I recently bought a copy of Machinist Toolbox and have been playing around with its feed rate calculator for milling with endmills. According to them they use default chip load values for their feedrate calculator from the Machinery Handbook. If you change between HSS and Carbide for the endmill or even the workpiece material you can see the chip load change in their calculator window as you expect. I realize that precise chip loads are somewhat dependent upon the actual design of the cutter but I'm OK with Machinery Handbook values for my use. What I am confused about, though, is when I change the diameter of the cutter the chip load value doesn't change. When I emailed them and asked about this I was told that the chip load is independent of the cutter diameter. This doesn't sound right to me. Am I missing something? I wouldn't think one would mill with the same chip load for a 1/8" cutter as for a 1" cutter. Running some examples with their calculator for rough cutting 6061-T6 aluminum with a 2 flute HSS endmill:
Inputting .5" dia cutter and 400 FPM into their program gives: .00575" load per flute, 3055 rpm, F=35 ipm, radial doc=.2", axial doc=.425", removal rate=2.99 ci/min, 1.2 hp
Inputting .125" dia cutter and 99 FPM into their program gives: .00575" load per flute, 3025 rpm, F=35 ipm, radial doc=.05", axial doc=.11", removal rate=.185 ci/min, .07hp
Shouldn't the chip load vary inversely with the cutter diameter?