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#290125 - 07/31/18 05:54 PM Re: Chef knives [Re: Russ]
dougwalkabout Offline
Crazy Canuck
Carpal Tunnel

Registered: 02/03/07
Posts: 2688
Loc: Alberta, Canada
Originally Posted By: Russ
Belt sander? Isn’t that a little much for a knife post heat treat? Does that have no effect on temper? After years of neglect, I used an old Tri-hone (oil) and brought it back to a fine edge in about 15 minutes. I really don’t think a belt sander is necessary, but that’s just an opinion.


As Phaedrus indicated, it's all about the operator. Light, quick passes are fine so long as the blade never gets uncomfortably warm to the touch. A nearly worn out belt can get you in trouble in that regard. I practiced a lot on beater blades before I was comfortable working on good ones.

A belt sander is not necessary for domestic kitchens. Nor are spendy knives, for that matter. Generally, the best blade for the job is a well-maintained blade. I've been on a quest for years to teach people how to do basic hand grinding and steeling (realignment) so they can get decent performance from the knives they already have.

Since I repair and recondition hundreds of knives a year, a belt sander is just about mandatory. Some of those are literally rounded off, and it takes forever by hand. I still hand-finish good quality blades, though; I haven't got around to buying a buffing wheel.

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#290130 - 08/02/18 02:46 AM Re: Chef knives [Re: dougwalkabout]
EMPnotImplyNuclear Offline
Enthusiast

Registered: 09/10/08
Posts: 322
Originally Posted By: dougwalkabout
dougwalkabout: As Phaedrus indicated, it's all about the operator. Light, quick passes are fine so long as the blade never gets uncomfortably warm to the touch. A nearly worn out belt can get you in trouble in that regard.

Hi,

I've gotten a blade uncomfortably warm to the touch without power equipment, just a dry piece of sandpaper.

The apex of a sharp knife is only ~1 micron thick or 1/1000 millimeter, it doesn't take a lot to burn/overheat


Most factory sharpened knives come burned from the factory. They're sharpened without coolant on beltsanders and buffers.

See
global-knife.com/catra/ test on factory vs hand sharpened edges

Will I feel the edge of my knife overheating from grinding with bare hands? - knivesandstuff https://www.youtube.com/watch?v=vDiBqEDVEZY

Summary: ~2inch strip of knife steel, blowtorch (thousands of degrees hot), 40 seconds later the knife feels warm

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#290131 - 08/02/18 03:20 AM Re: Chef knives [Re: Phaedrus]
EMPnotImplyNuclear Offline
Enthusiast

Registered: 09/10/08
Posts: 322
Originally Posted By: Phaedrus
I'm baffled by the CI reviews of knives. I've had quite a few of the Victorinox Fibrox knives and sharpened perhaps a hundred of them. They will get the job done but edge retention is very poor, at least by the standards of a chef. Good for the price I suppose but a review shouldn't merely identify the cheapest blade that will turn one chunk of food into two chunks! Even an entry level Japanese gyuto like the Tojiro DP absolutely smokes the Vics. You could use the Tojiro for a couple weeks in a restaurant setting without much more than a few licks on a ceramic hone; with the Vic you'd be lucky to have a serviceable edge after a few days. For the home cook that's not as big an issue but there's no comparison between the build quality or fit and finish, either.

Hi,
Overheating knives on a beltsander could easily explain knives going dull after a few days (ignoring plate contacts).
Even a $1 knife will last more than a few days.
Most chefs use a "chef steel" or "butchers steel" to keep the blades cutting for months and months.
This is what you see for sale at restaurant supply one ~$5 knife steeled once a day lasts this professional chef 6 months




Edited by EMPnotImplyNuclear (08/02/18 03:21 AM)

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#290135 - 08/02/18 03:40 AM Re: Chef knives [Re: EMPnotImplyNuclear]
dougwalkabout Offline
Crazy Canuck
Carpal Tunnel

Registered: 02/03/07
Posts: 2688
Loc: Alberta, Canada
I respect what you're saying. And in addition, based on my experience, I respectfully suggest there is more to the picture.

