Best cnc bit for plywood, up-down bit, 2 or 3 flutes?

[designer_daddy (Gary W)]

Has anyone used the Amana up-down cut 1/4" bit? Which is better for plywood, 2 or 3 flutes?
Is there another brand you would recommend?

Thanks.

[LiamN (Liam Newcombe)]

It all depends what cuts you’re making, I’ve successfully used the Carbide 201, Yonico up cut / down cut, high helix, low helix and compression bits, rennie tool up cut and compression and a few others on baltic birch ply. Those are an assortment of 2 and 3 flute, I’ve not noticed any real difference between them after setting up the feeds and speeds for the right feed per tooth.

It’s a lot more down to getting the toolpaths, feeds and speeds right so the machine isn’t vibrating, your dust extraction is getting the chips out of the cut so you’re not clogging up and recutting, you’re not plunging too deep etc.

Typically an upcut is going to behave better for your main roughing cuts because it will pull the chips up out of the cut for your extractor to clear. A compression cutter used full depth in shallow stepover to clean up the last 0.5 - 1mm of the edge leaves a super clean edge for me. If you’re pocketing in the wood then a shallow helix downcut can clean up the edges of the pockets.

[LiamN (Liam Newcombe)]

Here’s a few tests of different cutters I did in baltic birch;

Baltic birch Plywood

So, I went and found some offcuts of furniture grade 18mm Baltic Birch Ply and did some experiments with some blunt cutters, sharp cutter and a compression cutter. The TLDR is that, if you use sensible feed rates, a good toolpath strategy and are prepared to do a little manual finishing, you can get away with surprisingly blunt upcut cutters. I found the fastest way to tell if the cutter was still sharp was to carefully and gently run my thumb across (not along) the cutting edge near the top …

[gmack (Gerald Mackelburg)]

@designer_daddy

Is there another brand you would recommend?

I’ve used a Whiteside RU1600 0.125 inch 2 flute upcut endmill at 27000 RPM and 60 IPM to cut Baltic Birch with 0.125" deep passes.