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View Full Version : Usuba Geometry - A Curiosity



Seth
07-05-2013, 06:11 PM
So I always wondered about this geometry. If the ura lays flat on the quartz countertop and there is a distal taper, and the blade is a uniform height, then the shinogi line has to curve up. I finally noticed that while the spine looks like a distal taper, the area around the shinogi in the distal area of the knife actually gets thicker - at least on two of my usubas. The Nenohi does not do this and the grind is fubar; actually concave on the bevel in the distal portion. Go figure....

schanop
07-05-2013, 07:01 PM
I think Shigefusa usuba quite clearly illustrate what you are saying from the very triangular shape at the tip and the more than usual usuba distal taper on the spine.

https://lh3.googleusercontent.com/-yE5N-kApl9o/T4oywq9r3UI/AAAAAAAAAhY/6pNsum5Sb-M/s640/PICT0130.jpg
http://pic80.picturetrail.com/VOL2041/11274169/24359737/406731803.jpg

Seth
07-06-2013, 12:23 AM
I never thought about it much till I had problems with the Nenohi. Then I got two shigs, one of each and it is clear what the geometry is supposed to look like. Too bad the Nenohi cost so much but I am slowly bringing it into a workable shape.

As an aside, it rained shigs today, great fun. I ordered one like yours from jww about 1 1/2 years ago and they kept postponing delivery. I got an email from them about delivery and I asked them if they were for real this time and they said no, not till September. So I ordered a Kamagata from Maxim and today both of them showed up even though the jww was not supposed to. Loved getting two cool knives in one day but my credit card is on life support!