Sharpening Methods and their Effects on Heat Treatments

RJPRIP

RJPRIP

Member
Hello World..

This is my first post and its really more of an inquiry. I have bought a Triple - Laminated Stainless steel "Helle". There is information on their main site regarding preferred sharpening methods for their blades. They mentioned something to the affect that sharpening the knife without oil (or water?) would render their heat treatment inefficient! Is this a commonly known fact in the world of knife making?! Or does this depend solely on Helle's steel and tempering process, or is this just a claim? Will sharpening a Tri-Laminate Sandvik steel (or any stainless or high carbon), by hand & on a stone - without a lubricant, have negative effects on a blades heat treatment? Is it possible Helle is dejecting the method of high power & friction sharpening on a grinding wheel?!

- Thanks for reading and responding, RJPRIP
 
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Very good point Frank.. However, I do know that some knife makers initially remove the stock either by hand, power methods or water jet. Some makers cut and grind in edge bevel (s) before they temper the steel.. Ill have to do some more homework I guess!? Thanks for your input.. Apparently this isn't a popular subject.
 
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Sharpening the blade by hand on a stone will not negatively affect the heat treatment,with or with out oil or water.
Sharpening the blade on a belt grinder or some other fast moving grinder COULD affect the heat treatment if you over heated the edge. Using water to keep the edge cool during this operation will prevent overheating and ruining the temper of the edge.
 
Heat treating steel is a known quantity, there aren't many secrets and these folks don't do anything others don't. Many of us grind blades after hardening and when we do its important to keep in mind that the steel can't be overheated. If its overheated, where the temperature goes above the temperature used to draw or temper the blade the hardness will drop. The higher the temperature the more the hardness drops. I do a lot of sharpening on a horizontal disc and use no lubricant; I do place the tip of my little finger directly on the edge so I can feel the heat. Believe me the tip of your little finger is very sensitive to heat and will let you know when the edge is getting warm.

There are people who market their products inferring that their product is special and different from others. It sounds like this is what is taking place here. I can think of no reason for the statement other than wanting to make their blade seem special in some way.
I know people who sharpen blades using a right angle grinder, those get severely overheated.
 
I have heard people make these claims before and think it is paranoia of overheating the edge. I do my initial sharpening on a belt sander dry and have never had a problem. Although I have noticed I get a cleaner cutting edge when I use oil or another kind of lubricant, though this is not because an overheated edge but because the stone stays cleaner throughout the sharpening process, also sharpening without lubricant will ruin some stones.
 
I also grind my bevels after heat treatment of my knives and sharpen on a belt grinder.
Most stainless steels have a last temper in the 400 degree range. I never let the steel get over about 200 degree or the temp of boiling water.
As long as you keep the blade at this temp or less you are in no fear of ruining the heat treatment of the steel. That's with or without oil or water. Grinding or sharpening?

Also I would like to welcome you to KD's.

Laurence

www.rhinoknives.com
 
Believe it or not, sharpening without a wet lube will cause micro-burning to the edge. For most common cutting, it is insignificant, and probably undetectable in general use, but that's why razor blades are wet sharpened by the producers. It will certainly not ruin the overall temper, just right there at the micro level.
 
Interesting thoughts all the way around gentlemen! Thank you for your insight! Nice to meet you Rhino. :)
 
LRB said:
Believe it or not, sharpening without a wet lube will cause micro-burning to the edge. For most common cutting, it is insignificant, and probably undetectable in general use, but that's why razor blades are wet sharpened by the producers. It will certainly not ruin the overall temper, just right there at the micro level.
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LRB,

I am not sure what you are calling Micro-burning at the edge? Is this something you have seen under a Microscope of have other proof of?

Laurence

www.rhinoknives.com
 
I have seen references to it on metallurgy boards, and a few times elsewhere over the years. We are talking microscopic burning I don't consider it to be of great importance unless making or sharpening razors. Any time you are sharpening, you are tearing pieces of steel away. This causes friction, friction causes heat. Years ago I read a mention of this by an old machinist. He said files wear out from burning at the extreme edges of the teeth. I did not think much about it until I saw other references to it.
 
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DrySharp.JPG


Here is a posting that, IMHO, validates the dry grindin/sharpening issue. I believe Kevin Cashen would also subscribe to the valididty of this information. I have also seen ESM (electron scanning microscope) images that clearly show "bluing" at the micron edge from dry sharpening on 8K diamond hones....now if I can just find them.

PZ
 
pabloz said:
View attachment 40023


Here is a posting that, IMHO, validates the dry grindin/sharpening issue. I believe Kevin Cashen would also subscribe to the valididty of this information. I have also seen ESM (electron scanning microscope) images that clearly show "bluing" at the micron edge from dry sharpening on 8K diamond hones....now if I can just find them.

PZ
Click to expand...

I remember reading that a while ago: thank you for posting it pabloz.
 
pabloz said:
View attachment 40023


Here is a posting that, IMHO, validates the dry grindin/sharpening issue. I believe Kevin Cashen would also subscribe to the valididty of this information. I have also seen ESM (electron scanning microscope) images that clearly show "bluing" at the micron edge from dry sharpening on 8K diamond hones....now if I can just find them.

PZ
Click to expand...

