Planer Sled

While I am in between 'big' projects, I decided to make a 'quick' kitchen table to replace our cheap table that we bought for $60 when we first got married 7 years ago. The top will be made up of solid panels, and the lumber I had for the top is not flat, so I need to flatten it before gluing up the top.

The boards are wide enough that I don't want to rip them all done to 6" to send them through the jointer for flattening. Since I lack any hand tools to flatten them the next easiest solution is the planer. I decided to make up a quick planer sled to run the boards through the planer and flatten them.

A planer sled supports the board you want to flatten as you pass it through the planer, causing the planer to only take off the 'high' spots on the board and flatten it out. If you send a cupped board through a planer, the planer will compress the 'cupping' of the board as it planes, taking off the 'high' and 'low' spots and not flattening the board, only reducing it's thickness. A planer sled will prevent the planer from compressing the 'cup' and force the planer to correctly flatten the board.

First - dig around the workshop and find a flat board that is wider and longer than the boards you want to flatten. I found a piece of melamine shelving that fit the bill. You will be fastening your boards to flatten to this flat piece and running them through the planer, so it has to be narrow enough to fit through your planer.

Next, glue, nail, screw or otherwise fasten a back onto one end of your flat board - this piece will keep the board you are flattening from sliding off the back of the sled.

Your sled is now complete - let's put it to use.

Now, place the board you want to flatten onto the sled and determine where you need to add support to the board. In the board below you can see I need support in the middle and on the left hand edge.

Now, flip the board over and add some gobs of glue from a hot glue gun. I made the gobs about 3/4" in diameter. Too much glue is better than not enough.

Flip the board back over before the glue dries and press it down in place on the planer sled. Wait a minute or two for the glue to dry, then you are ready to send the board through the planer. In the picture below you can see a bit of glue sticking out the side of the board.

Now, send the board through the planer. You can see in the picture below the planer is only removing material from the 'high' points on the board - the center of the board in this case. If I did not use a planer sled, the board would have been smooshed flat as it was sent through the planer, but then bounced back up when it came out the other end. Afterwards I would have a thinner, but still cupped board.

After a number of passes through the planer I have one side of the board flat. I can now flip the board over and run it through the planer to flatten the other side.

To separate the board from the sled, use a old chisel to pry it off, then use that same old chisel to pop off the gobs of glue. Obviously you'll want to remove that glue before sending your board back through the planer.