I recently made my first foray into what might be called HSM. My little CNC mill has a KaVo spindle which can be run anywhere between 5K and 50K. Cutter was a 1/8", 4-flute uncoated microcarbide EM, new.
The material machined was fairly hard sheet carbon steel, 0.062" thick, unknown Rc but probably slightly harder than "spring" temper. The actual objects are Uzi submachine gun magazines which I am modifying to fit another firearm. The cuts consist of a simple rectangular clearance cut of 0.600" X 0.500" through the sheet steel, and a magazine catch slot of slightly smaller dimensions.
Here's what happened. I imported a DXF of the cuts and specified 0.015" Z step distance, 6 ipm feed. The best cutting action I obtained was at 12K RPM, but even then the cutter rapidly dulled. At slower RPM, around 8K, the cutter snapped. At higher RPM, around 15K, the chips came off sparking, it was ugly. In all cases, the cutter rapidly dulled and eventually broke. Coolant: I don't have flood yet; I was using hand applied tapmatic gold for lube. I broke or wore out 2 end mills to make only 12 cuts.
Am I WAY off here with speeds/feeds? Am I simply expecting too much from uncoated cutters through some fairly hard steel? Any thoughts and comments are really appreciated. This is new ground for me. I have experience with slower, manual machining.
Thanks fellas!:rainfro:
Oh yes, can anyone recommend software to determine speeds and feeds for this type of machining? I'm going to use primarily 1/8" and 3/16" carbide ball and normal end mills in a variety of materials with this spindle.