Inspired largely by the brilliant WIP thread by @Blank Blades. I enjoy following, but also an in depth geometry PM convo I have with a friend and a couple requests, I’ve decided to start my own little WIP thread. I’ll be journaling some projects, probably go on a few neurotic rants, and generally just be giving myself a space to get my jumbled notes and thoughts down for my own future reference.
I will start with capturing what’s been my most intense set of grinding work to date. With help from a friend and very generous collector, I was able to purchase this knife, something that’d been on my list for awhile. To put it mildly, this was one of the worse grinds I’ve seen on a premium knife in my time. There were multiple significant over grinds in the middle of the blade, inconsistent hollow grinding on the wide bevel, and unacceptable thickness at the “shinogi” above the heel. Together, the result is a grind that performs poorly and is impossible to maintain. Those reasons alone are significant enough to warrant a regrind in my book, but this blade, being made with scarce togo steel and the highly figured iron Tanaka uses for that steel, deserves a proper kasumi finish as well I think.
This before video hints at the extent of the problem following the blade’s first introduction to stones.
There was, sadly, insufficient material in many places to form the angle separation necessary to maintain a clean shinogi (at least without sacrificing very significant height). Therefore, I decided a convex regrind was the best option. Because of the hollow bevels, low spots, etc. and also my preference for asymmetric grinds, I ended up ended up on settling for something right hand biased. The final goal is geometry fully set and then polished on bench stones.
I started by using a small rotary water wheel to blow out the excess material at the shinogi. After some bulk removal, I switch to bench stones to complete the grinding work. I started by working the blade distally to even out the surface and establish the rough shape of the new grind. Just as the shoulder was wider than the spine with the original grind, the widest part of the blade remains below the spine now. It would be fair to describe the grind as walkschliff - the thickest material being below the spine and more defined convexity towards the heel with flatter geometry towards the tip. The left side is flatter, though still convex, while the right side maintained a bit more heft. Overall the blade is still over 4mm thick coming out of the handle and tapers linearly down to well under 1mm towards the tip.
I found this image from my perpendicular grinding informative. There are three primary angles the blade is ground out: 1) the angle from the spine down to the thickest part of the blade, 2) the transition point where the primary bevel is established, & 3) the final primary angle(s) into the edge. For angle of attack (3), the angle is relatively constant from the heel through the flatter area and you see, due to the taper of the blade, the transition between (2) and (3) lower dramatically as you move towards the tip. As the blade starts to curve towards the tip, I dramatically reduced the angle of attack to create a more acute geometry and lasery tip. The visual trick of a “bulge” in the middle of the blade has been observed before and dubbed, in enlightened circles, the “Kato potato.”
Once the distal surface was evened out, I switched to working perpendicular to the edge and blended everything together - fully eliminating localized high spots and creating an even surface edge to spine. I then followed up with a 45* angle to further blend in the grind and make sure everything was nicely evened out. I repeated this three directional pattern (0*, 90*, 45*) at 400 grit as well. 17g and who knows how many hours later, I am left with a blade that has the geometry fully set on hard bench stones and is ready for subsequent polishing, also on bench stones. By this point, I have also rounded and polished the choil and spine. This is the blade after 400 grit.
All in all, I’m very happy with how this grind turned out. It had great rigidity for a lightweight blade, a good mix of separation and release, and an edge geometry that is both high performing (yes, it very much nail flexes) and robust feeling. Overall, the blade did loose a little over a mm of height and about as much in length, but generally I think the dimensions were well preserved. I’ve altered existing grinds before, but always stayed within the boundaries of the makers intent. This is my first time treating a blade as a glorified blank and, while painful, I’m glad I crossed that bridge.
I will start with capturing what’s been my most intense set of grinding work to date. With help from a friend and very generous collector, I was able to purchase this knife, something that’d been on my list for awhile. To put it mildly, this was one of the worse grinds I’ve seen on a premium knife in my time. There were multiple significant over grinds in the middle of the blade, inconsistent hollow grinding on the wide bevel, and unacceptable thickness at the “shinogi” above the heel. Together, the result is a grind that performs poorly and is impossible to maintain. Those reasons alone are significant enough to warrant a regrind in my book, but this blade, being made with scarce togo steel and the highly figured iron Tanaka uses for that steel, deserves a proper kasumi finish as well I think.
This before video hints at the extent of the problem following the blade’s first introduction to stones.
There was, sadly, insufficient material in many places to form the angle separation necessary to maintain a clean shinogi (at least without sacrificing very significant height). Therefore, I decided a convex regrind was the best option. Because of the hollow bevels, low spots, etc. and also my preference for asymmetric grinds, I ended up ended up on settling for something right hand biased. The final goal is geometry fully set and then polished on bench stones.
I started by using a small rotary water wheel to blow out the excess material at the shinogi. After some bulk removal, I switch to bench stones to complete the grinding work. I started by working the blade distally to even out the surface and establish the rough shape of the new grind. Just as the shoulder was wider than the spine with the original grind, the widest part of the blade remains below the spine now. It would be fair to describe the grind as walkschliff - the thickest material being below the spine and more defined convexity towards the heel with flatter geometry towards the tip. The left side is flatter, though still convex, while the right side maintained a bit more heft. Overall the blade is still over 4mm thick coming out of the handle and tapers linearly down to well under 1mm towards the tip.
I found this image from my perpendicular grinding informative. There are three primary angles the blade is ground out: 1) the angle from the spine down to the thickest part of the blade, 2) the transition point where the primary bevel is established, & 3) the final primary angle(s) into the edge. For angle of attack (3), the angle is relatively constant from the heel through the flatter area and you see, due to the taper of the blade, the transition between (2) and (3) lower dramatically as you move towards the tip. As the blade starts to curve towards the tip, I dramatically reduced the angle of attack to create a more acute geometry and lasery tip. The visual trick of a “bulge” in the middle of the blade has been observed before and dubbed, in enlightened circles, the “Kato potato.”
Once the distal surface was evened out, I switched to working perpendicular to the edge and blended everything together - fully eliminating localized high spots and creating an even surface edge to spine. I then followed up with a 45* angle to further blend in the grind and make sure everything was nicely evened out. I repeated this three directional pattern (0*, 90*, 45*) at 400 grit as well. 17g and who knows how many hours later, I am left with a blade that has the geometry fully set on hard bench stones and is ready for subsequent polishing, also on bench stones. By this point, I have also rounded and polished the choil and spine. This is the blade after 400 grit.
All in all, I’m very happy with how this grind turned out. It had great rigidity for a lightweight blade, a good mix of separation and release, and an edge geometry that is both high performing (yes, it very much nail flexes) and robust feeling. Overall, the blade did loose a little over a mm of height and about as much in length, but generally I think the dimensions were well preserved. I’ve altered existing grinds before, but always stayed within the boundaries of the makers intent. This is my first time treating a blade as a glorified blank and, while painful, I’m glad I crossed that bridge.
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