Welcome, Guest
Username: Password: Remember me

TOPIC: Interesting video... do you destress your edge?

Interesting video... do you destress your edge? 11 months 1 week ago #13510

  • limpy88
  • limpy88's Avatar
  • OFFLINE
  • Junior Boarder
  • Posts: 28
  • Thank you received: 10
  • Karma: 3
razoredgeknives wrote:
While I don't have any proof at this point =) Think about it... dunking your blade in a bucket of water while using it (post heat treat) with a belt sander is a pretty common practice, otherwise you WILL over heat it if you are doing any serious amount of metal removal or reprofiling (which you would be to put the final edge on it post heat treat). It may or may not be the case, but is an interesting theory none the less.

I took a relook at the you tube video of Bark river knives shop tour. The showed the employees dipping the knives in water while putting the edge on then. :blush:

But while searching, the act of destreesing a knife is usually a heat treat process called "normalizing". Where a forged blade is softened to allow the initial grinding to take place. What he is doing isnt de stressing the edge, as the original edge metal is long gone. How can u de stresss something that isnt there

It would be interesting to see the results of a Rockwell hardness test of the new edge. Maybe the initial heat treat wasnt done properly on the first batch of knives. Or they surfaced hardened the knife edge in properly but the initial heat treatment was correct and the countless sharpenings made it past the surface harding.
The administrator has disabled public write access.

Interesting video... do you destress your edge? 11 months 1 week ago #13511

  • razoredgeknives
  • razoredgeknives's Avatar
  • OFFLINE
  • Platinum Boarder
  • Posts: 702
  • Thank you received: 304
  • Karma: 38
Yeah ;) He isn't referring to normalizing, which is a step just prior to heat treating. What Cliff is referring to is this. When you use your knife the edge gets dented bent, and chipped with the various peaks and valleys (i.e. micro-serrations) basically suffering the damage. When you strop, "steel," or even lightly sharpen your knife, it weakens your edge due to the metal at the very edge being bent back and forth. Destressing would be removing the weak metal by cutting 90 degrees into a sharpening stone to remove the damage before actually sharpening to put a clean, fresh edge on it that is stronger. This is how the theory goes anyway :side: Makes sense to me as it is commonly accepted that metal weakens the more it is bent.
The administrator has disabled public write access.

Interesting video... do you destress your edge? 11 months 1 week ago #13513

  • EamonMcGowan
  • EamonMcGowan's Avatar
  • NOW ONLINE
  • Platinum Boarder
  • Posts: 518
  • Thank you received: 193
  • Karma: 28
Think about it... dunking your blade in a bucket of water while using it (post heat treat) with a belt sander is a pretty common practice, otherwise you WILL over heat it if you are doing any serious amount of metal removal or reprofiling (which you would be to put the final edge on it post heat treat). [/quote]

Please excuse my ignorance? When grinding a knife how hot is to hot? I've heard if you can still hold the blade it never got hot enough? I've had it pretty hot as I pull away from the pass but it drops rapidly in the next two seconds. But never hot enough that you just could not touch it?
What do you guys think? Thank you,
Eamon
The definition of insanity is to do the same thing over and over again and expect a different result?
An old Irish toast, May the wind always be at your back, may you always have work and may you be in heaven a half hour before the devil knows your dead. Cheers!
The administrator has disabled public write access.

Interesting video... do you destress your edge? 11 months 1 week ago #13522

  • cds43016
  • cds43016's Avatar
  • OFFLINE
  • Fresh Boarder
  • Posts: 10
  • Thank you received: 5
  • Karma: 2
I keep pretty detailed sharping records even though most of the knives I sharpen are pretty low quality.
One thing I noticed is that sometimes for a particular knife the first few sharping’s turn out marginal at best. Each time I sharpen it, the better the edge becomes.

Early on I thought it was the WEPS learning curve. I was just getting better at using the tool. But it still happens after many knives and many incredible first edges. I then thought maybe it was the steel. But if it was the steel should not the edge remain marginal on every sharping? Something else must be the happening.

Like I said most knives that I have fall in the budget price category. Most people I know don’t use quality knives. If it’s good enough for Ron Propiel, it’s good enough for them. Other than my own knives, I rarely get high quality knives to sharpen. Low quality knives can still get razor sharp but just don’t stay that way for long.

I had a knife that I got from my junk box, a Farberware Chef knife. It was a dull as a board. I wanted to use it to practice the speed techniques as discussed in another tread. I started with the 80 grit stones and followed the progression to 600 grit. Eight minutes later I still had a pretty dull knife. Better but it was in no way acceptable.

