I'm interested in trying my hand at making a Japanese plane iron. Does anyone know if the back is hollowed by grinding or hammering? Which leads into the second question: How thick should the tool steel layer be on, say, a 3/16" thick iron?
The blade is laminated flat. Then a special swaging tool is used to bend the edge down. Then it is ground on stones to an edge. When you have sharpened it enough to get past the swaged part, you swage it again.
That is why they laminate the really hard edge steel to a soft mild steel backer.
I have a very good book on Japanese joinery that shows the whole process.
Both. Hammering is traditional and the main method for planes. Chisels are now a mixture - grinding for the low end ones, hammering for the better ones or those with itame hada. When they're worn back to the hollow, the forged ones are re-shaped by cold tapping, or the ground ones are re-ground.
Depends on the steel you're using.
My plane irons are between just under 1/4" and just over 5/16" thick. Their hard steel varies between about 1/6 and 1/4 of this, with the better and thicker ones also being proportionally thicker. I also have some Japanese irons (Samurai brand) made for Western Bailey-pattern planes which are thinner, but maintain similar proportions.
I presume you're failiar with Japan Woodworker etc., but another vendor worth a look is Steve Knight (I have one of his Japanese-ironed smoothers)
A couple of highly recommended books are: Toshio Odate's "Japanese Woodworking Tools"
Thanks for the reply. My first thought of steels is to give it a try with the steel I have on hand: some 1018 and O2. I'll check out those books - I've looked at the titles before and passed, I'll have to take another look.
Hey Eide n'all, Here is what and how i know about japanese wood working tools. About 10 years ago I had the chance to work with a Japanese toolmaker for a weekend. His professional name is Yataiki. His specialty is saw making but he makes all sorts of edged tools as well. Anyway, He showed me his process for making a yari kanna which is sort of a cross between a plane and a chisel. Laminated steel, hollowed back, spear shaped (ie yari) with integral iron handle. When it came time to hollow the back he a wooden mallet over a wood stump. This prevents hammer marks being left in the hollow area which are hard to remove. In my first note to the group on this subject I mentioned the use of a tool called a "sen" This really is a vital part of making any japanese tool or weapon. They are extremely efficient stock removal tools and are made in a wide variety of sizes and shapes to suit the purpose at hand. Some are tiny, like .5" wide some even smaller for forming grooves like in a sword blade. Other sen are several inches wide for planing off wide surfaces like when making a saw blade. This is the way to go on a chisel back. Don't be to concerned with the loss of material as the hollow only needs to be .020" or so. One interesting thing is that this is one of the few Japanese tools that is pushed rather than pulled in use. A sen for hollowing a plane blade would be a little narrower than the hollow itself, maybe 1.25" and about 1" from cutting edge to back edge. The face of the tool would have a slight radius and the face angle would be about 55?- 60?. As I have said this thing looks like a draw knife with handles on each side. If you started with 3/4 x1/2" stock about 14" long, welded a piece of 1095 in the middle you would be on your way. Draw the handle material out to about
16" with pointy ends to drive on some wooden grips. Also the handles droop slightly below the cutting plane for more better control in use. I know a picture of these tools would be nice but I have not found many. That sword making book others have mentioned shows it in use but it is not talked about in detail. Really and for true this is the way those little guys do it.
Eide, Looks can be deceiving after forge welding parts together. What appears to be 1/16" thickness is probably closer to 1/8". I am not really sure of just how thick a piece of tool steel you should begin with. The size of the finished plane blade will dictate that. I would guess a piece of high carbon no less than 1/8 or 5/32", laminated to a
1/4 or 5/16 piece of low carb or wrought iron (if you can find some) should yield a average sized plane blade. A considerable amount of metal is lost when welding and forging. I would always prefer extra cold work instead of a blade that is to lean. There is very little real working data on this subject most is aimed at woodworkers and NOT smiths. I sent another email about forging a yari kanna and after looking over my notes from 10 years ago i realized I made a mistake in describing how the hollow is formed. Yataiki uses a mini anvil made from a chunk of 4"x4" steel about 10" long, set on end. The corners are rounded off. When forming the hollow the plane blade is held at an angle against the rounded edge of the block (tool steel side down!) and lightly hammered on the top surface at a low heat (dull red). It does not take much to form the hollow and NO metal is lost at this point. The "sen' is used to true up the surface and refine the hollow. Not much metal needs to be removed, just enough to remove all the scale. You have embarked on a project that will take time and patience. Expect to add to your scrap pile before you get a good blade. Also, I have never had good results welding O-1. It seems to be rather hot short and unforgiving. I would try some W-1 or as Yataiki suggested "old lawn mower blades" Good luck dude,