First, I realize I was unclear: it's touching the edge that I was talking about, right as it's coming off the belt. You're absolutely right that if the mass of the blade is hot, the temper has already been messed up -- and the operator is a hack.

I'm not sure that all factory blades are messed up. That hasn't been my experience anyway. Mid-range or better blades usually "bite" properly on contact with hand stones (usually diamond for me) and that indicates that the steel at the edge is effectively the same as the steel in the mass of the blade. It's correct to note, though, that many factory edges are only fair-to-middling at best, and I find there is significant room for improvement.

Some lower-end blades, though, are absolutely temper burned right from the factory. Sometimes it's accidental, but sometimes it's a way of sexing up shoddy steel. I noted this in low-end Gerbers and early "Henckels International" blades out of China. It took me a long time to figure out WTH was going on. It seems that the layer under the extra-hard "burned" layer is tough, grainy, and highly abrasion resistant -- and it doesn't take an edge worth beans. Working through this by hand, to the "meat" of the blade, takes forever (with vigorous cursing). Only a belt sander or wet wheel can peel through it with any reasonable efficiency, after which the steel handles normally (for better or worse).

I still prefer hand sharpening, and especially hand finishing for good quality blades. There's a feedback from the blade that I don't get from the sander. But I think the scratch pattern from the sander is so much more consistent that, with practice, it might give a more durable edge -- respecting the temper, of course.


Edited by dougwalkabout (08/02/18 03:43 AM)

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#290136 - 08/02/18 04:13 AM Re: Chef knives [Re: EMPnotImplyNuclear]
dougwalkabout Offline
Crazy Canuck
Carpal Tunnel

Registered: 02/03/07
Posts: 2688
Loc: Alberta, Canada
I'm not sure you realize it, but the link you posted has Phaedrus as a commenter if you scroll down. Rather like waving a flag in front of a bull? Hope that was not intentional. wink

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#290137 - 08/02/18 02:09 PM Re: Chef knives [Re: Russ]
Russ Online   content
Carpal Tunnel

Registered: 06/02/06
Posts: 4857
Loc: SOCAL
So I like knife steel. I was looking at a brand of knives I hadn’t seen until recently and saw something called MC66 as a steel in one of their knife lines. So I ask myself, “Self, what is MC66??” Drum roll please...

Hitachi MC66 Knife Steel is ZDP-189. I was never too keen on ZDP-189 in an EDC blade, but in a Damascus kitchen knife the ZDP-189/MC66 would be wrapped in other softer steels. Still need to take care with chipping the edge, but that’s always true.

ZDP-189
Quote:
ZDP-189 – Made up of Carbon: 3.00%, Tungsten: 1.50%, Vanadium: .10%, Chromium: 20.00%, Molybdenum: 1.30% ... It is also known as MC66 and is used by Henckels under that alias.

It’s used as the core steel in the Miyabi Black line. Thinking about a 5.5” Santoku. Just thinking... wink

FYI: How To Choose Kitchen Knives Kitchen Knife Steel FAQ Stainless Steels

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#290139 - 08/03/18 12:49 AM Re: Chef knives [Re: dougwalkabout]
EMPnotImplyNuclear Offline
Enthusiast

Registered: 09/10/08
Posts: 322
Originally Posted By: dougwalkabout
I respect what you're saying. And in addition, based on my experience, I respectfully suggest there is more to the picture.

First, I realize I was unclear: it's touching the edge that I was talking about, right as it's coming off the belt. You're absolutely right that if the mass of the blade is hot, the temper has already been messed up -- and the operator is a hack.

Hi,
Well , I also respect what you're saying, there is always more to the picture, its just a matter of degrees wink

How many mm deep does the damage go?
How bad was the damage?

Its kinda like bread , how big is the slice? And what color was it: light toast v. dark toast v. charcoal ?


The apex of the edge is like a 1 micron thick wire ,
it takes very little energy (fraction of 1 joule) to overheat to 2000F.
It can heat up real fast, as in milliseconds (1 second = 1000 milliseconds), and it cools off just as fast.

The video with the blowtorch is like a 5000 times magnification.



