapper. But the tap is enlarging the hole and recutting the thread. I've made a lot of tests, but I couldn't discover why it's happening. Can somebody help me??

Thanks a lot!

[underthetire]

What rpm? Can you program in feed per rev mode?

[holbieone]

What type of tap holder are you using, sounds like the tap is dragging on its way out

[jvangelder]

whats the material?

9 meters a min is around 350ipm.. around 7,000rpm, id try slowing it down?

[uli12us]

I know your problem, I had this only with blindhole taps. If you use a throughhole tap, it should be gone. If this isn't possible you should better use a forming tap. In this case, your hole must be bigger, the diametre should be in the middle of inner and outer diametre + 1-2/10mm.

[John Wheeler]

I thinking you are pulling out so fast that your maxing out the spring in the tapper and basically pulling the tap out of the hole.