Downcut or upcut?

1

I am cutting some small shapes out of 3/4 red oak, using 1/8” down cut bit, about .125doc, even step downs. Reading the forums, the down cut works better to keep the pieces in place, but I am having an issue with the bit not cutting all the way through.

1st time I ran the file, the wood was only cut down to about .65”. Checked fusion, generation looked good, so I ran it again, and this time it cut all the way through. Thought maybe the bit slipped up in the collar under pressure, no big deal.

Ran the file again for a new piece, and it did the same thing, didn’t cut all they way after the first run. But after rezeroing (separate question) and re-running, went all the way through.

1f is showing the .77 depth while making the final pass (.75+.02 extra), but clearly the bit is not at that level. Are the shavings that are trapped from the downcut causing the a to bind thinking it’s lower than what it is? This is the only idea I’ve come up with. Should I be using an upcut instead and risking pulling the edges of the pieces up on the final pass?

2

Build up of chips can be a problem.
Have you tried a v bit first to chamfer the top and then run a upcut bit
Just a thought. You still of course must be sure the part cannot move. Could be a challenge depending on how small the part is.

3

Should I be using an upcut instead and risking pulling the edges of the pieces up on the final pass?

You can use the downcut bit for 50% of the cut, then switch to upcut and finish the remaining 50% including cutting through the other side.

This will provide you the benefit of each bit on each side of the piece.

If you wanted to eliminate the bit change, you would need a compression bit.
But compression bits typically leave you will less control of stepdown since you must reach a certain level before entering workpiece in order to achieve the desired effect of the bottom upcut and upper downcut portions.

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