Spoil board/slab flattening Bit Question

Re: Spoil board/slab flattening Bit Question

Dick Coers

As long as you don't plunge cut, and bit will cut. If you take light cuts, a spoil board cutter will cover ground faster. If you want to not have a dedicated bit, I'd go with a Freud large diameter pattern bit with the bearing on top. I have an 1 1/4" diameter that works exponentially better on pattern work because of the time speed and rigidity. Would make a fine planing cutter too.

Pardon my slow response....

Barry Irby

I have been milling over you answer (See what I did there?) and waiting for additional suggestions.

I like you answer with a couple of caveats....I am generally looking for a dedicated bit. I bought a router carrier (?) that looks' like the circular saw carrier mounted on the plywood cutter you see at the Borg. It's an aluminum frame that will ride on the pipes and raise and lower the router. I paid a dollar for it. I got a big honking Porter Cable router at the same sale for two bucks. Looks rough but works well. So I am cobbling together a flattening system and will most likely leave the bit in it long term.

I like the idea of a spoil board bit with replaceable cutters. The problem I envision with the bit you suggest is that essentially ALL of the catting will be done by the bottom 1/8" or maybe 1/4" of the bit. I have about three dozen red oak slabs I could flatten. So wearing a 1/4" of the bit out is a possibility.

OTOH, I have been wanting a pattern bit as you describe for the exact reasons you mention. And, if the cutting depth is say 1 1/4" the remaining undamaged 1" would be sufficient to do 99% of my pattern routing. So, I could buy such a bit and try out my contraption and if I like it could then buy a spoil board bit. If I don't like flattening the slabs or my contraption, I would have an excellent bit left over. Sometimes I overthink things.

Complicating things further, the guy that milled the slabs for me has a CNC and will flatten the slabs for several hundred bucks each. He also has a kiln. These slabs have been air drying over a year. I COULD take one or two to him, kiln dry them, and flatten them and take them home. I'm guessing about $500. Hmmm?

These slabs are big enough to make single board tables.

Re: Pardon my slow response....

David Yoho

I didn't know what a spoil board was until doing a little research. After reading your first post I wondered why not use a jointer and planer or, for that matter, hand planes. After reading your second post I see these boards are probably wider than your machine's capacity. While this could still be accomplished by hand, if you're like me and don't posses that skill, machining would be my choice.

So, if you're able to cobble up something with your big router I would think a bit like the Amana Tool RC-2250 with a 1/2" shank would work well as long as you're not plunge cutting. Plus it's a lot cheaper than paying the guy with the CNC to do it.

Re: Pardon my slow response....

Barry Irby

I have very limited knowledge of the CNC world but I gather they call the sheet of MDF that form the surface of the table a "spoil" board, because they spoil it while working on it. The machine cuts into it and the operator screws work down to it. So apparently they install one of these bits and shave away enough of the surface to refresh it. I hope they have excellent dust collection because the dust from MDF is nasty and copious.

I have a few hand planes and am making friends with them, but would not try to surface plane a piece of MDF. Or a giant piece of oak.

My reading since I posted indicates they expect you to take .05" deep passes with the surfacing bits. Less than a 1/16" and far less than the 1/8 or 1/4" I was contemplating. Hmmm.

Also some of the bits like the Amana you suggested indicate they should be run at over 16000 rpm and my router is a fixed speed one and runs at 24000. I need to find out what the issue is. I would not want the thing to throw one of those cutters. I would have to operate it from about five hundred years away. But it's possible there is some other issue such as poor cuts or vibration. Need to do more research.

I looked up the bit you suggested on Amazon and one the same page was a smaller version, 1 1/2" rather than 2", maybe that will work. Thanks, off to do more research. Maybe I need a router speed controller.

Re: Pardon my slow response....

William Duffield

I haven't tried it myself, but I've seen lots of articles and videos of people successfully flattening large slabs with a router in a plywood C-beam between rails. Personally, while I would find that kind of work extremely boring, that is a problem the CNC machine doesn't have.

I figure you could buy a lot of router bits for the price of a flattening by the guy with the CNC. I don't know how far away he is from your slabs, but you need to take into account your transportation time and costs, too.

if you are concerned about wear and tear on router bits and your $2 router, maybe rough removal of a lot of the oak with a circular saw running on a similar jig would be cost effective? That would of course depend on how much you need to reduce the thickness of your slabs.