General question; milling slots

[TomG]

(11-19-2017, 11:19 AM)pepi Wrote: While I'm thinking about it, the piece you are milling, is alum. You mention that if not making the demo, you would mill @ 400 rpms, tool 7/8.

 I have a chart, that basically says the same for steel, then is small print it states, alum, cast iron & bronze dived the speed 1/2. ?

Not saying this is correct, cause I always side on the side of experience, so I'm questioning the chart.

Greg

The general rule for rpm is to multiply the cutting speed of the metal being milled by four and then divide by the diameter of the end mill. In the case of mild steel, the cutting speed is 100 surface feet per minute, so 4 X 100 / .875 = 457 rpm. The cutting speed of aluminum is 400-500, so the same formula would result in 1828 to 2288 rpm. There really is no upper limit on aluminum, as long as you can get the chips out of the way fast enough so as not to clog the end mill.

I also have a video on cutting speeds and if you look in the reference section of my website, there is a nifty rpm chart for various metals.

Tom