Hi

I am trying to tap some M2 blind holes 6mm deep into 6082T6 alli. I have tried a tap at the correct spindle speed but the taps consistantly break after doing 3 or 4 holes. So I switch to thread forming, the recommended speed for the thread former is 3000rpm and this broke in the first hole. I am now having a new one delivered, the manufacturers recommend 6000rpm, I will try this tomorrow.
My gut feel is that these spindle speeds are very high (this is ridgid tapping) I am confident that the machine is up to the job as it's only 2 years old but it seems to me that when it bottoms out and reverses direction 6000rmp is just too fast. The hole I have drilled is 1.8mm and is 7mm deep, is this deep enough or do I go to 8mm (can't go anymore than this).
I have done many successful tapping cycles before be never as small as M2.
Any tips or advice would be greatly appreciated.
Thanks
Ishy