Canadian Woodworking

The thickness planer

Author: Hendrik Varju
Published: August September 2002
dewalt thickness planer
dewalt thickness planer

The thickness planer is one of the safest woodworking machines you will work with.



A cutterhead spins in the centre while infeed and outfeed rollers pull the board through. You don’t need to hold onto the board once the infeed roller has taken hold of it.

There are only a couple of safety issues with this machine. When you feed a board in, feed it in smoothly, gently, and as flat to the machine’s bed as possible. Put some downward pressure on the board directly on the infeed side of the bed as you feed it in.

As with the jointer, kickback situations are rare with this machine. It is only likely to occur with loose knots, nails or other foreign objects. Check over the board with a magnetic wand if it is something questionable like barn board. Loose knots can be removed or glued in before planing to avoid projectiles. A five-minute epoxy glue will not hold up your production time.

As always, a kickback would mean that the board is thrown backwards, so never stand directly behind the board if you can help it. Stand a few inches to one side as you feed it in. Also, be sure that your hands are on top or on the sides of the board, but not underneath. The infeed roller pushes down on the board with great force, so you will be injured if a finger is caught underneath as you feed it in.


One use of a thickness planer is to plane like parts to the same final thickness. However, no matter how carefully you install your planer knives into the cutterhead, it is virtually guaranteed that they will not be set to the exact same height at both ends. So if you plane one board at the extreme left side of the bed and another at the extreme right, they aren’t likely to be exactly the same thickness.

For this reason, you should feed like boards through the same part of the machine for the final pass. It doesn’t matter if you choose the left side, right side or middle, but just stick to one location. The usual procedure is to just randomly select any part of the cutterhead when doing your initial passes or rough planing. This is important too, as you want to wear all parts of the knives evenly. But when you are ready for the last pass, which will establish your final thickness, run all of your boards through, one at a time, in the same area of the cutterhead. If your planer has an anti-snipe lock mechanism, lock it in just before this last pass.


One of your enemies when planing or jointing is tear-out. I touched on the issue of determining the proper feed direction in my last article on jointing. Unfortunately, the grain in a single board often changes direction somewhere along its length, sometimes more than once. While you can hand plane in two directions, planers and jointers can’t. So you will find that sometimes you have to choose the lesser of two evils and still have some tear-out somewhere on the board.

Jointers usually do a better job of planing in the wrong direction than a thickness planer for the sole reason that you control the feed speed of a jointer. You can push a board very slowly to reduce tear-out, but even the slowest speed on a two-speed planer can be too fast.

There are three strategies I use when tear-out is unavoidable. Firstly, the sharper the knives, the better the quality of cut, even against the grain. So newly sharpened knives are a good idea on difficult woods.

Secondly, you can feed a board through your planer on a skewed angle, rather than pointing straight ahead. Don’t angle it too far, or the back end will catch on the frame of the machine instead of staying on the bed. However, skewing the board actually decreases the cutting angle of the knives and gives you a cleaner “shearing” cut. This technique is often used when hand planing as well.

Thirdly, and only as a last resort, you can wipe the surface of the board with a wet rag just before feeding it into your planer. This softens the wood fibres just enough to avoid most tear-out. This is not something I want to do unless I have no other choice, as I don’t want to wet my planer. But I will do it as a last resort on the final pass of a really stubborn board. Don’t bother on the rough passes – only on the final pass. I will usually angle the board as well as wetting it, to give myself two chances at avoiding tear-out at the same time.

Next issue Hendrik gives three tips on using your bandsaw.

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