I’ve been wanting a Naga-dai-kanna (jack plane) for a while now. For some reason it never occurred to me to use the 60mm blade that I already have for my smoothing plane and cut a new dai. So, that’s what I did. Before making my first dai I made an osaehiki nokogiri, the saw used to cut the blade bedding lines. Its very sweet, the first shavings from a new tool, after having to make a tool to make the tool. You get it, its a long and satisfying way to fill a shop with tools.
The plane measures 16″ in length, with a 40/60 distribution front to back from the cutting edge.
Let me say straight off, I think I made a lot of mistakes, hopefully you can learn from them. I didn’t have any plainsawn oak thick enough to make a dai from so I laminated one up from a couple of pieces of left-over red oak flooring. Its definitely not the same as Japanese white oak. There are these soft ring-porous areas in red oak (and the pieces in my dai) that I’m sure are not going to wear well in use. I made my layout with a marking knife when pen would have been more than adequate. The bedding angle is 38 degrees, and the koppa-gaeshi (small vertical line by the blade angle line) was made vertical. My primary source for this project was Toshio Odate’s “Japanese Woodworking Tools”.
Jay Van Arsdale’s making a dai was also very helpful, especially where they differ.
I started by mortising in from the top about three quarters of the way with a 1″ bench chisel, riding the bevel. I used the lines I had drawn on the sides as a rough guide and took care to cut shallower angles than was necessary.
Working from the bottom I cut between the blade angle line and the blade bedding line. I didn’t mark out the extra space for the shaving to pass through, figuring to pare it open once the blade was seated. I started by using the sokozarai-nomi to clean the waste, but in the end just started using a 6mm mortise chisel, bevel down. I cut to the depth of the koppa gaeshi.
Flipping it back over I pared back to the layout lines, but at a slightly shallower angle than necessary, and slowly pared down the angles. I started with paring the mouth opening towards the back of the plane (the surface with the chisel in the picture) so that if I pushed too hard and gouged the blade bed there would be enough material left to remove it.
The surfaces came out pleasingly accurate and smooth, ready for the side grooves to be cut.
I started the first cut and my little home made saw was binding badly. I remembered Jason had left a comment at some point about special files for hon-metate that raised a little burr on no set dozuki, so I made a light filing pass on the osaehiki-noko. It worked so much better with a little burr from filling. It was easy to make the cuts along the blade bed with that nicely pared surface to jig the saw plate.
For the blade angle line cuts I used the edge of the mouth on the sole to keep the blade vertical and on point and cut to my layout line on the top. I’m really pleased with how the new saw worked out, definitely worth making.
For cleaning the waste between the cuts I used a fine 1/8″ detail chisel, but an 1/8″ mortise chisel would have been better. This oak is tough stuff and a tiny delicate chisel can’t take heavy cuts without bending from the force.
From there I bedded the blade. What I did not notice was that the top of the blade is heavily concave. I didn’t leave myself enough wood when I marked the blade thickness line in layout. The process of bedding the blade was cut short because the blade became too loose before the top of the iron was fully seated to the block. I should have held the blade at least 1/4″ back from the mouth when marking the blade thickness line.
But what the heck, it took an okay shaving even with the poor bedding. I could feel chatter at the cutting edge, but decided to forge ahead and get the sub-blade holding pin drilled. Odate gives some obscure directions for figuring out the placement of the hole, but I decided to just trace the sub-blade on the blade angle line and use that line to place the hole. Perhaps I should have center drilled it first with a 1/16″ bit, my hole wondered terribly. At least the error is in a direction I can correct by filing.
Gotta love the warm glow of brass rod. Classy. Something else was bothering me though. I had been reading on Chris Hall’s blog “The Carpentry Way” about warped conditions on the back of new Japanese plane irons. Can you see how the blade is hitting the blade angle line with a gap in the middle? I didn’t do a good job flattening the back, and couldn’t of with so much concavity in the back of the blade without ruining the ura. I thought I had a basically decent plane iron, but cutting this dai forced me to really look at the blade in new light.
What ends up happening is that the blade wants to dig into the bedding on its back, effectively loosening the blade and changing the bedding angle. I ended up stoning the sharp edges off of the mimi where they meet the back, and it seemed to help somewhat with the digging in. At this point I had learned a great deal, but didn’t have a plane that felt like it worked well. I had to sort out the poor blade bedding.
I cut the thinnest veneer I could with a handsaw from another piece of oak and glued it in the bed. You can see how after scraping in the blade once more I exposed the original wood on either side where the blade back was the highest. My god, what a difference a properly bedded blade makes, it even fixed a poor fit of the sub-blade against the sub-blade holding pin. The naga-dai-kanna does seem to take more time to condition the sole, but that is something I can now look forward to as I get to know the use of this new tool. And yes, it gets a board very, very flat.