next steps on project (knife)

[refcast]

(Accidentally double posted)

 

[noj]

Yep, everything under 400 grit is flawed in some way. You have to pick which compromises you want to live with - wear rate, precision, cost, speed, etc

To build off @refcast, I'd suggest you just keep going at the intermediate angle until your apex bevel is just a hairline of sharpie. At 500 grit or so I'd try and take that down to zero. so that you're barely raising a burr while at your thinning angle. I don't like to zero out below 400 grit, but 500 is okay.

I think I will pursue this technique, specifically because of the overgrinds.

The technique @refcast mentioned is interesting and appreciated, but perhaps better suited for a knife with less anomalies.

Will report back when I get more metal grinding time;-)

 

[noj]

I am curious about thoughts on "thinning" technique. When I say "thinning", I am referring to both major thinning and removing edge shoulders (not sure if there is a more proper name). Most of what I have read in other threads just describes finger pressure, and very little on angle (raising the spine). With just finger pressure, I have often found it difficult to abrade the core (well - without abrading fingers), and easy to remove cladding where you don't want.

I am not trying to suggest that there is only one way, or start an argument. The two methods described here, thanks to @ethompson and @refcast, are quite different, possibly because they are designed to solve different problems and/or produce different results. Others are of course welcome to reply as well;-)

My best guess was that using the technique @ethompson suggested with the best course for the knife at this time. I say that because I estimate it gives me more control of fixing the various overgrinds, high spots, and inconsistent geometry close to the edge.

That said, I also am curious about "thinning" techniques more generally, not specifically this knife. See above for quote-thinning-unquote.

Thanks to @refcast, I ordered a cerax 320, so we will see how that works.

 

[noj]

Bump.

Comments welcome. Comments from those who replied to other questions are very welcome, but not "expected". Hopefully, others have curiosity in the topics, or suggestions.

The Cerax 320 is coming Tuesday.

 

[noj]

Feedback welcome. I can grind metal away, but can't put it back;-) Got the Cerax 320. Would the glass 500 be a good next stone? I would like the next stone to hide the Cerax 320 scratches, still cut core steel decently, and ideally be able to see if I need to go back to the 320 without going higher in grit.

Please see questions I posted above https://www.kitchenknifeforums.com/threads/next-steps-on-project-knife.71342/page-2#post-1110782

 

[refcast]

I mean the next step is to actually try and thin . . . . If you want a beater knife I can send you one

 

[noj]

I mean the next step is to actually try and thin . . . . If you want a beater knife I can send you one

I got a couple beaters, but thank you for the offer. I may give those a try first.

I was more curious of techniques. The one you suggested involved working from high angle to lower angles. I can imagine the reverse, which may be a bad idea or not I imagine the technique you describe has the advantage of creating a burr at each angle, which gives you a reference (ie when to stop). Maybe the reverse could be useful as a fast way to just knock the shoulders down, or maybe should be avoided. Then @ethompson had an idea that at a minimum was suggested to solve my problem with overgrinds, and may or may not be good for general thinning. Then a lot of people don't have much description of thinning other that put it on a stone, and the work is done under the fingers, and don't suggest anything about angles. Maybe each has it's place - to solve different problems. Maybe some are personal preference - lots of different videos. Maybe some should be avoided. Maybe there are others I haven't thought of.

Anyhow, these are some of the questions that came to mind.

I'll fire up the new Cerax, and see what I think of it.

 

[refcast]

The cerax has a hard outer surface that needs to be abraded away before it starts cutting faster.

I guess I didn't mention different thinning purposes . . .

Some people want to make a wide bevel for polishing, that requires reducing convexing or making concave parts flatter to touch the bench stone.

Some knives wedge at the shoulders mid cut into dense foods -- these benefit from thinning the wide bevel and not necessarily close to the edge. So the thinning angle is the wide bevel angle or slightly more acute (which raises the shinogi more, but both can). The choice is, if you keep the wide bevel angle the same, the knife will get thinner right behind the edge too

Some knives don't even want to enter food easily, these benefit from a lower edge angle or thinning close to the edge -- so the thinning angle is slightly lower than the edge angle.

