Advice needed on sharpening this knife

[Royale]

A customer recently handed me a few knives for sharpening. Among the 5 knives (all Anolon brand), 3 of them have deep grind marks along the entire length (I'm going to guess it was from a bench grinder)

What I've done so far for the chef knife in question:
- Polished the entire blade to lighten scratches and to reduce the visible impact of previous grinding.

- Reprofiled the blade with the SG-250, and reduced the full bolster's width/length to match the blade heel. (The knife was banana shaped, with two knife bellies on the blade.)

- Sharpened with the DC-250 & DF-250 at 15DPS, honed with LA-220.

My question:
How would you sharpen a chef knife with a behind edge thickness of approx. 0.5mm? (No error, it's 0.5mm) I've tried and the secondary bevel is approx. 0.8-0.9mm. Would you consider a secondary bevel so narrow to be "complete" or "sharpened"?

Attached image is before sharpening.

[Sir Amwell]

Hi Royale.
I don't entirely understand your question.
But looking at the photo of the knife before sharpening, here's a suggestion on how to proceed.
First grind the bolster down a bit so you can re profile the knife and get rid of the 'smile'.
Then re grind an edge to your 15 degrees per side and hone accordingly to get a sharp, deburred edge.
Only consider 'prettying' up the knife ( polishing, correcting old grind marks etc) if you have checked with the customer if that's what they want to do in terms of the process and agreement of the extra cost to achieve this?
Then state the knife is in it's obvious they aren't too concerned with aesthetics and  a good working edge is all that's required?

[Royale]

Good point, I asked about how to sharpen, but the focus of the question was not exactly aligned with what I asked.

Part one of question:
Seeking advice on how other Tormek users would sharpen a knife with an extremely thin blade (0.5mm behind edge thickness)

Part two of question:
Would a <1mm secondary bevel width be considered acceptable? (I typically aim for 1-2mm bevel width, in conjunction with the sharpening angle)

This knife is already sharpened at 15 DPS, but the secondary bevel is <1mm wide. So I'm just looking for advice if this is commonly done, or generally considered too narrow.

[tgbto]

I don't think there's an absolute answer to this question. It will mostly depend on what steel the blade is made of.

First of all, the bevel height is not an issue per se :

• The more obtuse the angle, the smaller the bevel is. So a 10dps bevel might look higher but will probably be weaker than a 15dps bevel with standard steels
• Many japanese knives (called sujihikis/sujis/lasers) come very sharp out of the box, with barely a visible bevel because the blade is so thin, and no robustness issues. But they are not made of the same steel as Walmart 3-for-20-bucks kitchen knives, and they will hold a 12 dps angle without an afterthought.

In your case, you're in a very different position as - IIUC - the blade is thin because of prior abuse on a bench grinder. I would consider it the same way I'd consider a knive with half-inch-deep knicks along the blade : damaged beyond repair.
Assuming you're willing to invest the time and effort required to reprofile the blade to where it might perform adequately, you will have removed so much steel that the knife will look awkward, with a bulky handle, a weird bolster, a stumpy blade and either scars from the bench grinder, or a much higher thickness behind the edge.

That being said : you've sharpened it to 15 dps, don't worry about bevel height, that's as good as it can get. If it holds the edge well enough, well done ! If not, then repurpose it as a paperweight.

[Royale]

Many thanks for the responses.

I'm already done sharpening the chef knife, and the edge meets my standard of sharpness.

I think I was more curious about what kind of "standards" professional sharpeners work towards, especially when adding uninformed customers into the equation.

Regarding the bevel width, it's just my working theory that if the bevel width is too narrow, then the knife would have more difficulty slicing softer food (like meat) because before the bevel can start the cut, the primary bevel would be trying to wedge itself into the food. If the bevel width was too wide, then it becomes more vulnerable to rolling over/folding. So it's just based on observations from customer knives, my own knives, and brand new knives in stores, that I try to work towards a 1-2mm bevel width.

[tgbto]

I'm not 100% sure your intuition matches what actually happens at the edge.

What happens at the edge is a local phenomenon : Whether the edge is prone to rolling/folding or not depends on the material and the edge angle.
Even a .1mm high bevel is still orders of magnitude bigger than the small elementary deformations that happen when an edge rolls or not.
So changing bevel height will not modify the robustness of the edge. You can have a look at the excellent Science of Sharp blog to get precise measurements.

On the contrary, I can direct you to a bunch of traditional japanese knives who have like a 20+mm high bevel, but the edge will never roll.

As for whether a smaller bevel will make the knife wedge itself into the food, remember the primary bevel is more acute than the edge bevel. So if it indeed has a discernible effect, it is the other way around : the higher the bevel, the more you have to wedge into the food. I attached a drawing of the same blade sharpened at the same angle, but the right one has been ground to get a higher bevel. It gets intuitive which one will put more strain on the carrot ^^.

In my book, the lower the bevel the better, because you get lower sharpening time and amount of metal removed. So you push back the time when the knife needs to be thinned.

Hope this helps !

Nick.

[Royale]

Totally agree with you Nick.

I think a bit of background to this "theory", is that I'm still working on a framework to categorise my sharpening services pricing for my business, as well as streamlining workflows.

Almost all my customer knives have required repairs of different extents, and I was tired of doing these repairs without getting properly paid.

So I developed a framework (that included estimated bevel height) so that I could consistently move customers towards the appropriately priced service tier, to be fairly paid.

So when receiving knives, I measure the behind-edge-thickness, estimate the bevel width, and let them know what the final product will look like. Most of them gauge the quality of service based on the appearance of the knife (strange, I know) I still find it odd how my sharpening business really picked up after I got a bench polisher.

So, for this knife in conversation, I told the customer beforehand that the recommended sharpening angle range (15-20 DPS) would produce a bevel of 1mm width or less, and it would be hardly noticeable. And if she was agreeable with it, then I would proceed with work.

I actively try to avoid getting into disputes with uninformed customers who receive their knives post sharpening, and ask me why almost nothing was done, because they didn't notice any significant difference. (When handing over knives, I typically do a paper cut test in front of them, before they make payment. Using my PT50A test results just goes over their heads, but they can recognise a paper cut test)

So thinking back, my question was more of dealing with customers and what standard of work was deemed "acceptable", in a commercial sharpening context.