More Experiments with Chipbreakers
This week I’ve been surfacing a lot of wood by hand, from pedestrian sugar pine to funky metals that have wood-like properties (e.g. purpleheart). And all the while I have been testing, testing, testing things with my chipbreakers and the cutting angle of the iron of my handplane.
Huh? You might say. Yes, there might be a relationship.
So I’ve been up at Lie-Nielsen Toolworks in Warren, Maine, this week to teach classes, shoot a video and demonstrate at the company’s open house. During the evenings, I’ve been debating a lot of theories about wood failure with Deneb Puchalski and Thomas Lie-Nielsen. Here are some highlights.
1. Why does setting the chipbreaker crazy close reduce tear-out? Deneb of Lie-Nielsen has a good theory. He thinks that a closely set breaker “fools” the wood into thinking that it is being planed by a high-angle plane. So a 45° plane with a 25° breaker suddenly acts like a 70° plane. This makes sense.
2. Do you need a tight mouth with a close-set breaker?
3. Do you need a high-angle plane with a close-set chipbreaker?
4. What effect does honing the breaker have? And what angle should you use?
So during the last week, here’s what I did. I worked with two smoothing planes. One with a 45° frog. One with a 55° frog. I honed the cutting edge the same and tapped the chipbreaker as close as I dared to the edge. I also did some work with a bevel-up jack plane honed at 50° so it had an effective cutting angle of 62°. All the planes had mouth apertures of 1/16”, which is pretty wide open.
On the smoothing planes I honed a 50° angle on the chipbreakers. So if Deneb’s theory was correct, I actually had three different planes. One was cutting at 62°. One was at 95°. The third was at 105°.
Then Deneb, Dave Jeske of Blue Spruce Toolworks and I put the planes to use on a variety of woods. We tried reverse-grain cherry. It was no challenge for any of the planes. Then curly bird’s-eye maple, planed against the grain. Again, no problem. Ancient fossilized purpleheart. Nope. No difference. Then a board that we were told was unplanable: big furry, roey mahogany.
Again, all the planes handled the wood with no real problems.
Finally, I pulled a piece of wood out of the trash. It was cherry with a tight swirled knot in it. There was a crapload of grain reversal around the knot. Lots of quartersawn grain rippling across the face.
In other words, it was fit to be burned.
After dressing the wood with a toothing plane we put the 62° plane to it. It cleaned up all of the board except a narrow band of tearing along one of the quartersawn ripples. Then we took the 95° plane to it. No joy. But the 105° plane cleaned it up nicely. And it left a typical planed surface – it didn’t look like it had been scraped.
So perhaps Deneb has something. Or my 105° plane is haunted by a small dwarf or troll.
— Christopher Schwarz
Read more on my chipbreaker experiments here.