(11-19-2017, 02:50 PM). TomG Wrote:(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
You read my mind in the very last paragraph LOL. Think it is time to buy The Machinist Hand book. I do remember your video, showing the cutting speed and formula. I like to use large mills to cover large areas to keep the tool marks to a min.
Thanks again Tom
Finished the part ....... probably guessed it is the steady bed clamp, to much torque on hold down bolt, broke it in half. My guess is I'm not the first one to do that .
Greg
Magazines have issues, everything else has problems