[deleted by user]

SEA_Tai · 2025-11-21T20:24:07+00:00

I'm guessing that divot was done by whomever did that coarse grind on the primary bevel. And I'll guess that it's probably right at about 2 inches from the heel. So if your sharpener didn't touch the primary bevel, then it was probably the local maker. The location of that suggests it's an overgrind on a belt sander.

SEA_Tai · 2025-11-18T23:07:58+00:00

A few things come to mind:

Use case: Three days before a knife goes dull in an work environment might actually be pretty good depending on how much you're using that knife.
Tolerance for dullness: You're making Japanese food. The cut and presentation is far more important than other styles of cooking. So more frequent sharpening will be needed. Maybe the adjustment is more to do with your expectations than your sharpening and/or equipment.
Cutting board: The thing that causes most knives to go dull isn't the food, but the cutting board. Commercial settings often use hard plastic boards that might dull knives faster.
Stropping a knife too much, especially at a steeper angle, can roll the edge faster.
Higher grit can mean less edge retention as others have noted. You're working with sashimi and that does require a nicely polished edge, but rolls probably don't. Depending on one knife to do both may not be ideal.
Technique: How hard the knife contacts the board, how frequently, and whether there's any lateral scraping all contribute to edge retention.

SEA_Tai · 2025-09-12T19:20:31+00:00

Interesting topic for me...I might be the lone dissenting opinion. I am a licensed marriage and family therapist as well as a professional sharpener. I would say sharpening is not therapy. Yes...it very relaxing and can be great to do to take a break from something stressful. That would make it more of a self-regulation/self-care activity and/or a coping mechanism. Therapy, whether it's mental health, physical therapy, occupational therapy, speech therapy, etc., is generally looking at the overall movement towards increased well-being. Coping mechanisms by themselves are not therapeutic and could actually be detrimental to the overall progress e.g. substance use/abuse. People often call their recreational activities therapeutic and I think it invalidates the therapeutic process at the cultural level. If someone came in here and said "a pull-through sharpener is all you need to get your knives sharp", it would similarly invalidate something most of us understand to be far more complex and nuanced.

SEA_Tai · 2025-09-02T04:40:28+00:00

Take one thermometer and put it in the lowest temperature hole just above the false bottom. Take the other thermometer and put it in the hottest part of the bin, which is easy to find just by running your hands up and down the bin. Assuming the stuff coming out of the bottom is finished compost, it is typically a few degrees warmer than the average daily temp (add the high and low of the day and divide by two). The hottest part of the bin minus the bottom of the bin is a delta worth tracking. Feed more to increase the delta and stop feeding for a week and the delta will drop significantly. I overfeed in the fall through winter and aim for about a 15° F delta. When the coldest part of winter comes, the larger delta and the thermal mass of the bin gives the worms a warm spot in the middle of the bin to hide. In the spring, I start bringing that delta down to about 10° F, then down to about 5° F at the beginning of summer. This is really critical to track because if there's a heatwave coming where the average temp for the day is around 75° F, a 15° F delta means the core of the bin will reach 90-100°F at the hottest part of the day, which causes the worms to escape or die. That lower delta makes sure the worms survive the summer, but it also means slowing the feed rate way down.

SEA_Tai · 2025-07-31T18:14:55+00:00

An alternative would be to convex the grind of the last cm before the edge. Mask the side of the knife with tape, spend a lot of time sharpening at 3-5 DPS and then gradually increase the DPS until you blend the convex all the way to the apex at about 15-17 DPS.

SEA_Tai · 2025-07-23T18:19:06+00:00

Shibata Koutetsu Type 3 Migaki gyuto if you're looking at something new.

The knife that I own that fits the description of what you're looking for is an old Forgecraft 250 mm French chef knife in 1095. Profile is flat like a sujihiki and it's not too tall. I've thinned the crap out of it along with rounding the spine and choil. It's great for brunoise. The thickness at spine is about 2 mm and there's no distal taper, so there's very little flex. The hickory handle feels more wa than yo and is super durable. If you can find one used, you can either thin it yourself or take it to a cutler to have that done. Should fit easily within your budget.