I find that thinning right behind the edge gets me a better performance result for less time, so that's what I prefer to do first usually.

As for angle vs pressure yeah it gets confusing. There's also stroke angle too . . .parallel, perpendicular or diagonal to the edge. Angle matters the most. Pressure determines scratch depth. The abrading feel is different on iron vs steel, steel will scate and scratch less deep, iron will catch on the stone more readily. Angle of thinning will determine a bit of what feedback you'll get. Thinning on a very convex surface will feel bad and skatey, then as more surface gets in contact, more swarf comes out, thinning feels more pleasant. Usually more shallow scratch depth too.

It's not worth "removing" overgrinds necessarily (bringing down all high spots or even proper height grind spots...). The expense can be time, height of the knife, making it too thin, overworked one spot at the expense of the smoothness and continuity of the grind.

The angle vs pressure . . . I think it's mostly angle that matters. Also diagonal strokes give me the best angle consitinecy and blend throughout the grind if the knife. You can try different ones and observe. Pressure on very thin knives can bend them . . .sometimes recurves can form, especially at the tip and with very coarse stones.

Low pressure leads to shallower scratches and easier deburring, easier to remove scratches on the subsequent stones.

But yeah try both methods and see which works for your purposes. I've had knives for wide bevel polishing before and I didn't enjoy those necessarily, so I care about cutting performance the most, and that comes fastest with reducing the step between the wide bevel and the edge, making that transition smooth.

As for the shapton glass 500, yeah it'll remove the 320 cerax scratches, I've used a 1000 grit cerax before

 

[ethompson]

if you are willing to cover postage each way, I’d take a look at the blade and give you my thoughts. As we’ve all discovered in this thread, pretty challenging to diagnose performance problems from afar when the big picture looks pretty good.

 

[noj]

The cerax has a hard outer surface that needs to be abraded away before it starts cutting faster.

I guess I didn't mention different thinning purposes . . .

Some people want to make a wide bevel for polishing, that requires reducing convexing or making concave parts flatter to touch the bench stone.

Some knives wedge at the shoulders mid cut into dense foods -- these benefit from thinning the wide bevel and not necessarily close to the edge. So the thinning angle is the wide bevel angle or slightly more acute (which raises the shinogi more, but both can). The choice is, if you keep the wide bevel angle the same, the knife will get thinner right behind the edge too

Some knives don't even want to enter food easily, these benefit from a lower edge angle or thinning close to the edge -- so the thinning angle is slightly lower than the edge angle.

I find that thinning right behind the edge gets me a better performance result for less time, so that's what I prefer to do first usually.

As for angle vs pressure yeah it gets confusing. There's also stroke angle too . . .parallel, perpendicular or diagonal to the edge. Angle matters the most. Pressure determines scratch depth. The abrading feel is different on iron vs steel, steel will scate and scratch less deep, iron will catch on the stone more readily. Angle of thinning will determine a bit of what feedback you'll get. Thinning on a very convex surface will feel bad and skatey, then as more surface gets in contact, more swarf comes out, thinning feels more pleasant. Usually more shallow scratch depth too.

It's not worth "removing" overgrinds necessarily (bringing down all high spots or even proper height grind spots...). The expense can be time, height of the knife, making it too thin, overworked one spot at the expense of the smoothness and continuity of the grind.

The angle vs pressure . . . I think it's mostly angle that matters. Also diagonal strokes give me the best angle consitinecy and blend throughout the grind if the knife. You can try different ones and observe. Pressure on very thin knives can bend them . . .sometimes recurves can form, especially at the tip and with very coarse stones.

Low pressure leads to shallower scratches and easier deburring, easier to remove scratches on the subsequent stones.

But yeah try both methods and see which works for your purposes. I've had knives for wide bevel polishing before and I didn't enjoy those necessarily, so I care about cutting performance the most, and that comes fastest with reducing the step between the wide bevel and the edge, making that transition smooth.

