If you’re interested in woodworking, read on!
I’ve been thinking of making a hand plane out of wood and was doing some reading, ran across a post titled Setting a Cap Iron recently and by itself it was interesting, but much more so when you look at the video below. A cap iron – also known as a chip breaker – works with the blade when planing by reducing vibration at the cutting edge and it turns (breaks) the shaving (the chip).
In the image below the blade is on the bottom, cap iron on top, cutting edge on the left. See how close the two edges are?
The first part of working with a plane is obvious if not easy, get the blade sharp enough and positioned correctly to take a thin, even cut. The second part isn’t as obvious until its your wood, and that is whether you’re getting a surface that is smooth. Smooth is the key. The reason it may not be smooth is called tear-out. Wood isn’t perfectly uniform. Often the prettier the wood, the less perfect it is as far as the grain. Run a plane across that kind of wood and it will literally tear out small chunks of wood. What this video shows is how adjusting the setting of the iron, both distance from the edge and the angle, affect the final cut.
The video was done in Japan and has since been sub-titled. It’s about 17 minutes,but if you’re not totally awed just skip through,you’ll see them trying a few different settings that you see in action at a microscopic level. You also see that those settings vary by .1mm – that is 0.00393701 of an inch!
As you watch you’ll see the shaving curling up to the right of the blade, it should be thin and uniform. At the same time watch the behavior of the wood just behind (to the left) of the cutting edge. At some settings you’ll see it”s smooth, in others you’ll see the wood popping up and falling back and leaving gaps – that is the tear out.
I definitely have a deeper understanding of how it all works together now.