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How to identify grind issues

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mhlee

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From what I've read, grind issues are one of the major and common issues with all knives; overground knives can be more flexible than correctly ground knives, can cause a knife to steer because one side of the knife is ground more than the other, and can cause a knife to not cut smoothly, among other things.

However, I'm not sure what to look for. I have knives that are more flexible than expected, knives where one side of the knife seems to be ground more (the grind seems to go higher than the other side). But, I'm not sure these knives are overground or incorrectly ground.

What are clear markers or things to look for to identify grind issues?

Thanks.
 

tk59

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grind issues:
Point the knife tip toward a window or something that is going to show straight lines when reflected on a flat surface. Look at the reflected lines on either face of the knife. Convex grinds will show some even curvature in the reflection. Flat grinds will show straight lines. Uneven grinds (those with one or more over/under grinds) will show wavy lines. More grind imperfections means more waves. You will also see bends and twists this way but you cannot differentiate between the three without looking at a couple more things.

You can run your fingers carefully on both sides of the knife simultaneously and feel for uneven grind.

You can look at your bevel. If your angle is fairly consistent, an overgrind near the edge will manifest itself as a wave or dip in the bevel. It is common to find overgrinds on the heel of knives, making them appear thinner than they really are.

Bends:
Point the tip of the knife toward your eye with the spine up. If the knife is bent, you will see a wave in the spine.

Twists: Do the same with the edge up. If you see a different bend than the spine, your blade is twisted.

Keep in mind, all knives have imperfections. In fact, I believe minor grind uneveness would probably decrease "sticktion" and improve performance to an extent. Also, fixing may not be the best thing for a knife. Even in straightening a knife, you will cause other small bends or other deformations. There are also imperfections we can't see in the steel and sometimes fixing the bends leads to pretty severe microscopic cracking or even breakage. For most knives, the question should simply be does the knife work the way it should. When I'm paying big money for a knife, I'd want the grind to be pretty damn good but that's just me. I am a knut, after all.
 

tk59

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:happy2:
I was wondering if you were gonna bring that up somehow.
 

Delbert Ealy

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I wonder why this topic comes up today?
(sorry I could not resist, I tried, but I was overcome)
Del
 

Eamon Burke

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If you don't have a hole in the edge, you don't have an overgrind problem. Not yet at least. :sofa:
 

mhlee

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Del:

It actually has nothing to do with either you or Moritaka knives. I don't own one of your knives or a Moritaka.

Actually, it's just something I've been thinking about for a while now, and something that I've been very curious about. I exchanged some e-mails with Tinh recently and we briefly discussed this. I just wanted to learn how to identify grind issues on my own.
 

SpikeC

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I've been really careful to make sure that the blades on the knives that I have been making have as straight a blade as I can make. Today I looked at the Forschners that I have used for the last 20 years, and they are bent! I don't know what this means as a practical matter, butt I guess sometimes it is better to not look? As long as it keeps cutting, anyway!
 

Delbert Ealy

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Del:

It actually has nothing to do with either you or Moritaka knives. I don't own one of your knives or a Moritaka.

Actually, it's just something I've been thinking about for a while now, and something that I've been very curious about. I exchanged some e-mails with Tinh recently and we briefly discussed this. I just wanted to learn how to identify grind issues on my own.
Michael,
Thanks for clarifying, I would love for all the members here be able to recognize potential problems in a knife upon close inspection, maybe even at a glance. Grind issues and even bent blades can be hidden in pictures, but not easily in person. Bent blades have absolutely no excuse, if the blade is not straight, that happened at the time of heat treating and should have been rectified then, they don't warp after just sitting there, especially after tempering. I have had blades warp in heat treat and I fixed them, sometimes warping badly enough that I am required to go through the whole process again. Most of the knives you guys use are so hard that it requires a great deal of force to bend them on purpose, let alone by accident. Some of the knives with softer cladding may be a little more subject to bending or taking a set, but it still takes a lot of force and determination to do.
Twisted blades are more often than not a result of uneven grinding, especially in full flat or full ground, but slightly convexed blades where it is harder to see than on a partially ground blade. It is easy for a person who is strongly right-handed to grind knives with a slight twist to them, especially at the tip. In this way many left-handers have an advantage, because in our right-hand dominant society, they are forced to use their right hands more. I long ago learned this lesson and grind almost as well left-handed as right. I can't swing a hammer as well with my left, but I do grind with both.
Even grinding comes only with practice, there is no other way, you practice until it is correct. I was surprised when Dave first broached the subject of the overgrinds as you have come to know them. They are present in the larger knifemaking community, and are most freqent among new grinders. I was amazed to hear of this occuring in kitchen knives.
Grinding a knife to thin I have already addressed in my subforum.
Specific questions are always welcome.
Thanks,
Del
 

Delbert Ealy

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Jon,
I am speechless(well almost) I have no idea why that should be. Its never happened to me. It should not happen at all, I'll have to think about this. I may PM you later about that subject.
Thanks,
Del
 

geezr

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del... i've seen quite a few knives warp just sitting there... both clad and unclad
another example of the unexpected for me - been reading about this happening to some kitchen knives;
it started with wood expanding, contracting, needing to be stabilized;
then it was some wine need be de-cantered to open-up and become tasty (doing that now for dinner :hungry:)
 

JBroida

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sure

obviously with clad single bevel knives, its different, but with clad double bevel knives, it can often be because the thickness of the cladding is different on each side and causes warping (especially when the steel has not been allowed to rest... whatever that process is called where the internal forces are "tempered" so to speak)

single steel knives are often a result of the steel being improperly heat treated in my experience, so if your heat treat is good, i guess you wont see it too often.
 

