Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Bherr on May 24, 2006, 07:55:12 AM

Hey guys, Finally got all my problems with the shopmaster and BobCad software corrected and now ready to start milling. I checked in my machinists ready reference book for the proper feed and speed rates for milling aluminum. I'm using a .375 flat milling bit and want to do some surfacing, taking only .0625 depth of cuts. In the bobCad they have F20 for feed rate and F15 for plunge rate. Not quite sure what that means???? the refernece book say for 1/4 bit and 1/4 cut the feed rate should be .005.020 and the speed at 250. that seems very slow for turning speed. Anyone out there help me.
8142431673 or reply here.
thanks
Ben

There is a Feed and Speed Calc in Mach3 under the wizards. The 250 is FPM (Feet Per Min) and the .005.002 is the chip load per tooth. use this formula 3.82 * FPM/Dia = RPM 3.82*250/.25 = 3820 RPM and if the cutter had 2 cutting tips the feed would be CuttingTips*RPM*Feedpertooth = IPM (Feed rate) 2*3820*.0025 = 19.1IPM
How is that :)
Brian

Hi Brian,
What exactly does the 3.82 represent? I see that it's used as RPM. But is it a constant that you use always? Or is it specific in this case given the other known factors?
Just curious as I've never known the formula.
Thanks

3.82 is (12/PI) it is where the Feet in Feet per min get converted to inches and PI is needed to get the circumference.
Hope that is what you were looking for...

yeah, cool! thanks.