Gene Heskett wrote: > Ouch! And no wonder I'm getting snow flakes. Or in steel, very sharp > needles I'm always picking out of my fingers. Yeah, I know about those! But, those numbers were for mild tool steel. For aluminum, the strategy is a bit different. > But this stuff is alu, the 2" > wide, 1/8" thick bar stock they sell at Tractor Supply. Petty soft, gummy > stuff too, but cuts to length on the chop saw nicely, 12" saw. That width > limits me to 13 teeth if I want full height teeth on all of them. > The chop saw will cut anything. Gummy aluminum, you DO NOT want! Does it have a "striped" appearance? Most likey something like extruded 6061. You CAn machine it, I've done a lot, but you have to take light cuts and keep the tool moving along. If it heats up, even a LITTLE, you are in trouble. > And I was running at 1.5, and about .033" deep with an already dull bit when > I broke it the second time. Alu was piling up in front of the mill so I knew > it was a matter of time, something it wasn't doing when the mill was fresher. > > By then, you are in deep doo-doo. Are you conventional milling? That is where the material is fed into the cutter opposing the direction the cutting teeth move? This is the worst method for surface finish and tool wear. If your machine can handle it, you want to do most of your work in the "climb milling" direction. This is where the cutting teeth move in the same direction as the material feed. The advantage is the teeth bite directly into the uncut material, starting with a full chip thickness. In conventional milling, the tooth slides aling the already-cut surface until enoguh pressure is developed to force it under the material surface, then the thickness of the chip increases. This sliding causes much increased flute wear and welding of re-cut chips to the surface. If your machine has a lot of backlash, then the direction of cutting forces can cause the work to be pulled into the cutter, breaking bits. But, if the friction exceeds the cutting force, or the backlash can be kept down, you will get better surfaces and longer tool life. > I only had maybe 1/4" of it in the collet at the time, and I expected to see > alu piled up in the flutes, but amazingly, it was clean, no stuck chips. > Just apparently dulled by all the alox it had cut already. These are TiN > coated mills, $5 ea at Hemly, just across the Ohio river from me. > I wouldn't waste money on the TiN coating for aluminum.
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