Somewhat Interesting / Concerning Observation

I have read and noticed something odd concerning sharpening kitchen knives. There are a few mentions on the net of a small portion of the blade just before the heel of a knife that seems to be a "weak" spot. Weak in the fact that it seem to form a hollow spot on the blade. This area will after time, not make contact with a cutting surface (board et al...).

Why is this? What can be done to prevent it? Is this true with all knives or have I just come across "unlucky" specimens. I have also read it is more prone on knives with bolsters but these J knives have no bolster.

My birthday Doi has this and I have noticed this on several other knives; very mild on these knives but apparent after sharpening. I would assume this would be the technique of the craftsman on the wheels. Maybe the craftsman inadvertently lessens pressure as the heel leaves the wheel. This is on single bevels mostly though I have not seen it on shigs.

Seth said:

My birthday Doi has this and I have noticed this on several other knives; very mild on these knives but apparent after sharpening. I would assume this would be the technique of the craftsman on the wheels. Maybe the craftsman inadvertently lessens pressure as the heel leaves the wheel. This is on single bevels mostly though I have not seen it on shigs.

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wow that is surprising on a Doi... and I have read it is common on double bevel knives. Haven't really read about it on single bevels. With a sujihiki or yanagiba it shouldn't really matter much but with a gyuto or petty, santoku et al... that is another story.

Wide-bevel knives and thin knives show this problem pretty often. It is from grinding, but I'm curious what techniques in grinding lead to a greater proclivity to overgrind near the heel.

XooMG said:

Wide-bevel knives and thin knives show this problem pretty often. It is from grinding, but I'm curious what techniques in grinding lead to a greater proclivity to overgrind near the heel.

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yes that is what I would like to know as well

I would imagine that if the grinder grinds from heel to tip, it could result from a slight hesitation after putting the blade to the wheel.

In the case of knives with bolsters, it's the product of not relieving the heel of the bolster with sharpening.

Can someone post a pic. I'm not sure if I understand.

The portion of the blade marked seems to wear faster than the rest of the knife when sharpening. It is not exactly the same spot, nor is this to "scale" but this is just the general idea.

It may be the area gets first contacted to the waterwheel , as far as I know Shigefusa uses drawknife to shape the bevels , any possible low spots would be most likely eliminated that way compared to Doi's


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more often than not, when i see this, its due to poor user sharpening, not a knife defect. Most high and low spots you see on wide bevels and single bevels will easily work out before causing any problems with blade shape. Even on knives that dont feature wide bevels or double bevels, the high and low spots that i see (and they are always there) dont cause any problems with the shapes of knives.

I don't think it is a defect, but rather an issue that arises when sharpening. I know I have read somewhere that this area should not have a burr formed when sharpening (not sure how that is possible) and the issue will not arise until after many many years. Here is a shot from a vintage knife.

Ha ha, for that knife with finger guard, it is in the way of sharpening. The very finger guard has to be ground down to allow full sharpening of the heel.

schanop said:

Ha ha, for that knife with finger guard, it is in the way of sharpening. The very finger guard has to be ground down to allow full sharpening of the heel.

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yes but I have seen the same thing on knives with no fingerguard

I would bet if everyone looked at their knives they would see quite a few examples

JBroida said:

more often than not, when i see this, its due to poor user sharpening, not a knife defect. Most high and low spots you see on wide bevels and single bevels will easily work out before causing any problems with blade shape. Even on knives that dont feature wide bevels or double bevels, the high and low spots that i see (and they are always there) dont cause any problems with the shapes of knives.

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Agreed. While I have seen some cheaper knives with genuine holes in the edge straight out of the box, which were the obvious result of poor grinding, many people seem to expect too much. High and low spots are inevitable, and it would be unreasonable (and uneconomical) to expect every knife to have them smoothed out by the makers. In the case of user-introduced holes in the edge, I've seen many people spend too much time at the heel of the knife, due to starting there and working from heel, to tip, back to the heel.

Could be the habit of ignoring the middle, or applying initial pressure in front of the heel, as opposed to on the heel itself.

I assumed we were talking about out-of-box defects, of which I've come across several by makers like Asai, Zakuri, and Teruyasu Fujiwara. My Carters and some other knives have some unevenness to the kireba but it doesn't affect the edge.

XooMG said:

Could be the habit of ignoring the middle, or applying initial pressure in front of the heel, as opposed to on the heel itself.

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That too. Like at the tip, people are hesitant to put their finger right on the point.

dmccurtis said:

I would imagine that if the grinder grinds from heel to tip, it could result from a slight hesitation after putting the blade to the wheel.

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This is exactly right. I've sharpened and thinned many knives on a belt grinder, and the first few junk knives I did for practice showed this effect. You tend to put the knife on the belt at the heel and THEN start moving it, so it spends a tiny bit more time at the heel on the belt. With the speed of the belt, that's all it takes. I've since learned to adjust pressure to compensate for this---and I sharpen my good knives on j-nats. :biggrin:

That looks like effect fr. full heel bolster knives. A lot of sharpeners neglect the heel, all of the heel must be on the stone to maintain good knife geometry. Comes from moving knife on the stone with small part of heel hanging off edge of stone.

The heel area gets undersharpened. Perhaps because it's often thicker.

That heel gap happens because of poor understanding of the mechanics of sharpening. Caused by pressuring the knife onto the stone by using the handle instead of the three fingers on top of the stone, thus creating a high pressure point over a curved area. Meaning a blade bent slightly not the curve of the edge, similar to a smiling razor.

I've only got a few knives, but I've seen that unsharpened area on several. Seems to be a "safety" item -- leave the knives dull where people get a fingertip under the heel!

Seriously, I've had more than one fairly decent knife blade left very fat there, obviously not intended to be sharp. Sometimes the edge will be left fat, other times it's ground back from the rest of the edge.

This makes the blade difficult to sharpen, especially when the bolster is left very wide. I grind them down to at least a decent edge. If the area is thick, it really has to be ground down if you want a good edge more than half way back on the blade.

Peter

I have started to sharpen the back area in sectional sequences rather than try to sharpen the knife entirely in long broad sweeping strokes over the stone. Doing this has allowed me to make good contact with the board.

Could it be caused by too agressive steeling? I have seen people apply much force during steeling, and if your steeling motion is from heel to tip (knife) and handle to tip (on the steel), much more force can be applied at the heel than at the tip. This because you start with your hands close together and then work your way towards the tip of both the knife and the steel - much more difficult to apply much force once you're at the tip. My brother's knife was severly worn at the heel for this reason.

I have one knife that came out of the box this way. Took me a while to realize what was the matter, felt much better after I ground the high spot at the very corner of the heel away.

When holding the blade 45% to stone with poor technique the heel will drift off the stone causing the area in front to dish over time with same mistake. Most high heels on knives with out bolsters are because of this.

I just noticed this on my 10-inch Kramer carbon chef's knife. It's very minor, maybe a couple sheets of paper in depth. The knife is four years old and I've only sharpened it a few times, but I am ashamed to say, after one attempt at hand sharpening with a water stone, I got an Edge Pro. I try very hard to take off the minimum amount of steel, but I strongly suspect this comes from my incompetence. I'm sure Bob Kramer can fix it, not that it interferes with the knife's cutting ability, but I may send it back for a tune up.