Quick ? on Compression bits

Hey all,

I read somewhere that when using a compression bit that you need to have your first pass deep enough for the downcut to enact. Which kinda doesn’t make sense considering rule of thumb is to not go deeper than half diameter of the bit. This particular Whiteside compression bit i have it looks like the down cut starts at a 1/4". So my first pass should be 1/4" obviously… but my bit is also 1/4", so it scares me to even try. I’m assuming its gonna work fine with the proper feed rate. Just wanna hear some of your success/fail stories.

Also with a compression bit, should I not do ramp plunges? I could see that causing some chipping on the ply as it gets to it’s depth.


If you’re using software that can handle generating the toolpaths for it (or willing to “trick” software that doesn’t), your best bet would be to use the compression but for a full depth finishing pass. Basically, run the profile leaving some stock on the edge of the part. Come by with the compression bit to finish it up, cutting from the side.
I hope that makes sense.

I run a 1/ 8 compression bit at 1/8 doc with no trouble. 1/4 that deep might be a different animal, but it shouldnt hurt anything to give it a go.

Keep in mind you may find a depth less than .25 that still gives you desirable results as there’s usually overlap between up and downcut sections of the compression bit.

I too have contemplated ramping and think I will be doing a lead in ramp so that the first plunge doesn’t create any rip out before it gets to downcut depth.

1 Like

I have the exact same question as ColeChapman except that in the case of my 1/4” compression bit, it starts at 5/16” so I would need a DOC slightly greater than the bit diameter. I am not sure how much overlap I have between the upcut and downcut portions. Also related… is there a way in Easel to have a different DOC on the first pass and subsequent passes?

1 Like

Its best to use a pass depth equal or greater than double the upcut portion, however ive run many times with just a tiny bit into the downcut portion and it worked out alright, a very thin veneered plywood could still chipout with this approach though, thats why the deeper method is better.

The simple answer is No.

But kind of, the carve would have to be done manually with multiple carve setups, however IF the cnc can handle that first pass at the required depth per pass, I would just let it do the passes at that deeper depth per pass instead of one pass deep and the rest more shallow.