Splinter/frayed edges on baltic birch plywood

So I made a sign on baltic birch 3/4" and it looks sharp, then I went to make another and I got crazy fraying and splintering on the surface of the baltic birch.
Speed was between 3 and 4 on makita router (20,000rpm)
Full depth of cut was0.1" - 3 passes of 0.03" and 1 final pass at 0.01"
stepover was 48% I believe.
Using 1/8" end mill in pocket and 60" Vbit and both produced tearing/fraying on the surface.
Any helpful suggestions?
Thanks all, look forward to hearing from you.

@MpH Dull bit? Plywood chews bits because of all the glue.

Too fast feed?

Is your mill a down cut or an upcut. You need a down cut for a clear surface.

Hi thanks, its a DC bit from sienci and I tried a new bit also with limited improvement but still have some fairly fuzzy edges, notably mostly in a similar cut direction. I tried a raster cut just to explore, still fuzzy.
I am going slow the router down to 2-3, 16,000rpm, see what that does.
How long is a bit generally good for in Baltic Birch?
Thanks for responding.

@MpH What’s your feed rate, Mike?

Hi thanks again, its 800mm/min

@MpH That’s really slow for that router speed. I wouldn’t have thought it would cause chip out. I would have thought that, if anyting, you’d be getting burning. Looking at a chip load calculator, at 16000 in plywood, your ideal speed would be about 4 times that. That said, I would try to slow down the router to 12000 and set your feed to 2500 and see what happens. No guarantees, though. If it is good plywood, you should be able to get good clean cuts with a sharp bit.

I really can’t say how long a bit is good for. I likely use them too long, because I’m cheap. When the quality of my cuts drops off, I toss the bit and replace it with a new one. On plywood, that doesn’t take too many jobs. All the glue just beats bits up.

Thanks for the insight, Its really puzzling to me, I’m gonna keep tinkering with the feeds n speeds, but not 1 burn mark so ya…
Also the ply is bb rated baltic birch, pretty top notch as far as ply goes, no gaps or cheap fillers between plys.
Thanks anyway.

I will try to plug those numbers in and see if there is an improvement.
I will post results tomorrow.


This was my latest attempt
12000rpm
2500 feed just as fuzzy as the first.

@MpH No offence, Mike, but are you sure that is a downcut bit. Those cuts sure look like upcut.

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none taken. Great question! Ill confirm. I ordered them thinking i was getting DC, never really confirmed.

Its always the oversights inst it.
I brushed the upcut factor away earlier today without doing what you just helped me do (confirm tools)
These are the 3 I got in the starter kit and I assumed DC. Shame on me and thanks to you for guidance.
Im ordering my DC now.
Thank you sir.

@MpH You’re very welcome, Mike. It’s the picture you posted that did it. You may already by aware of this, but never use a downcut bit to drill holes, unless of course, the holes are much bigger than the bit. So, drilling a 1/4" hole with a 1/8" DC is fine. Drilling a 1/8" hole with a 1/8" DC or a 1/4" hole with a 1/4" DC is bad news. There is nowhere for the chips/sawdust to go. So it gets packed down. And it gets very hot as a result. I have the scorched spoil board holes to prove it.

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Thanks for this thread. Was super helpful. I had the same problem with my birch plywood making some Montessori math tiles for the kids.

@Twintails Welcome to the group, Twintails. You’ll find that this is very helpful group.