I’m not gonna sugar coat it, I have struggled with the Japanese common plane. Getting it to cut is easy. Getting it to cut consistently and predictably, that’s a whole other thing all together. The learning curve is steep and my lack of understanding and skill has made it a slow process. Past is past and I have resolved to remedy this shortcoming.
As I told you in a previous post, I received my first two kanna as a Christmas gift several years ago. Not long after that I purchased a used kanna off of eBay in hopes that it would be in a usable state and that I could learn something from it. Soon after opening the package though, I was bitterly disappointed. The blade was great, the dai on the other hand was a Greek tragedy in wood.
The dai was twisted almost a full 1/4″ along its length and the mouth/throat opening was big enough to drag a cat through. When I inserted the blade into the dai, it almost fell completely through. While not exactly the leaning opportunity I was hoping for, it has proved useful. Over the years I have trued the block and shimmed the bed to get the plane at least usable. I used the blade for sharpening practice and to keep it in good condition. Still, it has never become a usable tool. Until now.
In one of his videos Jay van Arsdale states that he likes to make new dai for his plane blades and bed the blade at 50deg. This makes the plane useful for a wide range of woods and eliminates the need for the secondary blade/chip breaker. Hmmm. So I re-read the dai making section of Odate’s book. Hmmm.
Up until the early 1900’s the Japanese common plane was a single bladed tool, no chip breaker. The addition of the chip breaker is speculated to be a result of a few factors. The result of western influence, the lack of skilled craftsmen and the lack of quality timber are often listed as factors leading to the addition of the chip breaker. Here is the tricky bit. To be effective the chip breaker must be set 0.3mm or less away from the cutting edge. It’s not as hard as it sounds, but it takes practice.
With those few pieces of information I began examining how I use western style planes and speculating.
Generally western plane blades are bedded at 45deg. The Bailey pattern planes have a cap iron (sudo chip breaker) and the more modern versions have actual functioning chip breakers. When the chip breaker is properly set on western or Japanese plane the shaving ejected is quite different. Instead of the familiar curled shaving a continuous ribbon of wood is ejected from the plane. I have to admit that it is quite satisfying to set a plane up to this way, but I have rarely, if ever had the need to do so. The idea is that the chip breaker allows the planing of difficult grain and reduces tear out.
I work mostly in radiata pine, SYP, fir and SPF (spruce,pine,fir) construction lumber and have had little need for such a fine plane setting as described above. What I have found is that the 45deg bed angle of western planes and a sharp blade will serve me quite well in all but the most gnarly of grain. So I wondered if van Arsdale’s recommendation of a 50deg bedding angle would work for me?
The only way to find out was to make a new dai for my orphaned Japanese plane blade. It just so happens that I have a small stash of well seasoned 1-1/4″ thick white oak in the shop. So after work one evening this week I knocked out a new dai.
I made a few mistakes, but I learned a lot. I’m not going to go into the how of this build, but focus on the results of this first experiment.
The 50deg blade angle works well and once I had the sole of the new dai conditioned I was able to produce a wispy shaving. My sharpening needs work though.
Then I set the cut a little deeper.
This new dai has a tight mouth/throat opening and this plays a role in controlling any tendency for tear out.
As a comparison I set up one of my original planes complete with the chip breaker properly set. OK, I could probably get the chip breaker set a little fine, but I wasn’t going to push my luck. This blade is bedded at around 40deg.
So here is what I learned. For starters, I learned that I could actually make a dai. I’m real happy with that. The 50deg bedding angle is OK, but there is a sacrifice in the surface quality that it produces. With a little more sharpening I could improve on that, but I don’t think it will produce a smooth polished surface anywhere near the quality of the lower angle plane.
So tomorrow I’ll make another dai. This time I’ll bed the blade at 45deg and see how that plays out.