PabloZ,
Thanks for posting, I am all for keeping things as cool as possible when working heat treated steel!
I would be interested in seeing those pictures? If you have the circumstances used even better.

I have no doubt that many sharpeners using fixed speed machines at 1800 -3600rpm can torch and blue the edges. I see it on knives and scissors that come into my shop for sharpening and repair.

This statement that hand rubbing a dry block of steel on a 1000 grit piece of sandpaper can make temps reach 2000C, the converter,
if I am doing this correctly, states 2000 degree Celsius = 3632 degree Fahrenheit.
Is incredibly hot?

I sharpen 50-100 knives a day, with no complaints, using my variable speed 2 x 72" on about 20% power and use fresh belts daily. I keep the knife moving and make many light passes. I have looked with 10x loupe and don't see any sign of bluing or tempering colors for lack of a better term?

I wish I had a way to measure accurately the temps reached in my belt sharpening. I may experiment with using a water based cutting fluid on the belts but didn't have good results when I tried this for grinding blades after heat treatment.

Laurence

www.rhinoknives.com
 
I've heard Roman talk about this in person. He's concerned with what he considers "the edge" of a sharp knife.
He defines this as the last 30 microns with the actual edge itself being less than 1 micron across the "blunt"
part. Nothing in this scale is optically visible, even with a microscope. He was showing electron microscope
pictures of edges, with carbides in some steels clearly standing out like large blocks embedded in the edge.
 
Dan Pierson said:
I've heard Roman talk about this in person. He's concerned with what he considers "the edge" of a sharp knife.
He defines this as the last 30 microns with the actual edge itself being less than 1 micron across the "blunt"
part. Nothing in this scale is optically visible, even with a microscope. He was showing electron microscope
pictures of edges, with carbides in some steels clearly standing out like large blocks embedded in the edge.
Click to expand...

Dan,
I believe those were the images I was referencing above. IIRC they clearly showed the "toothy" edge with coloration from the friction generated heat.
Do you have access to those images??? I believe they would clearly make anyone interested in "best practices" of sharpening a believer in wet only after HT.

Laurence,
I am very much a fundamentalist therefore when the science proves the theory I adopt that method. For as long as I can remember, going back to childhood, everyone that ever taught me to sharpen on stones or plates always used oil or water. Being that very high temps can be reached with hand applied speeds it only stands to reason that if the speed is increased by a machine then the temps must go up and the time to reach those temps is shortened as well. It may only be at the nanometer level but it is an unavoidable event unless cooling through liquid conduction is present. In all reality, the end user will probably never feel the difference and the only one who would genuinely know whether or not there is any improvement would be you.

After heat treat, if my blade ever goes back to the grinder I use a trick I learned from Bob Terzuola pictured here:

(used with permission)
Sponge.jpg

I have also used this technique with the Deerfos cushioned belts you use for sharpening.

PZ
 
Pablo, Dan etc...

I have also read and done the techniques from a book at work where the author touts dry sharpening as a improved and better technique and I would have to agree with him on several points. I can post this author and book name tomorrow.

I also agree that science and physics are a constant at least until you get to the quantum level anyway?

This afternoon I sharpen more knives and a few scissors along with ground out two heat treated blades and polished two blades on cork belts with green chrome. all of these process's can produce heat.

There are so many tools in industry from drill bits, chipper blades, Lawnmower blades etc.. that are sharpened dry that my deeper question is at what point does this mirco-burning really effect the performance?

With that said I always do my best to keep things:cool: and will continue to do so. I have a product from Angler that is a water cutting fluid that I tried to use as a aid while grinding but I would get so much build up of crud on the flat platen so quickly that I would have to stop too often to clean things up.

Since I sharpen slack belt, No Platen, Perhaps I can soak a sponge etc with it to keep things :cool: as in the
picture?

I will keep everyone posted.

Laurence

www.westsidesharpening.com
 
pabloz said:
Dan,
I believe those were the images I was referencing above. IIRC they clearly showed the "toothy" edge with coloration from the friction generated heat.
Do you have access to those images??? I believe they would clearly make anyone interested in "best practices" of sharpening a believer in wet only after HT.
Click to expand...

I don't have the images, he used them in a presentation at Ashokan a couple of years ago. However I suspect that all of them and more are available in his book, which is something like a doctoral thesis with knife edges as the topic.

Messerklingen und Stahl ("Knife blades and steel")
Roman Landes (2006)
ISBN: 978-3-938711-04-0

Unfortunately it's in German...
 
Dan Pierson said:
I don't have the images, he used them in a presentation at Ashokan a couple of years ago. However I suspect that all of them and more are available in his book, which is something like a doctoral thesis with knife edges as the topic.

Messerklingen und Stahl ("Knife blades and steel")
Roman Landes (2006)


ISBN: 978-3-938711-04-0

Unfortunately it's in German...
Click to expand...

Dan,
It's in German? Won't do me any good!

I thought about this important corresponding test this morning while showering for the day, My mind is not that fast anymore if it ever was?
It seems to me that there would be another test with this same bar of steel and electrodes etc, with the paper wet to should the drop in temp?

If it reported that the temperature reached 2000 C or 3632 F during the dry test and our ceiling for temperature is the last tempering of approx. 400 F Then wouldn't It be important to know what the actual temp reach with a known coolant is?

Anyone?

Laurence

www.rhinoknives.com
 
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