Tom wrote:
Those are tapered walls. The contours for those pockets are about 50 thou inset at the bottom of the pocket, so the walls are that much thicker down there. It might be worth investigating using a 3/8 endmill with a 1/16" radius end. That would give some gradation to each Z level step, plus the bottom cut would have the full radiused corners.
Kenneth Lerman wrote: > Get a tapered end mill.One thing to keep in mind when considering the tapered end mill idea is chatter.
The existing stepped design limits the depth of cut (width of cutting edge engaged) to the height of one step. If you use a tapered end mill, the cutting edge will be engaged in the cut over its full length. You are much more likely to get chatter in that case. A high helix cutter will help, as will ensuring that the finish cut isn't too deep.
Another chatter risk is cutting inside radii with a cutter that is the same as (or very close to) the finished radius. If the cutter radius is close to the part radius, then the path of the tool centerline has a sharp or nearly sharp corner. Just before the tool reaches that corner, the amount of tool perimeter engaged in the cut increases dramatically. (Hard to explain in words - see the attached sketch. The heavy red line is the portion of the tool perimeter that is cutting.) The result can easily be chatter and a crappy surface finish.
If you decide to use a tapered end mill for the finishing cuts, keep both of these issues in mind, and take some test cuts. It would be a shame to have the very last cuts in the part start chattering and make a mess of things.
I'm sure both of these issues are old-hat to the experienced machinists here, but I learned them both the hard way - hopefully this will spare someone else the same experience.
Regards, John Kasunich
inside-corner.pdf
Description: Adobe PDF document
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