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While I was planing down a plank of Cedar this evening I noticed that the plane did not slide through the knotty wood, that it was a harsh stop. It made me wonder whether I should attempt to plane wood that has knots in it.
Does knot wood cause a hand plane's blade to become duller faster than regular wood?
Knots do in fact dull any cutter faster than the surrounding wood does because they are harder. Knots don't leave severe nicks though.
The secret to good hand planing is to sharpen often - sharpness is the best thing to improve results. When encountering knots it is helpful to skew the plane a bit and approach the knot at an angle but having the blade sharp is important.
I find that I need to sharpen every time I intend to use the plane if I know that I will use it for more than a few passes. When I say 'sharpen' I don't mean grind, coarse stone, medium stone, fine stone - all that rigamarole. I just mean 'honing', i.e., using the fine stone and then strop it on some leather.
At this point, I'll stop because sharpening is another huge topic and I don't want to go off-topic. Suffice it to say that knots are indeed hard to plane but frequent honing helps.
Side note: when using a surface planer (big power tool), if the knives are not new and sharp, they can rip the knots completely out. You can hear them rattling around inside the planer before then find their way out. This is startling when it happens. I should replace my planer knives more often than I do because in my case, it seems that the rollers do not pull the work through as well if the knives are not sharp. This is probably unique to the planer I have.
Yes, it does, they tend to be harder and the grain also is in a different orientation. often planing a knot is similar to planing the end grain. This of course is harder on the blade and thus more wear. I have even noticed it on my planer.
Whether you quit planing knots is up to you, it just means you have to sharpen the blade more often. Which is something I know I need to become more proficient in.
Sure you should continue hand planing wood with knots. Your experience with the plane stopping is common, and yes, knots will dull a blade faster, and can create some small nicks in the edge. Decreasing the cutting depth is the best way to handle the knots. You can see the knots in the wood surface, so adjust the blade depth accordingly.
There are a couple of ways to approach knots. They can be planed down below the surface, then the rest of the surface planed down to them, and then final passes over the whole surface, or the whole surface can be planed down at once. I usually do the latter. Typically knots will have reversing grain which will tear out with the typical 45° bench plane. Hand scrapers, scraper planes, and high angle smoothers can be used to clean up these areas.
Does knot wood cause a hand plane's blade to become duller faster than regular wood?
As already answered yes they will. In rare occurrences they have been known to chip the edge, but I stress this is very rare.
In addition to having your iron as sharp as you can make it one tip not given above is dampening the knots to soften them (can also be useful planing end grain). I think the majority of users will by necessity have to resort to other means to do their final smoothing of knotty wood, for most this will mean sanding but ideally most or all of the work should be tackled with a scraper.
