next steps on project (knife)

[noj]

Background .. It's an Iron clad Wat that needed a tune-up to be useful. My first goal was to make the useful part be for the kitchen. If it's good/fun polishing practice, that's nice, but it had a lot of warts, so not required. It came so think behind the edge that it almost wedged in a ripe tomato. The blade road had a lot of wobbly surfaces, including a major overgrind at the heel (both sides), the belly (left side 1" from tip), the tip (right side), and a stray hammer mark (right belly). I detected no bending of the blade before or after my work.

I ground out most of the nasty stuff, focusing on getting thinner behind the edge, and getting close to removing the wobbles, and the hammer mark. The overgrinds are reduced due to thinning, but one I am not sure what to do with. Specifically, I was keeping the blade road pretty flat (from tip to heel), and couldn't reach the heel on the right side. I know I can get there by changing the geometry, but that feels like fixing an overgrind by overgrind-ing. Or maybe not. Advise welcome. Picture below. "L" shaped magic marker to show the stone misses it entirely (unless I lift the tip or spine, which I haven't).

Work done so far: grits 200, 400, 1000. Finer grits so I could see what was done more clearly - in areas other than the heel.

 

[noj]

I'd ideally like to reach the heel, but maybe just light sandpaper (for appearance), and sharpen? Other ideas welcome.

I tested it on a fat carrot without sharpening. No cracks or wedging, and I think I left enough convexity for food release.

If you noticed a tiny black line along the entire edge, it's magic marker, to check thinning progress.

 

[ethompson]

What’s it like on the other side at the heel?

This is a very common place (along with the tip) to see over grinds. Can be very annoying to deal with as sometimes these low spots are rather deep. I recall spending a few hours on iron clad Wat I did last year chasing out those last low spots at the heel.

The common mistake here is to either change angle at the heel forcing that area into contact with the stone or to overwork that small area causing the shinogi to rise massively just at the heel. Always remember with low spots the right way to handle it is to abrade the high spots along the full length of the blade down to the level of the low spot. You should never work directly over the problem areas but to the high sides of it and be mindful of blending in your work as you go. Easy to create a low section of the grind or ugly shinogi if you just grind away in one spot chasing out a small hole.

Sometimes it’s not worth chasing out and some paper and finger-stones can blend enough to be satisfactory. Adding in some extra convexity, at the expensive of height, can also make it easier to hit the whole blade in situations like this.

 

[noj]

What’s it like on the other side at the heel?

This is a very common place (along with the tip) to see over grinds. Can be very annoying to deal with as sometimes these low spots are rather deep. I recall spending a few hours on iron clad Wat I did last year chasing out those last low spots at the heel.

The common mistake here is to either change angle at the heel forcing that area into contact with the stone or to overwork that small area causing the shinogi to rise massively just at the heel. Always remember with low spots the right way to handle it is to abrade the high spots along the full length of the blade down to the level of the low spot. You should never work directly over the problem areas but to the high sides of it and be mindful of blending in your work as you go. Easy to create a low section of the grind or ugly shinogi if you just grind away in one spot chasing out a small hole.

Sometimes it’s not worth chasing out and some paper and finger-stones can blend enough to be satisfactory. Adding in some extra convexity, at the expensive of height, can also make it easier to hit the whole blade in situations like this.

Thanks for the reply, and details. I have tried to be careful of not working directly over the problem spots - and there were several. That might be counter-intuitive if you haven't thought through what's happening;-)

I am not sure I am ready to grind that spot out. It seems deep. Changing the convexity at this point might be tricky for me. A lot of my work so far has been reducing convexity because it was so thick behind the edge. There's a lot of curvature to the bevel edge lengthwise (no flat spots). There is also an overgrind in height at the heel. It's a lot of geometry to be changing, at least for me.

Right now, I took some very fine sandpaper to it, then rubbed it briefly on an Aizu. It's not prepped for a polish, but hid some of the effect if you don't look too close. I might just sharpen it and make potato salad, unless there are other ideas.

 

[ethompson]

Patina hides all, putting it to use seems like a great idea!

 

[noj]

What’s it like on the other side at the heel?

This is a very common place (along with the tip) to see over grinds. Can be very annoying to deal with as sometimes these low spots are rather deep. I recall spending a few hours on iron clad Wat I did last year chasing out those last low spots at the heel.

The common mistake here is to either change angle at the heel forcing that area into contact with the stone or to overwork that small area causing the shinogi to rise massively just at the heel. Always remember with low spots the right way to handle it is to abrade the high spots along the full length of the blade down to the level of the low spot. You should never work directly over the problem areas but to the high sides of it and be mindful of blending in your work as you go. Easy to create a low section of the grind or ugly shinogi if you just grind away in one spot chasing out a small hole.