Originally Posted By: dougwalkabout
Mid-range or better blades usually "bite" properly on contact with hand stones (usually diamond for me) and that indicates that the steel at the edge is effectively the same as the steel in the mass of the blade.


Not sure exactly what you mean .... but isn't that type of check very coarse ? only detects heavy damage?


Originally Posted By: dougwalkabout
Only a belt sander or wet wheel can peel through it with any reasonable efficiency, after which the steel handles normally (for better or worse).


How many mm of blade width are you talking about?

Cutting into a coarse stone (~200grit) like you're trying to cut it in half removes metal rather quickly.




Originally Posted By: dougwalkabout
I'm not sure that all factory blades are messed up. That hasn't been my experience anyway.


I said "most" and that is only like half of "all" :P Is that statement hype or dry toast?


Dry grinding of all kinds seems "most" common wink and thats bad

https://waikato.researchgateway.ac.nz/handle/10289/10004
http://knifegrinders.com.au/SET/Edge_retention_worsening_by_felt_wheel.pdf

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#290140 - 08/03/18 08:31 AM Re: Chef knives [Re: dougwalkabout]
Phaedrus Offline
Pooh-Bah

Registered: 04/28/10
Posts: 2130
Loc: Great Plains
Originally Posted By: dougwalkabout
I'm not sure you realize it, but the link you posted has Phaedrus as a commenter if you scroll down. Rather like waving a flag in front of a bull? Hope that was not intentional. wink


Hahaha! Just got the chance to revisit this; today was my first day off in about five weeks.

I agree that some factory knives ship with "burnt" edges. I don't think it's common and when I do see it the damage is usually fixable by sharpening the blade a couple times. It's a pretty good rule of thumb that if the edge feels hot while you sharpen you're risking damage to the edge. But while you can overheat an edge with just sandpaper you can also keep an edge cool on powered equipment. Even a very high speed grinder is safe if contact with the belt is kept brief. This is especially true when using fine grits- they're easier to burn the edge with.

I think you'll find that using a grinder like the Kalamazoo with 80 grit Blaze ceramic belts you'll be hard pressed to burn an edge before you've ground the knife down to an ice pick.
_________________________
“You can tell whether a man is clever by his answers. You can tell whether a man is wise by his questions.” Naguib Mahfouz

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#290141 - 08/03/18 08:38 AM Re: Chef knives [Re: EMPnotImplyNuclear]
Phaedrus Offline
Pooh-Bah

Registered: 04/28/10
Posts: 2130
Loc: Great Plains
Originally Posted By: EMPnotImplyNuclear

Hi,
Overheating knives on a beltsander could easily explain knives going dull after a few days (ignoring plate contacts).
Even a $1 knife will last more than a few days.
Most chefs use a "chef steel" or "butchers steel" to keep the blades cutting for months and months.
This is what you see for sale at restaurant supply one ~$5 knife steeled once a day lasts this professional chef 6 months




A hand sharpened Vic will still be dull in a few days. Just for kicks I've sharpened them up to 5k, a level of polish which proved to be a complete waste of time save for the experience gained. Bear in mind that a restaurant cook will make more cuts one shift than most home cooks will make in several months. It's not uncommon to cut a fifty pound bag of onions or a half bushel case of peppers all in one go. Sometimes this is done on various other gear (choppers, etc) but just as often it's done by cook on the lowest rung on the seniority ladder. grin
_________________________
“You can tell whether a man is clever by his answers. You can tell whether a man is wise by his questions.” Naguib Mahfouz

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#290159 - 08/07/18 03:45 PM Re: Chef knives [Re: Phaedrus]
Russ Online   content
Carpal Tunnel

Registered: 06/02/06
Posts: 4857
Loc: SOCAL
What is the best sharpening angle that’s thin enough to dice onions, but tough enough to cut up a whole roast chicken? The Vic Forschner Chef knife was resharpened to 23º per side and it has cut up a whole roast chicken and diced onions.
Is 23º necessary for the chicken? It diced onions okay, but thinner would have been better. What sharpening angle is thin enough for onions and tough enough for chicken bones? TIA

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