01-15-2013, 12:11 PM
Ed,
I may get shot out of the water for these comments (with all these armed ships passing ), the chips coming off your cutter are probably the ideal but when I'm turning 4140 the cuttings are long strings or curls. When I get them I get a good surface finish. A heavy cut often yields the bet surface finish, but on your long slender part you may be flexing the stock and getting the tearing action, usually this shows as a harmonic though. The specs for these inserts are often for industrial cnc machines cutting robust parts, not applicable to our lighter equipment and smaller parts. I'd try a lighter cut, lower feed rate and maybe a little faster, but I rarely turn much over 500 or 600 rpm.
My old Colchester slips the belt if taking much of a cut at 1000 rpm so the next speed down at 500 gets most of the use. The big lathe's four jaw is only rated for about 600 rpm, (would have to check)
I may get shot out of the water for these comments (with all these armed ships passing ), the chips coming off your cutter are probably the ideal but when I'm turning 4140 the cuttings are long strings or curls. When I get them I get a good surface finish. A heavy cut often yields the bet surface finish, but on your long slender part you may be flexing the stock and getting the tearing action, usually this shows as a harmonic though. The specs for these inserts are often for industrial cnc machines cutting robust parts, not applicable to our lighter equipment and smaller parts. I'd try a lighter cut, lower feed rate and maybe a little faster, but I rarely turn much over 500 or 600 rpm.
My old Colchester slips the belt if taking much of a cut at 1000 rpm so the next speed down at 500 gets most of the use. The big lathe's four jaw is only rated for about 600 rpm, (would have to check)
Free advice is worth exactly what you payed for it.
Greg
Greg