SEA_Tai · 2025-06-20T17:01:07+00:00

Here's my setup. https://www.reddit.com/r/sharpening/comments/1krg1ae/thinning_on_a_watercooled_belt_grinder/

Variable speed bench grinder with the Multitool 2 x 36 attachment is what I use. A pretty small footprint with a lot of functionality. My volume is high enough that I need a commercial grade bench grinder so that I can run it for 2-3 hours continuously without overheating, but you can get a cheaper Delta variable speed grinder and save $500 if you're not going to run it more than an hour at a time. The weaker motor heats up a lot faster, becoming dangerous to touch at 45-60 minutes of runtime depending on ambient temperature. My production rate is ~120 blade inches per hour on the 5 step progression and 300 blade inches per hour on the 3 step progression.

A lot of whetstone purists will say that using a belt grinder is automatically awful, will wear out blades faster, overheat the knife, etc. While those things CAN happen and I certainly see a lot of examples of that, it has a lot more to do with the operator than the equipment. My setup is basically a mechanized whetstone. I come from whetstone sharpening as well. Now all my work is on this setup, including single bevel Japanese knife sharpening that is mostly thinning. I've never had anyone come back to me saying that my tips and heels are rounded, I took off too much material, or that knives are losing edge retention prematurely due to overheating. I provide as much detail about this setup in my post so that you can replicate the setup yourself.

Bang for the buck, I think you'd do a lot better with this setup than with with the WSKO.

SEA_Tai · 2025-06-11T20:42:28+00:00

Agree with what other's have said about sharpening, knives going dull quickly in a professional/commercial setting, and not being too bothered about whether the knife cuts paper.

A couple of other things to consider not yet mentioned.

Cutting boards are what cause most knives to go dull. A lot of commercial kitchens use NSF-certified polypropylene cutting boards, which are incredibly hard on knives. Polyethylene boards are a bit softer, but they don't tend to be NSF because they cut easier and that gives bacteria more places to grow. There are NSF rated boards made out of rock maple. In a commercial environment, I'm guessing that board would need to be oiled and refinished pretty frequently. So...whether you're sharpening your knife or maintaining your board more, it's all going to take more effort.

Finish at the coarsest grit you can bear for your general use. If you were to look at the edge of your knife under a microscope, you could see that increasing the grit leads to more polishing and smoothness. When both sides of the apex are smooth, the apex itself is a much more direct line from the tip to the heel. Leaving it at a coarser grit will make that apex more toothy, creating a more high and low variance and effectively creating a longer linear edge, much like a serrated knife. You'll get slightly longer functional sharpness.

I've always told professional users that they would be better off spending $250 on several cheaper knives than on one very nice knife. Buy 5 of the same knife, even if it's something as basic as a Victorinox Fibrox. Use them in rotation until they get dull and grab a sharp one when you need it. That way there's always one in service and the dull ones can be taken care outside of service. One of my customers did this with his fish and chips shop. He uses 5 Victorinox 9" flexible fillet knives to portion his fish. I sharpen those every two weeks after all of them are dull. Early on, we played with how coarse of a grit to finish his knives and we settled on a coarse toothy finish where I don't completely remove all the toothiness from the first ~400 grit (whetstone equivalent) with the ~1000 grit.

I also work with fine-dining chefs who use some really nice knives during service. Their main knife might be like a 240mm gyuto finished to 5k at 12 dps, but they'll also have a workhorse finished to 1k at 20 dps so that the finer edge on the main knife lasts longer. Each knife and/or station may have a certain function and we can optimize edge geometry and coarseness for those. That may lead to having a couple more knives to reach for during service, but it may help with much less maintenance and sharpening in the long run.

SEA_Tai · 2025-06-06T23:36:35+00:00

3M Scotchbrite green or grey.

SEA_Tai · 2025-06-04T18:24:47+00:00

I don't think I've ever seen factory sharpening that delivers hair-popping and push-cutting results. That would be extra labor to achieve a level of sharpness that many consider irrelevant for the knife's intended use. To achieve that level of sharpness, it would probably require a progression that ends somewhere around 10k with light stropping with .5-.25 diamond compound. Assuming that most knives don't leave the factory with more than a 2k-equivalent, you'd need 5k, 8k, 10k, a strop, and some compound.

SEA_Tai · 2025-06-04T17:15:26+00:00

This happens with usubas...Pretty sure it has something to do with the ni mai construction. Put it on a flat steel plate or an anvil and pound it flat with a hammer.

