How to Flatten a Slab with a Circular Saw or Router
Watch to see how to build a simple sled that will let you flatten wood slabs with just a circular saw or router! Yes, I know I use the band saw to make a cut in the video, but you could do the same cut with a circular saw or just leave the piece large.. it was purely aesthetic.
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I raided my plywood scrap pile to get all the pieces for this. It’s 23/32” or 3/4” pine plywood. I decided to leave the back wall of the sled tall thinking that add more rigidity because of how wide the sled will be.
To make the ends I mocked up the sled and then transferred the height of the front and back to the end piece and connected the dots before cutting it on the bandsaw. Then I just copied the finished piece onto the second piece and cut it out.
I assembled the whole thing using 1 1/2” #8 wood screws. I used a pilot bit that pre-drills and counter sinks at the same time to make sure the screws wouldn’t blow out the wood. Glue and brad nails would work just as well, but I didn’t want to wait for glue to dry.
For the circular saw to work in this I cut a base that would fit snuggly inside of the sled and marked where the cut out in the sled met the base. I used those marks to help me position the saw on the base because when the blade is lowered it has to fit inside that cut out. Then I used a handful of wood screws to secure it snuggly to the base. I positioned the saw at a slight angle so it will cut a groove instead of a thin kerf with each pass. This will make feeding the saw go slowly, but I think that speed loss will be made up by the fact that you’ll removing quite a bit more material in each pass.
The sled needs some rails to ride on. For that I used some straight 2”x4” cut offs and screwed some feet onto them to make them stable. To make sure the rails are perfectly straight you could run them over the jointer or table saw, but I wanted to show this entire build could be done with just a circular saw and still give good results so I skipped that.
Now time to test it. For testing I just put a heavy slab on my driveway and then wedged it so it wouldn’t rock. It’s a personal judgement based on the slab and tool whether you need to secure the slab to something.
The circular saw worked well. My results were a bit rough, but it would clean up quick with a belt sander, or I could have gotten better results by moving the sled less between each pass. Now I did make this to work with a router as well, so I went ahead and tried that. The router came out a lot cleaner and was faster because the bit takes a much wider cut each pass than the circular saw. But it still needed some belt sanding to smooth it out. I’ll leave a link below to the inexpensive router bit I found on amazon that worked well.
I made this sled to batch out some tables from some wood I collected last year that is dry now. To make these tables I put the sled on my workbench so I could secure the smaller slabs. That worked well and my back was very thankful to not be working on the ground, but it did take me about two weeks to get all of the sawdust cleaned up.