As for the shapton glass 500, yeah it'll remove the 320 cerax scratches, I've used a 1000 grit cerax before

Thanks, I'll absorb all this in a bit - too sleepy right now;-) First thing I did was flatten/resurface the stone - pretty typical to have a crust (or maybe it's for marketing). I tried briefly on a stainless steel junk knife. Seems to cut fast, doesn't clog, a bit easy to dish - very friable.

 

[noj]

if you are willing to cover postage each way, I’d take a look at the blade and give you my thoughts. As we’ve all discovered in this thread, pretty challenging to diagnose performance problems from afar when the big picture looks pretty good.

Very generous of you to offer - thank you. If I go that route, I will PM.

 

[KasumiJLA]

I did a big thinning project recently and it took me about 3 sessions before the performance was to my liking. Generally when I work the main bevel it is for the aesthetic finish. But on this project it was purely to practice and achieve exactly the feeling I wanted with the knife.

I started with a big weight loss while keeping the basic geometry. When I thought I'd done enough, I tried the knife. It was obviously way better but not how I would like it to be.

Two days later I tackled the project again. I thinned it out a bit more and decided to move the shinogi line up about 3mm. I also thinned a bit more the section 10mm after the cutting edge. There I said to myself, that's it, it's going to be perfect! I used the knife the same evening and no, still not perfect. I even had a light steering effect to the right, something I didn't have the session before.

Maybe a week later I decided to finish this damn project, again. So I reached out for my calliper and decide to measure a similar profile which performs really well. I was off by not that much, but just enough to have a different experience with the knife.

So I figured I would remove about 40% by working on three separate sections: 10mm, 5mm and finally behind the cutting edge. So here is the result before and after my third thinning session :

	Before	After
Behind the edge	0,30	0,16
5mm	0,72	0,41
10mm	1,29	0,96

I started by thinning the 10mm section focusing only on this region for finger pressure. When I had the desired measurement, I moved on to the 5mm section and so on. In the end I blended the three sections. Blended is a big word because those sections are so close to each other but hey..!

At that point the knife performs way better and I also corrected the steering. By taking the time to measure, rather than going by eye, I realized that it's really the very small details that change everything. Honestly I should work on it again and aiming for maybe 0,08 behind the cutting edge.

In short, it was nice to work purely on geometry rather than preparing a canvas for polishing. It's cool to have an idea in your head and try to make it come true, even if it's sometimes frustrating. I may not provide much of a solution to your problem, but as long as I'm sharing my struggles with this knife, I might as well do it here!

 

[noj]

I did a big thinning project recently and it took me about 3 sessions before the performance was to my liking. Generally when I work the main bevel it is for the aesthetic finish. But on this project it was purely to practice and achieve exactly the feeling I wanted with the knife.

I started with a big weight loss while keeping the basic geometry. When I thought I'd done enough, I tried the knife. It was obviously way better but not how I would like it to be.

Two days later I tackled the project again. I thinned it out a bit more and decided to move the shinogi line up about 3mm. I also thinned a bit more the section 10mm after the cutting edge. There I said to myself, that's it, it's going to be perfect! I used the knife the same evening and no, still not perfect. I even had a light steering effect to the right, something I didn't have the session before.

Maybe a week later I decided to finish this damn project, again. So I reached out for my calliper and decide to measure a similar profile which performs really well. I was off by not that much, but just enough to have a different experience with the knife.

So I figured I would remove about 40% by working on three separate sections: 10mm, 5mm and finally behind the cutting edge. So here is the result before and after my third thinning session :

	Before	After
Behind the edge	0,30	0,16
5mm	0,72	0,41
10mm	1,29	0,96

I started by thinning the 10mm section focusing only on this region for finger pressure. When I had the desired measurement, I moved on to the 5mm section and so on. In the end I blended the three sections. Blended is a big word because those sections are so close to each other but hey..!

