Hello everyone!
I ‘finished’ three cutting boards I made this weekend, but I noticed that all three have the exact same unevenness in them. Two corners (opposite of each other) are lower than the other two, causing a rocking in the boards.
Does anyone have any tips on getting these things flat? I tried using a random orbit sander to get the corners down, but that doesn’t seem to have worked very well.
I did use the drum sander, which I figured would get them flat enough… but apparently not.
If they are not cross grain or end grain, you can use the planer.
If they are cross or end grain, then people usually use the CNC. Or you can build a router sled and do the same thing by hand. You’ll need a fly cutter bit.
Any tool that compresses the work piece will deflect the work piece. The new joiner doesn’t compress the work piece but may not be wide enough to surface your cutting board
The CNC will do this but the material needs to be secured to the bed of the CNC machine before machining it. You will need to put shims under the high corners of the cutting board (between the bed and the gaps) to get it level BEFORE you clamp it to the bed - otherwise it will just spring back to the twisted condition after machining it.
Run a CNC surfacing bit over the board to get it flat. Turn the board over and it should be flat and not rock. Then machine the other side that was not machined so everything is a uniform thickness.
There might still be a sled for the thickness planer somewhere that can do much the same thing without going through the learning curve of the CNC, Shim up the space between the sled bed and cutting board so it doesn’t wobble and feed it through taking light cuts off the board (if it fits)
Finally, there is a process to taking the warp out of wood pieces with a hand plane. A plane with a very sharp plane iron makes this route a pleasant journey. Two simple sticks called “winding sticks”. Placed them at both ends of the board and then sight down the surface of the boards aligning the top surface of the winding sticks with your eyeballs. Differences (twist) in the surface are quickly revealed. A few licks with the plane will take off 1/32" on the high spots. Work both high corners until the winding sticks are parallel front to back. A wood vise and bench dogs allow this to go quickly.
YouTube videos tend to be overly pretentious and preachy on this topic. Here is one that is no better than any others but demonstrates the principles well enough.
If you haven’t taken the CNC class there is also a router sled somewhere in the shop that I have used with a surfacing bit for end grain cutting boards - because you can’t plane them
concept is very much replicating what the CNC would do
To add to the sled planer idea, you can do this on the drum sander as well. Place your board on a sled, shim it, and run it through the sander. It will be a slower process, but should work all the same.
The best method for securing onto the CNC bed is probably the superglue-and-painter’s-tape method.
In addition to not requiring screws or surface clamps, since this isn’t a clamp, it won’t pull the board flat. Pulling it flat would be undesirable as the point is to level that off in the unclamped state.
These are edge (long grain) cutting boards I did run all of them through both the planer and the drum sander, but that didn’t appear to help.
The CNC sounds like a great idea…but I’m not trained in it yet 
I’m thinking I’ll look into a planer jig like @David78737 mentioned. If that doesn’t work out I may try the hand plane route with winding sticks. I have seen videos of people using a router to flatten stuff though…
Thanks again for the advice everyone 
There are planning sleds. The router sled that was here appears to be a casualty of work day. It was used once or twice a year and still needed walls to run on.
If you’re wanting to flatten them on the CNC, I would bet someone could help you out with that.
I actually ended up using the jointer (thanks for the suggestion @David78737!)
It was so easy to flatten that way that it almost felt like cheating lol. Love how wide the Laguna is.
Jointer is great as long as its not more than twice as wide as the jointer blade. Another cheater way to work it is to use the screw in rubber feet on the bottom side. Then you can use a washer to shim the two high sides and the washer is hidden under the rubber foot. Of course this limits the cutting board to only one side… buuuuuuut it does allow air circulation around the whole board and helps prevent warping if the board stays wet. Also on bigger boards the rubber feet helps “stick” the board to the counter.
Yeah my backup if everything failed was to make some plugs using tarkin (out of the off cuts) and then using those as little feet.
I also have some of those rubber feet for making bathmats, they work great! Not the look I was going for on a cutting board though