Eamon Burke

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With all due respect(which is certainly a lot) to Japan, I have heard tell that traditional Japanese smiths often are not taught to fully understand and respect the annealing process, it's more a heuristic kind of thing, and leads to incomplete or uneven heat treats being more common(though many smiths don't let it past their QC). I've seen pictures of shops that have literally hundreds of knives that rest for months before sale because the steel is still shifting and settling, and late warpage is common enough to warrant the wait.
 

goodchef1

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as far as the "no excuse for the bent blade" thing, does the maker forget to check the straightness of the blade? or is it due to just lack of attention and/or care? I also heard that clad combo steels can warp by just sitting there for awhile, which is why I only get single steel blades now. No experience myself, but I don't want to take any chances with finding about it later in the future. Is it a given for them to warp? or is it the unlucky few who come across this?
 

JBroida

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for what its worth, i've seen this in both japanese and american made knives... heck, even some german and spanish knives
 

El Pescador

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We all know about Daves hate of Moritakas...everyone has a right to their own opinion, including Dave!
 

shankster

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We all know about Daves hate of Moritakas...everyone has a right to their own opinion, including Dave!
You're correct,he has every right to express his opinion,but enough of the Moritaka bashing already.We know how he feels about it,but that's not what the OP asked.It's not fair for someone,even Dave,to paint every single knife ever produced by Moritaka with the same brush.
 

Dave Martell

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Hey guys I'm just joking you know.....well sort of.....it's a joke with truth to it which makes it kind of funny in my eyes but I guess that if you own one of the knives and then it's not so funny but why not have some laughs? They're just knives. :)
 

SpikeC

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You're correct,he has every right to express his opinion,but enough of the Moritaka bashing already.We know how he feels about it,but that's not what the OP asked.It's not fair for someone,even Dave,to paint every single knife ever produced by Moritaka with the same brush.
He has never said such a thing. You are being overly defensive of your favorite product.
 

shankster

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He has never said such a thing. You are being overly defensive of your favorite product.
"if it says Moritaka on the blade :D"
Sure i guess he's kinda joking..kinda

It's not really what Dave says about Moritakas that bothers me so much,he's at least had experience with them,it's when people who may or may not(more than likely not) had any experience with them chime in/jump on the band wagon..so to speak.It's kind of like someone giving a bad review of your favorite restaurant after they've just had dinner there and someone who's never been there says "ya if you say so it must be crap"
Yes I'm overly defensive/sensitive of my Moritakas but that's just who I am.
 

Dave Martell

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From what I've read, grind issues are one of the major and common issues with all knives;

This isn'tt exactly true, yes they're a concern but not in a major or common issue, however, some makers are known to have major & common issues with (over) grinding. This is why I go on about Moritaka so much (versus every other maker) - because they're habitual bad grinding offenders whereas most others do a very good job. There are some exceptions like Aritsugu A-types - they suck grind wise as well. As for non-Japanese (American) knifemakers there's lots of over grinding going on here - 2" wide belts make for 2" wide divots.



...overground knives can be more flexible than correctly ground knives, can cause a knife to steer because one side of the knife is ground more than the other, and can cause a knife to not cut smoothly, among other things.

On flex - it depends because if a knife is over ground in a way as to be too thin then yes it'll be flexible but it's more likely that a knife will be thick and have overground section and be very stiff still.

If the sides are ground uneven then yes the knife can steer. This is very common with many Japanese knives that are purposely designed with uneven grinds from side to side. That's Ok for those knives though since they're purpose built and the user needs to learn proper technique to perform said purpose correctly. I believe most gyutos (even asymmetric ones) are not meant to steer though.



However, I'm not sure what to look for. I have knives that are more flexible than expected, knives where one side of the knife seems to be ground more (the grind seems to go higher than the other side). But, I'm not sure these knives are overground or incorrectly ground.

What are clear markers or things to look for to identify grind issues?

If a knife steers from flex then I'd say it's the wrong knife for the task or maybe just wrong for you.

Japanese knives are all ground asymmetrically - every last one of them so finding them ground uneven from side to side is to be expected. Is the knife ground correctly for the type of knife that it's meant to be - this is the question.

Clear markers for overgrinds are an edge bevel that goes through different thicknesses (along the length) like a roller coaster. A wide (at the heal) bevel that steadily decreases to very thin at the tip is normal but tall and short and tall again are clear indications that the knife has been overground in sections. The thin sections are the overgrinds. I suggest sharpening the knife upon receipt - if the bevel goes all roller coaster like then you just uncorked the maker's cover up. It's easy as hell for a maker to cover up an overgrind (looks great OTB) but it's way easier for you even to uncover it by using a flat stone.

Another clear marker is the low hanging heal or a hole in the edge that shows light under the edge in one spot or where another spot doesn't allow for the edge to make full contact with the cutting board.

I like to not only look at the edge as it rolls along the cutting board but much more accurately assess the board contact from eyeing down the length of the edge with the tip in my left eye (well almost) and cutting edge up. If you look down the belly (using your right eye) you'll see everything clear as day.

You can also go one step further and use an engineers square (straight edge - not a ruler!!!) to find highs and lows on the blade sides. Pay particular attention to the area immediately (1mm) above the edge bevel - this is the zone that'll cause you trouble when sharpening.


Hope this helps you some.

Dave
 
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