Differential Hardening Sunnobi Tanto

Sunnobi tanto are larger than ordinary tanto (nagasa above 1 shaku) and may have sori similar to ko-wakizashi. Read more about the process of yaki-ire.

1. Using approximately a 1:1:1 mixture of natural clay, polishing stone powder and ground charcoal to mask the back of a hand forged blade about 1-1.5mm thick to slow down the cooling rate.
2. Brushing on a thin slip layer with extra charcoal added along the exposed edge to speed up the cooling rate and protect from carbon loss.
3. Carefully heating in a charcoal forge supplied by air from a fuigo box bellows until the edge reaches critical temperature.
4. Plunging edge-first into cold rainwater to cool the blade quickly and harden the edge while leaving the rest tough and resilient.
5. Testing for successful hardening with a file and then removing the clay with a mild steel scraper.
6. Slightly reheating the blade over the flames to temper the edge.
7. Test polishing on a coarse Japanese waterstone to check the hamon.

Making a Swordsmith Anvil from Scrap

A Japanese swordsmith style anvil made from junkyard scrap. The two side pieces are cast steel or iron John Deere 8255C rear counterweights from a shovel dozer. They weigh about 200-240lbs each and measure about 2 1/8″ x 14 3/4″ x 25″. There is a ‘T’ shaped face and stem that extends to the ground between the plates made from welded spring or tool steel and weighs about 70lbs.

The face is about 1 3/8″ x 6″ x 15 1/4″ and has a pritchel hole in it and a sharp edge for cutting on one corner. The combined weight of the plates bolted onto the face and stem should be between 475 and 520lbs. The finished anvil should sit 7-7.5 sun from the ground or from the seat height. See the whole forge building process here.