Fablab Speed and Feeds Calculator

1) Tool Geometry

Tool Diameter = (inches) Details
Number of Flutes = (integer) Details

2) Processing Parameters (see tables below)

Surface Speed = (feet/min) Details
Chip Load = (inches) Details

3)      

Spindle Speed output (rpm) Details
XY Feed Rate output (inches/min) Details
Plunge (Z Feed) Rate output (inches/min) Details
Stepover output (inches) Details
Stepdown output (inches) Details


Generic Surface Speed Reference

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Material Surface speed Comments
MDF 650 ft/minMedium Density Fiberboard - Consider a different material if strength/weight is important. Powerful dust collection is a must, for safety.
OSB 650 ft/min Oriented Strand Board - Often the most economical material to make strength/weight and stiffness/weight dependent things from, like furniture.
Wax 200 ft/min Use this for prototyping a complex machining process or to make moulds for casting.
HDPE 450 ft/min Softer plastic, good for prototyping or for parts that can/should be very flexible. Consider a stiffer material if you need the part to hold a thread.
Delrin/acetal 375 ft/min Good all round engineering plastic, just a bit more expensive.
Acrylic 500 ft/min Quite brittle, need to be more careful about cutting (use small chipload [0.002] and stepdown [0.010]), cheaper material. Water based coolant works well; if not using coolant then max surface speed is 125 ft/min.
Aluminium 600 ft/min Alcohol based coolant works well; if not using coolant, then max surface speed is 200 ft/min.
Steel 200 ft/min Cutting generates a lot of heat, making oil based coolant preferable. Many machining spindles require 2000 rpm or more, to provide adequate cutting torque, which means that you have to use relatively small diameter end mills in order to end up with surface speeds this low. If not using coolant, then max surface speed is 50 ft/min.
Insulation foam 1000 ft/min Good for large moulds and as core for wings.

Chip load

Chip loads are provided as ranges. In order to extend the life of your tool, use the lower value in the range. If need to get your job done quickly then you can a higher chipload within the specified range.

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Material Tool diameter Chip load Material Tool diameter Chip load
MDF 1/8"
1/4"
3/8"
1/2" & up		.004" - .007"
.013" - .016"
.020" - .023"
.025" - .027"		 OSB 1/8"
1/4"
3/8"
1/2" & up		 .004"-.006"
.011" - .013"
.017" - .020"
.021" - .023"
Wax 1/8"
1/4"
3/8"
1/2" & up		 .0089" - .005"
.010" - .015"
.015" - .020"
.025" - .033"		 HDPE 1/8"
1/4"
3/8"
1/2" & up		 .003" - .006"
.007" - .010"
.010" - .012"
.012" - .016"
Delrin/acetal 1/8"
1/4"
3/8"
1/2" & up		 .002" - .004"
.006" - .009
.008" - .010"
.010" - .012"		 Acrylic 1/8"
1/4"
3/8"
1/2" & up		 .003" - .005"
.008" - .010
.010" - .012"
.012" - .015"
Aluminium 1/8"
1/4"
3/8"
1/2" & up		 .003" - .004"
.005" - .007"
.006" - .008"
.008" - .010"		 Steel 1/8"
1/4"
3/8"
1/2" & up		 .0004" - .0008"
.0008" - .001"
.0012" - .0015"
.0015" - .0025"
Insulation foam 1/8"
1/4"
3/8"
1/2" & up		 .004"-.006"
.011" - .013"
.017" - .020"
.021" - .023"

Spindle speed

Spindle speed = ${Surface~Speed~(ft/min) \over \pi * \frac{1}{12} * Tool~Diameter~(inches)}$ =  
Surface speed
$\pi * \frac{1}{12} *$ Tool Diameter
  =   Answer rpm

Feed rate

Feed Rate = Spindle Speed (RPM) * Number of Flutes * Chip Load (inches) = Spindle Speed * Number of flutes * Chip Load = Answer inches/min

Plunge rate

Use a plunge rate of 50% or less of the feed rate. So for a feed rate of ... ft/min, use a plunge rate of ... ft/min or less.

Plunge depth and stepover

Based on a tool diameter of ...", use a stepover of ..." or less.