BloodrootLS
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David and I are always playing with new ideas and trying new techniques and I thought I'd share them here in a thread, partly for your enjoyment and partly so that you can catch us when we are doing something dumb or give us good advice. . .
So, here lately we've been doing a lot of reading and work with understanding kitchen knives from a functional perspective. One of the areas of knife design that we know the least about and have been exploring are traditional single bevels. We were at Korin a month or so ago and were able to closely observe some examples. We also have been doing a lot of reading on the use and technique associated with those blades. Last week we took some time to explore the usuba, and the week before we built another deba. We've done a few debas in the past but had never made or used an usuba. We made a Kamagata usuba and a traditional usuba and made them from an 1800's 1095 two man bucksaw blade that had an interesting surface from weathering. We made them essentially mizu-honyaki with a brine quench (less distortion than water) from 1440F for full transformation to martensite and maximum hardness, but instead of clay coating the spine we differentially tempered it (our standard practice for our knives. Not important for this style of blade per se since it's thick, but differential tempering leaves the spine as tempered martensite instead of clay coating which generates an unhardened structure (ferrite and cementite in a pearlitic form) that has a much lower strength than the martensite. On thin blades the additional strength lends rigidity and that degree of tempered martensite is even tougher than the pearlite). The blades were tempered to HRC 61, which, through break testing best balanced toughness/brittleness in these geometries for this alloy. The deba is a custom smelt 1080+ that has about 0.6% chromium that we got from a German-built granite cutting sawblade. It's a good workhorse steel that is clean, achieves full hardness (HRC 66-67) and is very tough. We of course oil (Parks 50 quench oil) quenched this steel.
Here are the test pieces we made this week.
So, here lately we've been doing a lot of reading and work with understanding kitchen knives from a functional perspective. One of the areas of knife design that we know the least about and have been exploring are traditional single bevels. We were at Korin a month or so ago and were able to closely observe some examples. We also have been doing a lot of reading on the use and technique associated with those blades. Last week we took some time to explore the usuba, and the week before we built another deba. We've done a few debas in the past but had never made or used an usuba. We made a Kamagata usuba and a traditional usuba and made them from an 1800's 1095 two man bucksaw blade that had an interesting surface from weathering. We made them essentially mizu-honyaki with a brine quench (less distortion than water) from 1440F for full transformation to martensite and maximum hardness, but instead of clay coating the spine we differentially tempered it (our standard practice for our knives. Not important for this style of blade per se since it's thick, but differential tempering leaves the spine as tempered martensite instead of clay coating which generates an unhardened structure (ferrite and cementite in a pearlitic form) that has a much lower strength than the martensite. On thin blades the additional strength lends rigidity and that degree of tempered martensite is even tougher than the pearlite). The blades were tempered to HRC 61, which, through break testing best balanced toughness/brittleness in these geometries for this alloy. The deba is a custom smelt 1080+ that has about 0.6% chromium that we got from a German-built granite cutting sawblade. It's a good workhorse steel that is clean, achieves full hardness (HRC 66-67) and is very tough. We of course oil (Parks 50 quench oil) quenched this steel.
Here are the test pieces we made this week.