I was machining a cast iron component with a 0.25 4 flute end mill at 1200 rpm and 20 ipm and all seemed well, good finish.

I then did a helical circular cut to enlarge a hole and thinks went south in a hurry with the mill becoming red hot and wearing dramatically. I was advancining 50 thou per revolution with this cut.

Any thoughts on what went wrong with this second approach? I was cutting at 50 thou depth at constant z without difficulty.

Wayne

Yeah, The .05 per rev feedrate. That is .0125 per flute. You should have been .012 per rev at the most.

... I was advancining 50 thou per revolution with this cut.

Any thoughts on what went wrong with this second approach? I was cutting at 50 thou depth at constant z without difficulty.

Wayne

50 thou per revolution with a four flute is 12 thou per tooth; much too fast, drop this to around 4 thou per tooth. In addition for machining cast iron with a HSS cutter your rpm is a bit high; 1200 rpm is 78fpm, I would drop this to 50fpm, i.e. 800rpm or so.

Thanks guys, I still have to get my head around feed per tooth.

Wayne