Sometimes it’s not worth chasing out and some paper and finger-stones can blend enough to be satisfactory. Adding in some extra convexity, at the expensive of height, can also make it easier to hit the whole blade in situations like this.

Oops, I forgot to answer your first question - the other side.

The other side has a lot of exposed core. Not my doing either. It also had a big gouge - looked like a grinding wheel caught the heel. I was able to reach most of the blade road on the stone. However, there's a big hole in the middle of the heel, and another low spot at the edge. Can take pics if needed.

On the other side (what I posted about originally) there is little exposed core, despite the overgrind. It seems like the core isn't perfectly straight there. I don't see any bends or twists now to account for it. Maybe it was bent/twisted before they maker did their work?

 

[noj]

I am looking for additional advise before doing more work. I have more photos, observations, and (crude) measurements.

The knife has a lot of profile curvature (as in you could rock-chip with it, if so inclined). The curvature becomes more pronounced near the heel, so much so, that it's "hard" to hit the heel when sharpening. Maybe more that I don't want to risk removing more metal there than "hard" to do. So far, I have avoided sharpening and thinning the heel, other than what I mentioned above. I am thinking it might be good to maintain a curved profile (since that's how it was made). I could see it being easier to work with if the curvature was more evenly distributed, but I don't want dead-flat spots. Adding in some extra convexity, at the expensive of height, and maintaining a good profile sounds complex, given what I am starting with. I envision it would be easy to create a large flat area at the heel.

Some rough measurements: @BTE/~1mm = 0.4mm, @5mm = 0.9mm. and @10mm = 2 mm. So, it's pretty fat, pretty flat with some convexity/thickness BTE. One exception is in the belly closer to the tip - you can even see the profile curvature is less there. I avoided the area as best I could while thinning because I felt a burr, while the remaining edge had magic marker.

Not a big deal, but the "overgrind" at the tip is more like it hit the grinder by accident. It's a small area, but a sudden bevel at like 30 degrees cut into it. I can't really sharpen the side with the "overgrind" without over-overgrinding.

Pictures follow.

 

[noj]

Profile curvature:

 

[noj]

Heel overgrinds. The RHS is as bad as originally depicted (with the big "L" magic marker). All I did was smooth things a little with a finer stone.

 

[noj]

Tip. There was originally already more core exposed at the tip on this side. I did quite a bit of work here, and on both sides, to maintain the straightness (side to side).

 

[ethompson]

Personally, I'd suggest using the knife is for some time. Use and sharpen it enough that it eventually needs a thinning and then tackle your remaining problem spots at the tip and heel. That way you get use out of the mm of steel at the edge that will need to go to enable you to hit those areas without blowing out your shinogi totally at the tip and heel.

Basically you need to cut in a relief bevel at a slightly steeper angle than the bevel as a whole.

Then you need to pick an angle that neither hits the edge or the shinogi and start working that angle

At this stag don't get greedy and just keep at that until you eventually reach up to your shinogi and edge.

These images are exaggerated to make the angle changes dramatic enough to be significant for viewing, but the idea is right.

At the heel and tip you have an area that is slightly hollow / overground behind the edge. You need to remove enough material from the bottom to make that hollow a moot point (doesn't mean raising the edge above those spots entirely, usually no more than 25% of the height is all that's needed. This way you don't have to dramatically alter the shinogi and grind as a whole to chase out that last spot.

 

[noj]

Personally, I'd suggest using the knife is for some time. Use and sharpen it enough that it eventually needs a thinning and then tackle your remaining problem spots at the tip and heel. That way you get use out of the mm of steel at the edge that will need to go to enable you to hit those areas without blowing out your shinogi totally at the tip and heel.

Basically you need to cut in a relief bevel at a slightly steeper angle than the bevel as a whole.
View attachment 316968
Then you need to pick an angle that neither hits the edge or the shinogi and start working that angle
View attachment 316969
At this stag don't get greedy and just keep at that until you eventually reach up to your shinogi and edge.
View attachment 316970

These images are exaggerated to make the angle changes dramatic enough to be significant for viewing, but the idea is right.

At the heel and tip you have an area that is slightly hollow / overground behind the edge. You need to remove enough material from the bottom to make that hollow a moot point (doesn't mean raising the edge above those spots entirely, usually no more than 25% of the height is all that's needed. This way you don't have to dramatically alter the shinogi and grind as a whole to chase out that last spot.

