Shaping Japanese blades (niku)

F

fried

Joined
Feb 20, 2006
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I don't post very often but would like some advice for those of you who do Japanese style blades. I just received some W2 from Don Hanson and was going to venture into a Japanese tanto or wakizashi. What is the best way to shape the niku (convex) on the blade? I don't have waterstones and was thinking slack belt and files with a hybrid hand sanding finish. I'm not quite sure the best and most efficient way to go about it. I know tanto's don't usually have much convex but would like to try. I usually do all flat grinds so this is new to me.

Thanks,
 
A lot of the traditional tantos I've seen do have quite a bit of convex to them; the ones in museums at least.

I'm smalltime and don't have a terribly efficient process -- but I do the majority of my stock removal with a slack belt and then do the final shaping with waterstones. Nihonzashi (google it) has a great selection of premium waterstones of all grits. I have typically used a Golden Lobster 80-grit stone for the majority of the hand shaping in the past.

I'm also experimenting with using 3-M 40 grit micro finishing film affixed to a piece of key-stock. The blade is held flat against the ground. Again it's slow going -- but I like the results.
 
do the majority of your stock removel by making small flat grinds. the blade will have a fauceted look when you're done. now you can blend these into a smooth finish using a slack belt. with this method you ca acheive any geometry you want and it is similar to what is traditionally done with water stones.
 
Ditto Bill's advice.

Take it down in segments. When all is a little fatter than desired, start rounding it into a continuous curve.

On a tanto, look at some photos of true Japanese styles. The slanted tip and flat grinds on the American tanto are not the classical look. I often use the comparison of a cross between a fillet knife and a wakizaski to describe a tanto. The blade curves up to the pointed tip gradually, not suddenly and blunt.

Also, while a tanto is traditionally measured at less than one foot ( < shaku), that does not mean the blade needs to be 11.5" long. A nice 8" blade with a graceful curve and about 1.25" wide in the center will make a good project. The cross section in the center should resemble a pumpkin seed or apple seed.

I'll try and pull one out of the shop and shoot a photo later.
 
Thanks for the info. I always wondered how they got that convex (niku) using files and stones. I assume there is a rolling type motion on the file/stone to set the initial shape and get the curve. I'm looking forward to the process. Would love to try the waterstones sometime but darn they are expensive.
 
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