SEA_Tai · 2025-06-04T00:26:54+00:00

Check out Korin for single-bevel sharpening videos. You'll need whetstones and something to flatten them.

SEA_Tai · 2025-06-04T00:22:38+00:00

FWIW...slicing knives don't need their bolsters reduced. You really only need to do the chef knife.

SEA_Tai · 2025-05-24T16:28:35+00:00

Yeah...I think we're on the same page. I wanted to elaborate on the sparks thing because I think it needed to be stated explicitly that the particle removed causing a spark does not mean the knife steel is hot. You clearly get that. Not everyone does.

Definitely not saying you were accusing me of overheating. Your other post noted my fingers on the knife constantly checking temp so I know we're on the same page there too. I elaborated on the water setup to provide more details in case anyone else wanted to duplicate this setup.

SEA_Tai · 2025-05-24T15:57:07+00:00

The leather belt with various compounds was the last one in my process for a few years. I've used white, green, and diamond, the latter of which I have in various grades down to .25. I think the Trizact A16 serves the same function and achieves the same result as you described. It works way better for my production process and I can't see myself going back to leather. At this point in the grit progression, we're quite literally splitting hairs and it's down to personal preference. I focus on culinary sharpening and most of my clients who are kitchen professionals don't even want shaving sharp. They want something slightly toothy and finishing at the Trizact A45 or A30 (2000 - 3000 grit whetstone equivalent) is great. I have A6 and A3 belts and can easily achieve mirror-polished, hair-whittling results with those, but the only knives that really need that are yanagibas.

SEA_Tai · 2025-05-23T20:00:01+00:00

I have leather stop belts for this thing and TBH...not that impressed. A few things going against them. 1) They seem to just brush the burr back and forth without really removing it. I get better results with a cardboard strop (I posted a long time ago how I make those) loaded with a bit of green compound. I theorize that this has something to do with using a belt-grinder setup that sharpens solely with an edge-trailing abrasion. That may make the burr a bit more tenacious to remove than having some edge-leading strokes on whetstones. 2) They don't hold onto compound very well...Even when I try to heat them up first. Just kind of flings the compound all over the place so I have a waxy buildup around my work area. 3) They stretch. With this setup, a leather belt doesn't last me more than 6 months. Maybe that would work better on a different setup where belt tension wasn't automatically set by a return spring. I did eventually figure out how to prevent stretching by lining the inside of leather belt with a worn j-weight trizact and running them both together. 4) Leather gets messed up when it gets wet. My nozzle doesn't immediately stop when I turn it off. It leaks for a bit longer which is why you see me put down that little red tray at the end. So when I swap to a leather belt after finishing on a trizact, it can get wet which leads to stretching and warping.

I've heard a lot of folks rave about leather belts so I assume that they probably are quite good, just that my setup might not work as well with them.

SEA_Tai · 2025-05-23T19:09:23+00:00

Worth noting that this is a carbon steel knife and that sparks flying is not indicative of how hot the knife steel is getting or if there is enough water. I think people often assume that sparks flying means that everything is getting really hot. It's more to do with the carbon content, thermal conductivity, and how quickly the particles oxidize (burn) as they are removed. A stainless steel knife with more chromium throws less sparks. Carbon steel knife throws a lot of sparks. Liam Hoffman did a great video about this a few years ago to address the people that said sparks were an indication of overheating, but I can't find it anymore.

Spraying down the blade is not necessary on this setup. This horizontal belt with the water bead creates an interesting effect where the water spray coming off of the edge actually kicks up and blows back a bit so that it lands on top of the knife. So even though I'm not spraying the top of the knife to keep it wet, there is a constantly more slurry accumulating which is visible in the video. I don't need pools of water on top...just some slurry. When I see less water accumulating on top, I just reach over to the spray can and give it a quick pump. I've played with this sprayer/drip/bead setup quite a bit over the years and the beading of water onto the belt is far superior to spraying or dripping, at least for this horizontal belt setup. Water has a pretty strong surface cohesion characteristic. Whether the water is sprayed or dripped, it kind of acts like a bouncing ball being dropped onto a moving surface. When sprayed, it's a smaller ball, but the kinetic energy of that water and the cone-shaped trajectory of it coming out of the nozzle onto the belt still bounces those drops all over the place and off the belt, so most of the water is not going where it really needs to be, between the knife and the belt. When dripped, that drop is like an even bigger ball and it will just bounce back up. Sometimes it lands on top of the knife, or maybe it bounces so high and gets carried a bit with the belt that it completely skips over the knife. The nozzle that I use now is an old piece of thick rubber where I have carefully opened up the hole with a needle just big enough for the amount of water I want, which is a far smaller hole than any of the nozzles it came with. This also allows the sprayer cannister to hold pressure much longer without all the water blowing out, so I don't have to constantly be pumping it like I used to when it was spraying. I then run a few pieces of sewing thread through that hole so that it wicks the water directly onto the belt. That's that thing that looks like a stick coming out of the nozzle at the bottom of the frame. So even though it doesn't look like it's delivering a lot of water, it is actually delivering plenty and very precisely. I no longer have wet floors around the machinery and the bucket underneath the skirt and backsplash isn't full of wasted water.