Thanks for the reply and diagrams; very helpful. I will have to try this when it comes time. I like the fact that you have two reference areas (edge/shinogi) where grinding isn't happening to guide things.

Can you please clarify what you meant about "25% of the height"? What I think you meant is if the overgrind is affecting the vertical height (as in my example at the heel), and if I guess (choosing a number for simplicity) that the heel is 1mm too high, that you meant to cut in a relief bevel removing 0.25 mm in total height. Plus, I would guess stopping the relief bevel near problem spots like the heel in my case. Or maybe you meant something else? ;-) I am not sure what it might mean if it isn't affecting vertical height, like the tip, or some knives that merely get too thin (blade width) near the heel or elsewhere.

 

[ethompson]

Sure, what I meant is that you will need to loose some height to make the low spot reachable by a flat stone and able to blend into the existing grind above the edge. If your stubborn low spot is 1mm high and you don’t want to push up the shinogi any more, you will probably need to take 0.25 height off the whole blade to generate sufficient relief sometimes it’s less, rarely more.

 

[noj]

Sure, what I meant is that you will need to loose some height to make the low spot reachable by a flat stone and able to blend into the existing grind above the edge. If your stubborn low spot is 1mm high and you don’t want to push up the shinogi any more, you will probably need to take 0.25 height off the whole blade to generate sufficient relief sometimes it’s less, rarely more.

OK, that's very different from my assumption, if I understand you correctly. It sounds like the low spot measurement is from a flat stone to the (worst) spot not reached by the flat stone (ie from blade road to stone, and not a dip in the blade height like I said).

If that is the case, that height is a small number, but apparently not a small amount of work! In the photo that follows, I hold the edge to the "stone" (Atoma) a few inches above the heel, and "measured" a gap enough to slide newspaper under, or about 0.1 mm. That would correspond to a relief bevel of 0.2 * 0.1 = 0.002 mm, which sounds like next to nothing.

The newspaper is that white thing at the heel. I slid it under *after* pressing the edge down to the backside of the Atoma. The paper slid further that just barely making it, but you couldn't slide a second sheet. The paper was about 0.075 mm, so made a guess at 40% more or 0.1 mm.

But maybe I am measuring something that isn't what you meant, or not! ;-)

 

[ethompson]

Alas, less rosy picture than that.

Sorry the for the confusion - when I say height above I mean as measured from edge to spine more or less.

 

[noj]

Alas, less rosy picture than that.

Sorry the for the confusion - when I say height above I mean as measured from edge to spine more or less.

Got it, thanks; that's what I thought originally.

Will hive it a bit more use before I do major surgery. It still likes to wedge more than I like. I am not sure yet if it's just the blade thickness, or the 0.4 mm BTE, but I can play with that a little without over-overgrinding the bad spots.

Thanks again!

 

[noj]

Some more guidance welcome.

As far are being able to use the knife in the kitchen (ie not just for polishing) I am not liking it, at a minimum because of thickness behind the edge. It's a heavy blade, so I was thinking of shooting for 0.2 mm (vs the ~0.4 mm now). After many hours grinding on 200 grit, I am not sure I see much measurable difference. I am not sure what I need to change here. The stone cuts the cladding rapidly, but on the core it's apparently slow. There is a lot of convexity near the edge. It was there to start with, but difficult for me to change. I tried to use the technique depicted in the diagrams (above). I used a magic magic marker below the shinogi, so I could check that I wasn't wobbling in that direction; I missed in one spot on the flatter (left side), but corrected it. I also used a magic maker along the edge to check progress there; both for uniformity along the length as well as not wobbling (not raising the spine too much). Things looked pretty good from the magic marker, but I never erased the original (shiny) edge bevel - yet. The original edge bevel is often impossible to see unless I stop and dry the knife. Annoyingly, it still feels like I didn't make much progress on behind the edge thickness - measured by caliper and just a lot of convexity there.

If anyone was wondering why I tried to progress using the technique depicted in the diagrams (above), I did so because the convexity near the edge was close to a relief bevel. I realize that description includes some extra metal to be removed.

I also noticed it was hard to sharpen when I was done. Maybe this is typical after so much work on a course stone. I did work the blade road with a progression (after 200): 400, 1000 (3000 once) before sharpening. It feels like there's damage to the edge that has to be removed. I can raise a burr easily, but too easily, even with a light touch - feels like weakened steel. I am sure I can "fix" it by setting the bevel on a courser stone (ie 400 vs 800). Wondering if there is a way to avoid the problem, or it's just typical.

 

[noj]

Bump.

