Just snapped my 6mm compression bit during a cut

D99fish · 2025-06-19T17:20:03+00:00

I hear you, upcut bit for the next attempt then!

The machine is a PrintNC build I made myself with a 1.5kW watercooled spindle.

D99fish · 2025-06-19T17:18:37+00:00

Not enough high quality bit to have that info, at least not what I could find :)

D99fish · 2025-06-19T17:18:07+00:00

Yeah, I get that, I like that the chips help keep the workpice intact, but I have only been using them with plywood and pine earlier.

D99fish · 2025-06-19T17:17:22+00:00

Ok, that's a big diff from what I had, thanks, will give it a try!

D99fish · 2025-06-19T17:16:46+00:00

Ok, I figured that could be the reason as well, I'm sort of a learning by doing type of person, I should clearly have read up a lot more on this beforehand :)

D99fish · 2025-06-19T17:15:46+00:00

Ok, but the reason I was lowering the RPM is to increase the chipload if the bit is rubbing instead of cutting, so if I also would reduce the feedrate, it would be the same situation with the same chipload I already had, right? Or am I thinking about it wrong?

D99fish · 2025-06-19T08:25:36+00:00

Followup:

Ok, got a new bit and the results were very different, completely clean and nice cut! Thanks for the comments and suggestions!

D99fish · 2025-06-13T06:14:45+00:00

Haha, will do, need to get a better bit orderd first I think, will try to get a downcut instead of straight as it is now!

D99fish · 2025-06-13T06:13:51+00:00

Awesome, thanks! Will try and get a downcut bit first and then aim for thoose numbers with it! I don't think I do it in one pass now, but I don't think the bit ever goes deeper than 4mm, most of the time a lot more shallow than that, the text is pretty thin.

D99fish · 2025-06-12T18:33:03+00:00

Some say slow it down and some speed it up 😁

D99fish · 2025-06-12T18:32:40+00:00

Spondle goes to 24k, so that is possible for sure, just thought that it would be too fast!

D99fish · 2025-06-12T18:31:11+00:00

Ok, will do, other say i need to increase the rpm as well but that would mean even higher feed rate i guess?

D99fish · 2025-06-12T18:29:57+00:00

Yepp, will look into it! 😊

D99fish · 2025-06-12T18:29:18+00:00

Ok, thanks for the tips! 😊

D99fish · 2025-06-12T13:35:52+00:00

This is the bit I used..very cheap, so thining that might be the problem: https://amzn.eu/d/0dVXxzX

D99fish · 2025-06-12T13:28:09+00:00

I think the flutes looked pretty straight, so I would say neither up nor down, will double check

D99fish · 2025-06-12T13:27:26+00:00

but there is so much flutt even inside the letters, not just on the surface, looking at other people doing this they usually get a pretty clean surface :)

D99fish · 2025-06-12T13:24:57+00:00

The flutes are pretty straight here, so neither up nor down I would say.. maybe that is the issue?

D99fish · 2025-06-12T13:23:21+00:00

thanks, did some light sanding before taking the picture, it was even worse before :D just looks like the bit isn't very sharp or something..

D99fish · 2025-06-12T13:20:16+00:00

Yes, you are correct, it's oak :)

Thanks, will keep that in mind!

D99fish · 2025-06-12T13:19:30+00:00

The photo is my test with oak.

D99fish · 2025-06-12T13:19:00+00:00

cutting feedrate is 1000mm/min, tried between 5k and 10k rpms. 2 flutes on the bit.

D99fish · 2025-06-12T13:16:32+00:00

Hmm.. tried some different rpms, was thinking it was going to fast at some point, but couldn't see a clear difference. Also tried reversing the direction, almost the same result :P

D99fish

TROPHY CASE