Start by assuming it's Imperial. The gearbox will tell you the feed in inches per rev. Multiply inches per rev by spindle speed and you get inches per minute. Divide by 39.37 (40 would be near enough) to get metres per minute. Actually inches per rev is more sensible. A reasonable starter for10 is 0.004 in/rev, or 0.1 mm/rev in metric. Your quoted figures must be mm per min, not metres per min, and give 80/500 = 0.16 mm/rev, just over 0.006"/rev which is a bit heavier cut, but still sensible

I don't know what mpm is, but 80m/min is never going to be a sensible feedrate on a lathe, or even a mill for that matter.

My advice would be to ignore information online, a lot of it is worthless and/or just plain wrong. Tell us what you want to do (material/diameter as a minimum) and I expect we can come up with some sensible spindle speeds and feeds. I would think that the gearbox on your lathe will list distance per rev in some positions, as well as tpi.

Andrew

It sounds like you have been looking a milling feed rates as they are given in ipm (inch per min)

What is the diameter of your steel, What grade would help, what tool ar eyou using HSS or Carbide

So for HSS tools a cutting speed at the surface of the metal would be in the region of 30m/min divide this by the circumference of the work ( 0.02m x 3.142) which gives 30/0.063 = 476rpm so your speed was about right had you been using HSS but was too slow for carbide that could easily take 2 to 3 times that speed.

As for feeds I tend to use quite a conservative feed and for finishing would be using about 0.06mm per rev or 0.0025" per rev and double that for roughing out. I would use the same feeds for either HSS or Carbide. Andrew would tend to go a bit more but he has a heavier duty lathe than me.

You need to make sure you use the feed lever on your lathe not the thread cutting lever as the carriage will tend to move too fast if you do

Edited By JasonB on 23/08/2020 20:56:06

Of course it depends upon the exact type of steel, but as a starter, with insert tooling, I'd be running at 1200rpm and 0.1mm/rev for finishing and 0.2mm/rev roughing.

Andrew

Postscript: My lathe doesn't run fast enough to use recommended surface speeds on 20mm diameter aluminium. I might up the speed to 1700rpm but keep the same feeds. I would change the insert to a CCGT aluminium specific one.

Edited By Andrew Johnston on 23/08/2020 21:35:42