If the question requires something else (for me to explain, etc.) to be answered, or already fully answered elsewhere, please advise.

Thanks!

 

[noj]

If it matters, I am not diverging from what @ethompson suggested (using for a while first). But, to use it, I think I need it to wedge less, and cut better. I think likely the 0.4 mm BTE (with heavy convexity there) is the primary cause of the problem. If it matters, the 200 grit stone is diamond (no not an Atoma), so it should cut blue 2 without much issue. Not sure what else to add.

 

[ethompson]

It can take a frustrating amount of time to make meaningful progress when dealing with hard steel. I used up the majority of a pink brick on a single knife taking 25ish grams off a blue 2 honyaki once. Hours and hours...

When new, most Watanabe / Toyama I've handled have nail flex at the edge, does your example? If not, then you probably just need to keep thinning behind the edge. If so probably time to do a more in depth troubleshooting.

FWIW, I've never calipered a knife I've been working on so sadly I can't offer a mm target for you.

 

[noj]

It can take a frustrating amount of time to make meaningful progress when dealing with hard steel. I used up the majority of a pink brick on a single knife taking 25ish grams off a blue 2 honyaki once. Hours and hours...

When new, most Watanabe / Toyama I've handled have nail flex at the edge, does your example? If not, then you probably just need to keep thinning behind the edge. If so probably time to do a more in depth troubleshooting.

FWIW, I've never calipered a knife I've been working on so sadly I can't offer a mm target for you.

Thanks for the reply and comments.

I didn't caliper it at first. But, then it pretty much wedged in a ripe tomato. It was beyond *not* nail flexing. The whole blade road had a lot of convexity (not a bad thing). The convexity accelerates toward the edge, leaving it very thick. All that said, it didn't cut well.

One think that caught my eye, and makes it more time consuming, is the core steel seems unexpectedly thick.

How far do you think I might go with the 200 grit? So far, I stopped even though there is a trace of the old edge bevel, and not raising a burr, only to discover the 400 grit doesn't seem do much (other than remove 200 scratches). I have been through this a couple times too. I guess just keep at it until that edge bevel is 100% gone.

 

[refcast]

I thinned a KU iron clad wat gyuto that was super heavy and thick, too. I would recommend raising a burr at a low angle, and then raise -- or almost raise -- another burr at a low angle, and keep on thinning in that manner. It was basically unusable when it was stock, or a double bevel deba. I did this on the diamond 400 bbb, but a shapton glass 500 or cerax 320 would have worked for me too, I've used those before to good effect

Photos from @banzai_burrito

 

[noj]

I thinned a KU iron clad wat gyuto that was super heavy and thick, too. I would recommend raising a burr at a low angle, and then raise -- or almost raise -- another burr at a low angle, and keep on thinning in that manner. It was basically unusable when it was stock, or a double bevel deba. I did this on the diamond 400 bbb, but a shapton glass 500 or cerax 320 would have worked for me too, I've used those before to good effect

Photos from @banzai_burrito

Thanks for all that. Looks a lot like mine.

When you said " I would recommend raising a burr at a low angle, and then raise -- or almost raise -- another burr at a low angle, and keep on thinning in that manner", did you mean raise a burr at a low angle, and then raise -- or almost raise a burr, a slightly larger angle? That would of course generate a gentile convexity.

I am currently using a diamond 200 grit, so hoping that should be effective, without getting too course.

What's going on in the photos with the ragged edges? Guessing that after thinning, but before sharpening.

I am guessing the tip didn't come that way. Did you grind it that way because the distal taper was still very thick at the tip. Looks like a lot of work there.

 

[refcast]

Diamond stones are kinda slow for me . . . I don't like them for bulk thinning they take a long time. They skid on hard steel, so that's why I like the cerax 320 for hard steel, it's a soft stone and lots of fresh abrasive. For honyaki that's what I used, since the gesshin 220 and shapton 500 were too hard, uneven scratches or way too slow

For raising a burr, i did mean what I wrote, but for example, raise a burr at 15 degrees, then sharpen at 10 degrees until a burr forms or gets close to forming. The "shoulder" of the edge bevel will start to disappear or look really really faint, which helps thinness behind the edge.

The ragged edge are microchips from use, due to thinning the edge too much, so the angle had to be raised slightly.

Yeah the tip didn't come that way. It's difficult to grind distal taper only at the tip because it's easy to reprofile the tip. I had to reprofile the spine and edge at the tip.