At that point the knife performs way better and I also corrected the steering. By taking the time to measure, rather than going by eye, I realized that it's really the very small details that change everything. Honestly I should work on it again and aiming for maybe 0,08 behind the cutting edge.

In short, it was nice to work purely on geometry rather than preparing a canvas for polishing. It's cool to have an idea in your head and try to make it come true, even if it's sometimes frustrating. I may not provide much of a solution to your problem, but as long as I'm sharing my struggles with this knife, I might as well do it here!

View attachment 321574

Thanks for the info and story.

Interesting you started grinding higher (10mm and shinogi) first, and @refcast was doing the opposite, but obviously solving different issues.

One thing that I keep running into is slow metal removal of the core (as in almost can't measure anything). Will have to see if the Cerax helps.

Can you get at the core steel (and near the edge) with finger pressure, or do you have to lift the spine? I don't seem to make any progress with finger pressure, but don't want to make it too convex either. And I like to keep my fingertips;-)

It might be a week or so before I have time for this one again. Here's my choil shot now - after two sessions. Caveat - overgrind at the heel;-)

The out-of-focus bit at the heel is one of the overgrinds.

 

[KasumiJLA]

I have no issue to remove material from the hagane and obviously I try to keep my fingers on the blade to avoid some nasty injury.

When I work near the edge I generally work with the pressure of my thumb and I position myself at an angle so that I am comfortable and as close as possible to the cutting edge but without sticking out so that my thumb rubs on the stone. If that makes sense.

For the heel problem and for geometry in general, @ethompson is really the person I know who knows the subject very well. I've already had problems with heel over grind but the result I got was that the shinogi line really went up too much. Is it the end of the world? Not at all, but visually it's not a perfect job. But it becomes complicated to make up for this production "error". At a certain point I believe that you have to make a decision without compromising the geometry and the use of the knife.

 

[noj]

I have no issue to remove material from the hagane and obviously I try to keep my fingers on the blade to avoid some nasty injury.

When I work near the edge I generally work with the pressure of my thumb and I position myself at an angle so that I am comfortable and as close as possible to the cutting edge but without sticking out so that my thumb rubs on the stone. If that makes sense.

For the heel problem and for geometry in general, @ethompson is really the person I know who knows the subject very well. I've already had problems with heel over grind but the result I got was that the shinogi line really went up too much. Is it the end of the world? Not at all, but visually it's not a perfect job. But it becomes complicated to make up for this production "error". At a certain point I believe that you have to make a decision without compromising the geometry and the use of the knife.

Thanks for some ideas. I haven't tried using my thumb for pressure. I've always used my fingers, mostly in the same pattern as I do while sharpening. My middle finger is a lot longer, and if I am not careful enough .. well;-)

I'll do some more work next week (too busy just now). I think I can do more thinning along the lines @ethompson described because there is still thickness at the edge - in some places. The geometry is getting tricky. The belly near the tip is about zero ground, so must avoid. The heel has overgrind, so must avoid. The tip is tricky because the spine is still very thick, and a few other oddities. Unless I drastically change the shinogi, the best BTE measurement I can expect is (if ground dead flat with no edge bevel) @1mm is 0.9/5 ~ 0.2 mm.

I am not sure I can make better at measurements. To one significant figure, I got @5mm = 0.9mm. and @10mm = 2 mm. I think that tells me I am not measuring accurately, because it implies the "surface is concave"*. If was perfectly flat, you would find 2 x 0.9 = 1.8 at 10 mm, and @10mm > 1.8 implies concave, and @10mm < 1.8 implies convex.

Your measurements give an interesting result also:

before: 2 x .72 = 1.44 and at 10mm 1.29 < 1.44 → convex
after: 2 x .41 = 0.82 and at 10mm 0.96 > 0.82 → concave

My best guess is neither of us ground our knives concave;-) Probably just a tiny measuring error, and both are quite flat overall.

===================
* for you mathematicians and engineers - I am avoiding a lot of technical jargon and precision, but I think it gets my point across better this way