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I concur with John. Heavy convex grinding can also do that, and require a lot of shoulder thinng before getting to the apex.

It seems that both use the anticorrosion properties of carboxylic acids. The Honerite adds a nondescript amine, that can also have anticorrision property and create a protective film.

I totally understand what you say about the edge producing less drag and requiring less effort during the cut. That's not quite being "stronger" though, and the bevel is thinner...

As the article referenced by 3D Anvil says :

little comparative testing has been done between two otherwise identical knives of equal edge angle with "V" and convex edges to provide substantive evidence for any sort of improvement in edge retention. If there is one it's simply that for equal amounts of force applied to each blade the thinner convex one will be able to cut deeper, and thus cut more material for equal energy expenditure, but the actual sharpness of the edge (or the thickness of the apex on the terminal "edge" bevel) will be affected about the same since it has the same edge angle and degree of wear resistance.

Here is a link to one of his videos, in which he propounds a theory in support of the superior toughness of a convex edge.

https://www.youtube.com/watch?v=XA5AM2Lb0iY&ab_channel=virtuovice

Gord

Well, that's an .... interesting theory. Mixing aerodynamics and structural physics in an innovative way, at least. Do you guys know of any research that would support the underlying assumption that for an equal apex angle, the convex edge is stronger (in terms of edge retention, I guess ?) than the straight edge ?

To be clear, and whatever the answer to the previous question, I find this theory highly suspicious. The fact that vegetable pressure crushing the bevel is the failure mode of the edge is IMHO cuckoo bananas. Unless we're talking hollow knives, but I don't think I have any...

Do you have more information on the troublesome knives (sharpening angle, steel quality, maybe a pic of the edge ) ?

As cbwx34 mentioned, it may be you're sharpening the sides and honing the dull edge...

It may also be a very soft steel, maybe with too acute an angle, and the edge gets rolled when honing.

Keep in mind also that you will indeed have deep scratch marks for as long as the diamonds are not broken in. And even after that, although it won't matter for eventual sharpness.

In my experience, the Composite wheel tends to work faster but leave an edge surface with more scratches than the PA-70...

Nice. My usual projection distance is 145 to 150mm because of rather high blades. So it should do. Thanks for the information, the niew jigs don't seem available in France yet, but I'll keep looking.

Cheers,

Nick.

Thanks for the information and the pics. The change in diameter that you mention means we can probably use it safely along with the older jigs without too much of an error. What was the height of the knife blade with which you had a 140mm projection distance ?

Bar to stone measurements does not work for me to the level of sharpness I want.

Sir,

For the sake of the experiment, do you think you could share BESS scores on the same knife sharpened with your old measurements, and the exact ones derived from Andrew's method ?

Cheers,

Nick.

I do not understand "notoriously difficult to measure, even for the most skilled".

I think the OP's point was taht it is difficult to measurz the constants that allow for precise determination of desired top of USB/top of casing distance.

I would tend to agree with you both : the constants mentioned in quite a few calculators are difficult to measure properly. Measuring consistently from top of usb to top of casing is also quite difficult, at least for me. Measuring to the convex surface that is the top of the wheel (with kenjig or calipers) makes it easier to estimate you're measuring from the desired spot with a more-than-adequate accuracy. And does not require said constants.

I'd say it has to be a thick knife if the convexity is to be noticeable.

By noticeable, I mean "having an effect on the cutting action". A x° apex on a convex edge will tend to have less metal "behind the edge" than the equivalent x° apex on a concave edge. The latter could hinder cutting deeply through dense material. So I'd say everything between a hunting/bushcraft  knife and an axe.

I'm not sure why the "meat knife" they refer to in the video about the new knife jigs would be enhanced by the convex edge...

It indeed makes for measurements that are much easier to make.

Still, I am not sure why one would prefer taking three measurements (both measurements shown here plus the one at sharpening time) compared to only one from USB to top of wheel...

CB, will Tormek discontinue the SVM jigs? I have no idea;

If I'm not mistaken, I think they already refer to them as "the old jigs"...

Maybe the fixed projection of the KJ jigs won't be so bad after all.

It's probably not that bad given the additional stop, but it will require resetting USB between each knife, whereas I did 6 knives last weekend (SG, FVB honing) without a single reset.

Well it's just over so here are my 2 cents (And no, I won't comment on using the AngleMaster when demonstrating a jig engineered to fit thick, heavily tapered knives ^^ ) :

It seems a well-built piece of hardware that indeeds does it's self-centering job. The clamping method doesn't seem overly fussy, and the design inspires confidence.

The projection length is now fixed, the upside of which is that the bloody handle won't turn while sharpening.

However, I really am a bit worried by the convexing method : should the blade "catch" on the wheel, as happened to me twice when I was not pushing down strongly enough on the handle, I fear for the blade and the stone... and me. Anyway, I think it only matters for thick knives where the concavity would have a noticeable effect, and among these I only sharpen cleavers (which won't mind being concave) or traditional japanese blades (which I don't sharpen on Tormek).

Cheers !