# Crazy thoughts about burrs



## DavidPF (Feb 17, 2021)

It seems to me that the only difference between a burr and a knife is that the knife is less likely to bend.

It would be theoretically possible to thin an entire knife so much that it was one 50 mm tall burr from top to bottom. Just like the usual kind of burr, it would be extremely sharp but would collapse under pressure.

I don't know the proper name for it, but clearly every knife has a "critical thickness" - if it becomes thinner than that measurement, it will collapse when used. Sort of the point at which it stops being a knife and starts being a burr.

Do different knives have very different "critical thickness" numbers? Or would they all be about the same?

And ... is all of this BS? If it is, then is it easy to tell me why?


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## ian (Feb 17, 2021)

It’s BS. There’s not a single moment when a knife suddenly stops being able to cut spaghetti squash (which I hear is the measure of a good knife) and immediately crumples when you breathe on it. It’s a curve. As the knife gets thinner, it is more easily damaged. Toughness and hardness of the steel will affect the curve. That’s why fancy J knives can be sharpened at an acute angle but soft steel sharpened at that angle will roll.


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## DavidPF (Feb 17, 2021)

Damn. (in an admiring tone, not a disappointed one.) That is about as elegantly perfect an answer as I could imagine. Thanks!


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## panda (Feb 17, 2021)

panda answer: why even have this thought??


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## DavidPF (Feb 17, 2021)

In that case, why have ANY thought?


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## M1k3 (Feb 18, 2021)

I forget which knife maker, but they made a knife so thin, on accident? , it was foil.


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## McMan (Feb 18, 2021)

M1k3 said:


> I forget which knife maker, but they made a knife so thin, on accident? , it was foil.


Sysco Reynolds. Prices have gone up lately.


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## DavidPF (Feb 18, 2021)

M1k3 said:


> I forget which knife maker, but they made a knife so thin, on accident? , it was foil.


This is real? Or a joke I'm not currently bright enough to get? It would be interesting to see the result.


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## ModRQC (Feb 18, 2021)

Before your hypothetical knife becomes a burr, a few things will happen:

- Too much flexibility for use
- Wedge like crazy
- Breaks about like an exacto knife

But much more importantly than these, their order, or complimentary:

You'd cut your pinching hand right through on any produce harder than it.


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## M1k3 (Feb 21, 2021)

DavidPF said:


> This is real? Or a joke I'm not currently bright enough to get? It would be interesting to see the result.


Not a joke. Unfortunately I can't find the post again.


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## ian (Feb 21, 2021)

DavidPF said:


> This is real? Or a joke I'm not currently bright enough to get? It would be interesting to see the result.



I think both @Kippington and @RDalman have talked about grinding an edge too thin and then having it turn into foil. I’ve done that myself even, and it’s not hard, unfortunately. One problem is that when an edge is thin, it can start to flex under pressure, and it can flex so that the very edge becomes basically parallel to the stone, so even though height of the spine of the knife indicates like a 10 degree angle, the actual sharpening angle at the edge is basically 0, which is bad and will create a foil edge.


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## RDalman (Feb 21, 2021)

ian said:


> I think both @Kippington and @RDalman have talked about grinding an edge too thin and then having it turn into foil. I’ve done that myself even, and it’s not hard, unfortunately. One problem is that when an edge is thin, it can start to flex under pressure, and it can flex so that the very edge becomes basically parallel to the stone, so even though height of the spine of the knife indicates like a 10 degree angle, the actual sharpening angle at the edge is basically 0, which is bad and will create a foil edge.


I pretty much intentionally grind like that, doesnt take much work a 1k-stone to thicken back up, but I do like to send them on the thin side, since we like that around here


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## Kippington (Feb 21, 2021)

DavidPF said:


> It would be theoretically possible to thin an entire knife so much that it was one 50 mm tall burr from top to bottom


Skip all the hard work and simply make a knife out of aluminium foil.



ian said:


> One problem is that when an edge is thin, it can start to flex under pressure, and it can flex so that the very edge becomes basically parallel to the stone, so even though height of the spine of the knife indicates like a 10 degree angle, the actual sharpening angle at the edge is basically 0, which is bad and will create a foil edge.


100% this.


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## M1k3 (Feb 21, 2021)

Kippington said:


> Skip all the hard work and simply make a knife out of aluminium foil.
> 
> 
> 100% this.


Oui Chef! 1 case diced potatoes! Heard!


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## DavidPF (Feb 21, 2021)

Thanks, all of you - I appreciate you taking the time and effort to explain/show it.

That choil shot seems to show that my original thought was not completely insane, just not nearly as fascinating as I made it seem in my own mind.

Plus the fact that every real-world example of it seems to be a mistake or misjudgement.

Or maybe (sort of, not really, but not SO far off) part of a day's work running the large grinding wheel at a razor factory. 

_Curses! Foil again!_


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## LucasFur (Feb 22, 2021)

I have personally seen a 210MM sukenari honyaki with probably 10mm of foil along the edge. Why? ... He wanted to make it a petty ... why? ... i dont know.


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## DavidPF (Feb 22, 2021)

Re. my earlier "razor" comment:

Search the page for "Guillermo" if you don't immediately see a "choil shot" of a razor. (It's a shot from the tip of the razor, not the choil, but you know what I mean.)









Does size really matter?


I just answered a PM regarding 7/8 razors and the lack of blanks for 7/8 thumb notch razors in Solingen. Personally I’d be willing to pay a pretty penny for a 7/8 thumb notch razor made by Aust or Wacker. I like all of my modern 7/8 razors regardless of maker (Aust and Thiers Issard), but...




www.badgerandblade.com


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## cotedupy (Feb 22, 2021)

Another member noted recently that the forums could do with more poetry. Following this post I would like to add that the forums could also do with more random kitchen-knife-based thought experiments. Good work!


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## DavidPF (Feb 22, 2021)

I asked "Is this 'critical thickness'
A thing? Has my brain got a sickness?"
They kindly replied:
"Though your brain isn't fried,
When a knife gets like this, it is yickness."


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