[Project_Hopeless]

I have a DIY CNC router that is speed limited running 5mm lead ball screws. So plenty of torque limited speed. :tired:

My immediate need is to cut plywood up to 3/4", both softwood and hardwood including marine grade.

My router is a 2-1/4HP with a min speed 8000rpm. So from my understanding I'd probably want a 1/4" single flute carbide cutter to maintain a decent chip load.

Is my understanding correct?

Second, I searched Ebay for Onsrud and a lot of single flute cutters come up labeled for aluminum. Are these suitable for plywood and other woods?

[ger21]

How fast can the machine actually cut? At 8,000 rpm, you're fine to use a 2 flute bit.

[Project_Hopeless]

How fast can the machine actually cut? At 8,000 rpm, you're fine to use a 2 flute bit.

Not sure. I hope to power up for the first time this weekend.

Embarrassingly, if my calcs are right, ~50-60 ipm. If I had 1/2 the inductance and twice the lead I'd be 200-300 ipm territory. For the time being I have to make due with what I have.

With that in mind would you still recommend 2-flute cutters?.

[Project_Hopeless]

My understanding is with a compression bit you need a depth of cut that engages the down spiral with the top surface, So for example a 1/4" tool, 3/8- 1/2" (~7-10mm) deep cut.

For Birch plywood, would you recommend using a compression bit on a DIY hobby machine?

[ger21]

Yes, I'd still use a 2 flute bit.Unless you can easily find inexpensive single flute bits for wood. The "O" flute bits for plastic and aluminum will work OK for wood, but they tend to be expensive.

I don't use compression bits on my DIY machine, because I don't really need them. They work best when making one full depth pass. If you make multiple passes, you'll wear out the tip a lot faster.

[Project_Hopeless]

I'm looking for an economical spoil-board surfacing bit/cutter. I came across this one.

https://www.grizzly.com/products/Gri...xoCPaAQAvD_BwE

Can I do better than that bit for similar money? I have a 48x48" table and 2Hp router so I was thinking 2' cutter 1/2" shaft.

[nlancaster]

I use this one.

https://www.amazon.com/Magnate-Surfa...222962&sr=8-15

But that grizzly looks decent, and it is cheap.

[ger21]

Any straight bit will work, and you probably won't find a 2" bit for less than $25.

[Project_Hopeless]

For 3/4” plywood you want to use a 7/8 or 1” long bit correct?

Or does a typical 3/4” spiral up or down cut bit have enough edge for cutting and chip clearing?

[ger21]

Yes, 7/8 or 1".
Since most plywood is undersize in thickness, you can usually get away with a 3/4" bit, but a little longer is better. The flutes on a spiral bit extend beyond the cutting edges, so that's not an issue.