Walter Sorrells, master knife-maker, demonstrates how he made a modern defensive knife for jiujitsu coach extraordinaire, John Danaher. The blade was modeled after a type of Japanese tanto knife known as osoraku, and combines the best of modern and ancient techniques and materials – all fit for a contemporary samurai.
Danaher, a student of martial artist Renzo Gracie, is a lead instructor at Gracie’s New York jiujitsu academy and has coached various UFC personalities such as Georges St. Pierre.
Walter introduces the osoraku tanto. It has a long, thin but sweeping tip, a short bevel, and a secondary ridge. The version he’ll be making is one that can easily be stored in a pack and used as the need arises. He says it’s a fairly tricky knife from a variety of perspectives and is one of the most interesting ones he’s done on YouTube.
There are some lessons here, particularly with respect to grinding. Walter says he’s starting production on a new line of blades, and will be using this knife as sort of a working prototype for a blade he’ll be producing.
He uses 1095 high carbon steel for the job, as it is as close as it can get to Japanese smith’s materials long ago. He’ll be developing a hamon on this knife, a characteristic feature of the traditional Japanese blade that is sometime incorrectly called the temper line. His stock is fairly thick to support the length of the tip and the overall design.
Walter draws the design onto the steel and drills holes on what will be the handle. He uses black micarta for the handle scales. He puts tape on the bottom of the blade before he runs it on the grinder to keep it from getting scratched. He uses the grinders to cut out the basic shape of the knife, including its curves. He recommends using simple curves by angling the steel on the grinder. He also gives tips on how to rig a homemade grinding wheel using sandpaper and a rotating machine.
He cuts out the design for the handle then runs the pieces on the grinder to shape them. Then he grinds the bevels, marking them beforehand. Walter says this takes a lot of skill and patience, as the osoraku shape is unique – it has two distinct sections on its blade.
He uses the traditional Japanese method of heat-treating the blade, known as differential hardening. This hardens the blade but keeps the spine soft. He adds a unique hamon to the knife, making it a one-of-a-kind piece for its owner.