 

[noj]

Diamond stones are kinda slow for me . . . I don't like them for bulk thinning they take a long time. They skid on hard steel, so that's why I like the cerax 320 for hard steel, it's a soft stone and lots of fresh abrasive. For honyaki that's what I used, since the gesshin 220 and shapton 500 were too hard, uneven scratches or way too slow

For raising a burr, i did mean what I wrote, but for example, raise a burr at 15 degrees, then sharpen at 10 degrees until a burr forms or gets close to forming. The "shoulder" of the edge bevel will start to disappear or look really really faint, which helps thinness behind the edge.

The ragged edge are microchips from use, due to thinning the edge too much, so the angle had to be raised slightly.

Yeah the tip didn't come that way. It's difficult to grind distal taper only at the tip because it's easy to reprofile the tip. I had to reprofile the spine and edge at the tip.

For course stones, I have a shapton 120 and 320 (don't know what the 220 is like).

The shapton 120 is kind of useless for me. It burnishes after 3 minutes, and then it's 30 minutes of messing around and cleaning up to resurface. It doesn't release grit on any steel, unless I get out my cold chisel. I know others have different experience, maybe I got a lemon. I use it as a flattening stone now.

I have a Gesshin 220. I am not sure what you meant by being hard. Mine is crazy muddy, and dishes noticeably after just a couple passes. It feels like it would be easy to scratch up places you don't want. I'd say I spend 1/3 of my time flattening it.

I have a shapton 320. I haven't spent a lot of time with it. It releases a lot of sandy feeling grit.

I have a king 300, which actually is hard, but difficult to resurface when it clogs (or dishes). The working surface crazed, but I don't feel the lines.

Not sure how the Cerax 320 compares. Only one way to find out;-)

I know there is at least one other thread on this topic, but the consensus seemed to be course stones all suck on one way or another, just have to pick the right one for the job at hand.

Thanks for clarifying what you meant about the thinning method. I have been trying what @ethompson depicted (diagrams above). I wasn't trying for a burr, or any reference angle there, and instead watching the magic marker under the shinogi and along the edge (plus scratch pattern).

 

[ethompson]

I know there is at least one other thread on this topic, but the consensus seemed to be course stones all suck on one way or another, just have to pick the right one for the job at hand.

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.

 

[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.

With the intermediate angle technique, what leaves me a little uneasy is how much my angle could be wobbling. The magic marker, and reflections on the blade road makes me think I am doing well. The only worrying sign, which may be nothing more than an indication I just haven't reached the edge properly yet, is a lot of convexity and course scratches left in the last 2-3 mm near the edge. The fact that I can see a shiny edge bevel still, kind of reinforces that. Despite trying to be quite careful about grinding evenly, there are two places that are close to zero: at the heel (due to maker's overgrind) and I am mostly avoiding, and the belly near the tip. Right now, I avoid those spots, and lighten pressure as I approach them.

Thanks for the tips.

 

[ethompson]

People aren't CNC machines, there will always be a little wobble. What you're seeing is equally likely just some inconsistency in thickness behind the edge at different areas.

the belly near the tip.

this area is particularly easy to over-abrade, definitely important to make sure that doesn't happen along the way or you'll end up with a foil edge.

 

[noj]

One interesting bit (for people that do measurements), is the fact that the blade road is 2 mm at 10 mm from the edge. That means if you ground it dead flat, it would be 0.2 mm at 1 mm from the edge. I am not going to try making it concave, or dramatically raise the shinogi, so that probably gives me some perspective on how TBE is reasonable for a blade like this. I think 0.4 mm is too big, but attempting 0.2 mm might be a bad idea. You would have to remove all convexity, and that isn't even possible unless I get the CNC upgrade for my wrist and elbow.

 

[refcast]

The gesshin 220 is indeed muddy on soft iron, or when abrading lots of surface area, and it does dish pretty fast. But sometimes it skids for me on hard steel.

Wobble is fine . . .functional as long as you aren't hitting the edge excessively and reprofiling, even then, the effect is a change in height at that place, which you could measure with soft jaw calipers. Functionally, I'm fine with wobble is edge geometry as long as the knife cuts through food how I like. If precise and thin don't possible, then less precise and thin is preferable, since it's more functional.

Check with fingers for thinness from shinogi to edge, and of course the magic marker or edge glinting. The edge bevel should start to disappear with thinning there -- this is the critical step to making a silent effortless cutter. The formation of a foil edge or burr is the indication to stop abrading there.


Check with fingers for thinness from shinogi to edge, and of course the magic marker or edge glinting. The edge bevel should start to disappear with thinning there -- this is the critical step to making a silent effortless cutter. The formation of a fool edge or burr is the indication to stop abrading there,