My company just received a new sl30. Our "head machinist" who's experience is extremely limited in any type of lathe work insists that we run this new machine extremely slow. My experience is also limited and its been quite a few years since I ran lathes. Most work I did was toolmaking turning hardened tool steels and the like. My question is we are running some simple locator pins. Stock is .750" low carbon steel 4" long. Finished part is. 737 dia with a 1.5" long taper down to .25. I recommended a speed of 1200 rpm a rough cut of .004 and a finish cut of .0025. He has kept the feeds as is but has slowed the spindle to 300-400 rpm. Am I off base with my calculations on this? Any guidance would be much appreciated. 8 minutes to run one of these seem absolutely ridiculous. I could almost do it as fast on a manual lathe.
I assume you have the 3400 rpm spindle. I will also assume you are using modern coated carbide inserts. If this is all true then prepare to be blown away. You should be running a surface footage of at least 750 so you'll be running that spindle wide open. The roughing feed rate can go as high as .025 ipr without any problems and D.O.C. can go as high as .2 ( .4 off the od ). With the material being so small in od I would recommend skipping the roughing tool and going straight to the finishing tool. Ours is a 55 deg. and I run a max doc of .1 and max feed rate of .009. For fine finishes I slow that down to .003 ipr take .02 off the od.