[KENWILD1]

I have a Haas vert. mill with rigid tapping. We do a lot of tapping with this machine from 4-40 to 1/2-13. We mostly use the 4" ext. taps from Kenametal which are spiral point. I want to push the machine to the max and also the tap. I just don't know where to start. with speed. I have been running a 1/4-20 at 1000rpm and a feed of 50 ipm. any suggestions?

[eaglemike]

What coolant/tapping fluid are you using? Blind holes, or through? What sort of tap holder?
I use a floating holder, and often tap metric stuff a little over 1500 rpm, with nary a problem. Likely could go faster..... I also like to use forming taps in aluminum, especially blind holes.