03-11-2009, 06:35 PM
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| | | Join Date: Jul 2005 Location: Canada
Posts: 11,562
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That is a 'smoking fast' feed rate for that rpm.
There is a relationship between rpm, number of cutting edges and feed rate: Most cutters whether they are HSS or carbide are strong enough to take a cut per tooth of something like 0.5% to 1.5% of the cutter diameter provided the depth of cut is not more than about 60% of the cutter diameter if the cutter is working across its full width. Using a 1/4" cutter this 0.00125" to 0.00375" per tooth per revolution; call it 0.001 to 0.004, or 1 to 4 thou, per revolution of the cutter.
The feed rate therefore is the cut per tooth multiplied by the number of teeth and the revolutions per minute: a 1/4" two flute cutter running at 3500rpm can run at 28 inches per minute feed and a four flute at double this.
Obviously the 150 ipm you mention is a too fast. With a shallow depth of cut or running down the side of a part it possibly could work but the surface finish would not be very good.
There are a lot of other things to consider: Lubrication or coolant is almost essential when the conditions I describe are used. With a four flute cutter it is possible there will not be enought clearance in the flutes for the heavier cut and the flutes will load up and break the cutter. The machine has to be rigid enough to prevent chatter and the motor powerful enough to drive the cutter. With a small machine these things are sometimes the limiting factor.
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