I’m a little confused about the new 8mm endmills (211E, 213E, 214E). Why is the cut depth for an 8mm endmill in softwood set at 1.5mm, when similar 1/4" bits from Amana Tool have a cut depth in softwood of 6mm (and work perfectly well at that DOC)? The only compression bit I have right now is the #214E and I was going to use it for the first time to do a profile cut in some 3/4" birch ply that I need a clean edge on both faces. 7 passes? Really? I’m still relatively new to CNC, less than a year of experience and tend to follow the mfgs suggested feeds and speeds for bits, especially ones I haven’t used before – but this seems ridiculously conservative.
Check out this discussion.
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Thanks, Ed. I’d pretty much worked this out on my own but that discussion made me confident I wasn’t off base. The bottom line is that you need to know the transition height of a compression bit (the height at which the upcut changes to downcut) and your initial plunge needs to be a tad deeper than that height. I learned this the hard way trying to get a clean top-and-bottom profile cut on some birch ply. I didn’t plunge deep enough on my first pass and the upcut flutes produced significant tear-out on the top veneer. Fortunately I was working in scrap :-). My second try plunged below the transition height of the bit and it looked great on both sides of the ply.
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