Knots and power tools

[paul simonson]

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Hi all,
Fairly new woodworker here. I'm using the machine above, which you'd call a thicknesser or planer depending where you live in the world. Is it ok to put wood through it that has a knot in? Is it ok? Or not? (no puns please lol) Thanks!

[Joe Hollis]

Hello Paul,

I'm no planer expert, but I owned two small 12" portable planers before I bought the jointer/planer unit I have now. On a few occasions I planed wood with knots in it, and in ALL cases suffered chips in the knives. They were either the standard quality knives that came with the planer when purchased, or in one case premium cobalt content knives. Both knife sets did not take kindly to the knots, and punished me for it...

Regards,

Joe H.

[Dan Friedrichs]

If the knot is stable, it's fine. If the knot could come loose, it could seriously damage the planer. Some use CA glue on a knot to minimize the chances of it coming loose.

You probably don't want the knot to appear in the finished piece, so it's best to cut it out, if possible. That said, I've done some more rustic pieces where I've left knots in place and generally don't get too nervous about running them through the planer if it doesn't seem like there's a huge risk of them breaking free.

[George Bokros]

A large knot like what you show I would not put through my planer. Small pin knots I do without fear of damage. Like Dan said you probably don't want it in your project anyway so cut it out.

[William Young]

I've done it for years with my Dewalt planer. Two stipulations: as mentioned above, make sure the knots are tight. Glue them in if necessary. Also, if you have knots, set the depth of cut as shallow as you can. Chip-out is common in the area around the knots. Shallow cuts will also help minimize this.

[Tim Bueler]

I work with knotty pine, alder, oak and hickory all the time. The knot you show has a dark circle all around the outside. This is a knot I would either use CA glue or epoxy depending on how large the gap(s). When knots come out it is not pleasant in any way for man nor machine. Interestingly, and anecdotally, the knots of the pine are worse to plane that the knots in hickory. Also, you'll get less severe reactions with a segmented planer head if you have a choice. Even on tight knots you'll sometimes get a chunk that comes out and causes some displeasure. Noise, jumping, cutter dings, etc. Shallow cuts and, if an option, slower feed rate.