R&D in the shop

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.

We've also been doing some work on some different compound grinds and think we have a winner for us. This is a knife utilizing the grind though I can't capture it well in a picture. It is a form of S-grind and we like the spine taper interaction with the hollow grind for release. The hollow is present for 2/3 the blade length moving to a very thin full-flat/light convex tip. We will be doing many more with essentially this construction.





We are finishing a set of 4 tester gyutos in a similar profile to this that each have different grinds. We are testing a very heavy spine and strong distal taper tall-bevel grind, two S-grind variants, and a form of convex a little different than our usual. They will be going out to our testers as a group in next few weeks hopefully. A asymmetric two-stage suji is also being tested currently to see how that grind performs. The gyutos are made of different steels, both recycled and bought, and two are one steel with heat treatments that have different emphases. The test is blind and I'm very interested to hear what shakes out.

~Luke

That's cool it reminds me a little of the masakage yuki series if they were all fat chicks and these were models. The traditional usuba stands out as being perfect. So rustic, something I don't see a lot of on single bevels.

great post. my what lucky testers you have...
hope you dont forget to update us with how the testing turns out. also love the traditional blades. while i mainly use yangi or fugubiki your blades have a great style to them. seemingly a lot of western makers dont spend a lot of time with these shapes and its understandable considering the market is smaller and there are plenty of japanese options but its nice to see you guys bucking the trend.

Looking good. Hard to tell from pics but are these dead flat edges? Have found most good usubas to have a slight upsweep towards tip....

jimbob said:

Looking good. Hard to tell from pics but are these dead flat edges? Have found most good usubas to have a slight upsweep towards tip....

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Interesting! They are currently flat, but they haven't been sharpened yet and could be tweaked for some slight curve very easily. The ones at Korin had been very nearly flat in my memory, but I have seen some elsewhere that had some very very slight curve. I suppose it makes sense- just like the flat on a gyuto you don't want it fully flat.

dough said:

great post. my what lucky testers you have...
hope you dont forget to update us with how the testing turns out. also love the traditional blades. while i mainly use yangi or fugubiki your blades have a great style to them. seemingly a lot of western makers dont spend a lot of time with these shapes and its understandable considering the market is smaller and there are plenty of japanese options but its nice to see you guys bucking the trend.

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Will-do for sure. Yanagi are on the list to try. We've done a few but they were customs that were a bit non-traditional and I'd like to get closer to the style. We're playing with these more to expand our knowledge and experience with the breadth of culinary knives in general and because we're getting occasional requests for them. It's always fun to have a challenge, but I doubt the big 3 will become standard builds for us for the reasons you stated.

AMAZING!!! I use a traditional usuba daily at work and would be honored to do some testing of your recent works. :cool2:

Cheflarge, that sounds great! I'll send you a PM here in a second.

We were working on some knives utilizing the compound grind we have been playing with. These are both flat/light convex on the backs and have this on the front. This grind does not steer and we've done it on both sides, but we prefer doing it on the face only as the smooth blade surface on the back is more comfortable on your guide hand. The best part about this grind is that it is flat ground behind the edge which gets it a little thinner than a convex, yet it releases really well. The gyuto was requested to have some forge finish on the spine and choil by the customer, but it also has a strong distal taper that is slightly compound. The tip-ward half of the knife thins rapidly in the taper.

Thes are a 190mm santoku and a 238mm funyaki gyuto. Both are 52100 at 64 HRC. We glued up the handles today so I'll post some pictures of the finished pieces soon. The pictures were taken with the light exaggerating/highlighting the grind as much as possible for clarity. In hand it doesn't look so drastic.









The black speck on this one is dust or something.

~Luke

BloodrootLS said:

We've also been doing some work on some different compound grinds and think we have a winner for us. This is a knife utilizing the grind though I can't capture it well in a picture. It is a form of S-grind and we like the spine taper interaction with the hollow grind for release. The hollow is present for 2/3 the blade length moving to a very thin full-flat/light convex tip. We will be doing many more with essentially this construction.

We are finishing a set of 4 tester gyutos in a similar profile to this that each have different grinds. We are testing a very heavy spine and strong distal taper tall-bevel grind, two S-grind variants, and a form of convex a little different than our usual. They will be going out to our testers as a group in next few weeks hopefully. A asymmetric two-stage suji is also being tested currently to see how that grind performs. The gyutos are made of different steels, both recycled and bought, and two are one steel with heat treatments that have different emphases. The test is blind and I'm very interested to hear what shakes out.

~Luke

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Choil shot of the S grind? :whistling:

Very nice looking and interesting, on the new grinds. Looks almost like a modified single bevel. :cool2:

Here are some finished piece and choil shots, as promised and requested. . .

chiffonodd said:

Choil shot of the S grind? :whistling:

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That knife is off to the customer, but I just added some choil shots of knives with the same grind. Thanks!

Here are the gyutos going out for testing. We're using them for a few weeks, then they will head out.

A convexing (two stage) variant with a pretty flat profile. This one has a very heavy spine with a compound taper that goes into a very fine tip.


S-Grind variant 1, less convexity than variant 2


S-Grind variant 2


Very thin nearly flat grind


Full-convex


~Luke

Gorgeous profiles Luke. I like the look of the first one with some of the scale still visible. Their all quite like lovey.

lus1:

ya i agree they all look lovely. the first one reminds me of a shape mr carter might make. i also like the handle on the last one... i know most dont prefer slender handles but i do. what is going on with that handle... it is just the figure of the wood or is it burned or something else all together?

dough said:

ya i agree they all look lovely. the first one reminds me of a shape mr carter might make. i also like the handle on the last one... i know most dont prefer slender handles but i do. what is going on with that handle... it is just the figure of the wood or is it burned or something else all together?

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The last one is a 190mm- more like a line knife, but even so the handle is on the smaller side. It's figured spalted maple that has been dyed black during stabilization. The ambrosia spalting resisted the dye and the unspalted sections took it much more. Not what we expected when we sent it off, but it turned out pretty interesting.

BloodrootLS said:

Here are the gyutos going out for testing. We're using them for a few weeks, then they will head out.

A convexing (two stage) variant with a pretty flat profile. This one has a very heavy spine with a compound taper that goes into a very fine tip.

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~Luke

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...

man that's just it.

redisburning said:

...

man that's just it.

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Thanks for the encouragement. This is my favorite knife to use out of the bunch, though they're all fun. The geometry and mass distribution on this one really cuts effortlessly and the blade length and flat profile like this is my favorite in use. The blackwood is from old clarinet blanks from a factory in France.

Can't wait to get one of your blade

Man, you guys really make some beautiful knives.