I'm making cable railing stair balusters again. 20 balusters (posts) each with 8 holes drilled at approximately a 36° angle in particular. On each of top and bottom, so that makes 16x20 = 320 holes. I bought a 5/16" solid carbide end mill, US made, and I've been running it at 1100 rpm dry into .120" wall mild steel tube. I'm getting just a little chatter at the beginning & end of the plunge. The end mill is double-ended, and I found I got through both ends, barely, in drilling these 320 holes.
Flood coolant is out of the question here because I'm not set up for it and can't handle the mess.
I've never worked with solid carbide end mills before. Should I have expected more than 160 holes per end, or is that about right?
Grant