How fast should the mill spindle spin?
Calculate mill spindle speed using the following formula:
(CS ) * 4 D
Speed is the calculated spindle speed inrevolutions per minute (rpm). CS is the cutting speed of the material, a property that you can find in reference books. It is measured in surface feet per minute (sfpm). Our shop uses the following values:500 plastic 300 aluminum 200 brass 100 mild steel 50 stainless steel
D is the diameter of the tool in inches. Example: If you were using a 3/8”-diameter endmill on mild steel, you would performthe following calculation Speed =
(100 sfpm) * 4 = 1067 RPM 0.375"
Note that when using plastic or very small endmills, you may calculate speeds far higher than our machines can reach. Use thehighest speed available and reduce your feed rate accordingly.
REMEMBER, this formula is only a guideline for selecting a speed. Always use common sense, pay close attention to your work, and adjustyour settings to the situation. If you have a question, always ask a TA.
What is a good mill feed rate?
Calculate mill feed rate using the following formula:
Feed = (ChipLoad ) * (n) * ( Speed )Feed is the calculated feed rate in inches per minute (ipm). ChipLoad is the amount of material that each flute will remove on each revolution. Each material/operation has a suggested value, which youcan find in reference books. It is measured in inches, sometimes written inches per tooth (ipt). Our shop uses the following typical values: 0.005” for roughing 0.001” to 0.002” for finishing n isthe number of flutes on the tool. Speed is the spindle speed in revolutions per minute (rpm).
Example: If you were doing a roughing pass with a four-fluted endmill turning at 1000 rpm, you wouldperform the following calculation
Feed = (0.005" ) * (4) * (1000rpm) = 20ipm
REMEMBER, this formula is only a guideline for selecting a feed rate. Always use common sense, pay close attention to your...