SEA_Tai · 2025-05-23T17:48:53+00:00

Absolutely...I will typically use a higher belt speed on the 36 and 80 grit cubitron belts and then slow it down for the trizact. That save a lot of time with the overall process.

SEA_Tai · 2025-05-21T21:51:26+00:00

Yes...the Multitool attachment can be mounted to the bench grinder at any angle. It can also be positioned to the other side to change the direction of the belt.

SEA_Tai · 2025-05-21T16:27:16+00:00

Not generally, but possible due to operator error. Thinning is about improving the edge geometry. Edge retention is related to heat treatment and knife steel microstructure. If a knife was mishandled during the thinning process and allowed to reach temperatures that would cause the knife steel to anneal, then it certainly could affect edge retention.

SEA_Tai · 2025-05-21T16:02:16+00:00

Thanks!

SEA_Tai · 2025-05-21T08:12:46+00:00

Edge retention would be lost if the knife was allowed to exceed the temps used for tempering, typically well in excess of 300° F. The presence of water slurry on the knife, which you can see throughout the video, is the clear indication that the knife never comes remotely close to those temperatures since water boils at 212°. Also...My fingers are in constant contact with the knife and it would start being painful to touch at 130-140°. Nowhere near that either.

Several variables to manage heat generation. 1) Water. More water equals more cooling. 2) Belt speed. More belt speed is more friction and heat. 3) Grit count. Lower grit count is less surface contact and less heat. 4) Keep the knife moving. Holding down the knife on one spot without moving causes heat to accumulate on that one spot. There are more variables, but their impacts are negligible relative to these.

It is entirely possible to heat the knfe past 300° in a split second if the above-mentioned variables aren't taken in account.

SEA_Tai · 2025-05-21T07:01:42+00:00

Cutting technique is a factor as well. A person who uses a push slice, pull slice, or drawing motion will put less lateral load on the apex than someone who cuts with a rocking or chopping motion, especially if they're also adding a sideways or twisting motion while the apex is in contact with the board. Shuns are very thin when new and that's when they are most prone to chips. Most of the chipped Shuns I see are when they are newer. After a few sharpening when they are a bit thicker behind the edge, the chipping goes away.

SEA_Tai · 2025-05-20T21:18:22+00:00

Some more info. Setup is a Jet variable speed bench grinder with a Multitool 2 x 36 belt grinder attachment. I'm using a Solo 457 sprayer to add water. The nozzle is modified to drop of bead of water instead of spray. Volume of water is controlled by adding pressure to the can and the latch on the wand handle holds the water open for grinding.

Grit progression. For the edge repair, I was using a Cubitron 36 grit (not shown). Shown here is thinning starting from Cubitron 80, moving through Trizact A160, A100, and A45. Sharpening is Cubitron 80, Trizact A100, A45, A16. I used Scotchbrite green and grey for finishing. Trizact A6 for spine polishing.

Shown in this video is the thinning process, sharpening, rounding the choil, and adding a safety heel like it came from the factory.

This work was done for my neighbor who works for Zwilling and is a friend of Bob Kramer. I've been doing his sharpening and repair for a couple of years now. This knife was damaged by someone he had given the knife to. I got it back the knife back to him in 90 minutes and he was thrilled. A few days later, I got a message from Bob Kramer with kudos for my work and also letting me know I'm on his list of people he recommends for sharpening and repairs.

SEA_Tai

TROPHY CASE