I just made a sign for my mom out of a 3/4-inch x 8-inch board of cedar. When I placed it on my frame, there was a very slight bow to it (bowed outward from the frame). I placed pieces of 3/4-inch ply above and below to give the sled support when it was cutting, but the edges didn’t line up flush. Some spots the cedar was higher and other spots the cedar was lower. I used a number of screws along the plywood to try to get it as flush with the frame as possible and didn’t want to screw into the cedar. During my first cut attempt, I wasn’t achieving the depth I was going after and it was uneven (bottom part of the cuts were “okay” but the top parts were nonexistent. I figured out that it was due to the differences in height between the cedar and the support pieces of ply. I put one screw near the bottom edge of the middle of the cedar to try to get it closer to the frame and it helped a lot, but I ended up manually applying some pressure to the router and helping it around in order to achieve the desired cut.
So, any suggestions on how to deal with imperfect wood like this? Besides using screws (whose holes then have to be addressed) I don’t readily see a way of “pushing” the board into the frame to take out the bow. I couldn’t flip it over and use the other side as that was the rough cut side and I needed to profile the smooth side.
From where I’m at there are a few ways. 1 - use thinner supports on screws so you can adjust the surrounding support material in and out. 2 - long way do a face cut 1st over the entire surface. 3 - put holes in it and then fill them. 4- pre process the wood - put it under pressure to flatten it first. I plan to use 1/4 dowels to hold many of my parts.
- Joint/plane it flat. #2 is effectively a really time intensive way of doing that.
Unless I’m missing something, this is kind of a known issue with working with wood, and it’s been solved for a couple hundred years at least. And trying to coax a warped board temporarily flat, and hope it stays flat for a long series of machining operations has a decent probability of leading to saying lots of bad words at high volume.
I was wondering if I could do something from the back side of the wood… but in screws from the back that are shirt enough to not go all the way through the material and have them pull the wood down to the frame. A problem is figuring out how to put them in accurately so as to avoid putting them where you are doing a cut.
What if you oversized the piece you were cutting, then ran the long edges through a table saw to bevel them 30 degrees or so. Then you could use french cleats to hold your workpiece flat. The best part is that they would provide the sled with a surface to ride along near the edges of the piece.
Not sure if this’ll work, I haven’t tried this myself. Alternatively, you could secure the piece with brad nails. They will create a much smaller hole to fill. You will still have to place them around your cuts, but if you did a quick layout of the part you should be able to figure out where the bit will be.
Double sided tape, if thin enough. Vacuum table, could probably rig something small with pegboard and s shop vac. Mist the concave (curved up at the edges side) with water and wait.
If you have access to a bigger shop then a jointer and thickness planer. Then there’s those handheld power planners (need one here for a slab table project from a fallen yard white pine). For the old school guys there’s a wide assortment of hand planes, or even a jacknife and lots of time.
There’s been warped wood since the first board, and compensation techniques since the first cave man chipped a rock to level it
Route a template out of thin (1/4" mdf?) material and double stick tape it to the cedar slab. Hand route lettering.
A cabinet maker would plane and joint half of the wood away to make it straight. I think that’s a little sad.
this is where the raptor plastic nails are such a nice thing, you can mill right
through them. You do want to put them in parts that will end up painted or cut
away so you don’t see the small amount of plastic, but it’s very nice to not
have to worry about hittng a nail.
Those look pretty useful. A box of those are on my to-buy list to try them out!