OK I’m not doing something right. I did it again and got the same result; a little better but not good. It would not cut printer paper cleanly. Now one more time – same result (is this the definition of insanity – doing the same thing over and over and expecting a different result?). Now I’m thinking the knife is junk but still I should have gotten better results. I then decided to go for it and do a proper WEPS sharping. After about half an hour down to 1000 and strops, it was getting better but still struggled through printer paper. It was a lot better but nothing to write home about. I did get a burr on the course stones which accounted for most of the sharping time. The burr was weak and hard to get, but it was there. It must be the type of steel I thought and was ready to give up. The knife was just trash. Then I decided, after seeing this tread, to take a few minutes on the belt sander to see what I could do. I didn’t want to spend too much more time on this knife, but I wanted to see what would happen if I ground it down further. I had nothing to lose.

I used 80, 40 and 9 micron belts and in less than 10 minutes the knife would glide through phone book paper! I have other records of knives I started on the belt sander that were fair and after a sharping on the WEPS razor sharp. The reverse of what happened here. It’s not the tool; something else is going on. It may be the way the knife is made; maybe the way it was heat treated or the way it was sharpened at the factory that affected the steel. I think I see more of this and it may be more pronounced given the kind of knives I get to work with.

I’m not a metallurgist just a hobbyist so I don’t know. What I see lends weight to the theory that the steel at the edge is inferior to the steel further in whatever the reason. It’s a matter of how far you have to go to get to the ‘good stuff’. I must not have gone deep enough with the WEPS but must have been close. Maybe another sharping would have gotten me there. I also know for some really cheapo knives there isn’t any good stuff.

For some knives distressing the blade may have value. I have in my records where I did several passes with a file to clean up a really rough edge and the results have been very good. I can’t say that distressing caused the good final result but it sure didn’t hurt. Distressing may help in some cases get to that good steel quicker. I would not distress a blade as a matter of course, however, especially on a good knife. But it may be something to try if you are not getting the results you think you should be getting.
The administrator has disabled public write access.
The following user(s) said Thank You: cbwx34

Interesting video... do you destress your edge? 11 months 1 week ago #13524

  • cbwx34
  • cbwx34's Avatar
  • OFFLINE
  • Moderator
  • Posts: 1260
  • Thank you received: 413
  • Karma: 92
razoredgeknives wrote:
Yeah ;) He isn't referring to normalizing, which is a step just prior to heat treating. What Cliff is referring to is this. When you use your knife the edge gets dented bent, and chipped with the various peaks and valleys (i.e. micro-serrations) basically suffering the damage. When you strop, "steel," or even lightly sharpen your knife, it weakens your edge due to the metal at the very edge being bent back and forth. Destressing would be removing the weak metal by cutting 90 degrees into a sharpening stone to remove the damage before actually sharpening to put a clean, fresh edge on it that is stronger. This is how the theory goes anyway :side: Makes sense to me as it is commonly accepted that metal weakens the more it is bent.

Maybe instead of "destressing" simply "cleaning up" the edge, might be a better description.

EamonMcGowan wrote:
razoredgeknives wrote:
Think about it... dunking your blade in a bucket of water while using it (post heat treat) with a belt sander is a pretty common practice, otherwise you WILL over heat it if you are doing any serious amount of metal removal or reprofiling (which you would be to put the final edge on it post heat treat).

Please excuse my ignorance? When grinding a knife how hot is to hot? I've heard if you can still hold the blade it never got hot enough? I've had it pretty hot as I pull away from the pass but it drops rapidly in the next two seconds. But never hot enough that you just could not touch it?
What do you guys think? Thank you,
Eamon

If I do something major on a belt sander, my approach is to use water to keep the blade cool, not to cool it off once it gets hot. If you make several passes, you can feel heat build up in the blade, and eventually it won't "pull heat" from the area being worked. So, I try to keep it cool and avoid the blade getting hot (or even very warm) in the first place.
Last Edit: 11 months 1 week ago by cbwx34. Reason: Fixed quotes
The administrator has disabled public write access.
The following user(s) said Thank You: EamonMcGowan

Interesting video... do you destress your edge? 11 months 1 week ago #13542

  • razoredgeknives
  • razoredgeknives's Avatar
  • OFFLINE
  • Platinum Boarder
  • Posts: 702
  • Thank you received: 304
  • Karma: 38
Thanks for the input guys!

I had a REALLY interesting conversation with a super smart metallurgist (who primarily works in the scissor industry) about metal. I asked him if powered sharpening equipment (i.e. belt sanders) will indeed damage the last few microns of the edge even if its unseen. He said on a very microscopic level but it would not make any noticeable difference to the user. He said that it isn't until the edge starts to actually change color that you begin to possibly damage things - light tan means it is still recoverable by making a few more passes but if its blue your done and the temper is ruined.

He gave an analogy of a metal mill... he said that sharpening with a powered stone/belt is the same thing but on a much smaller scale - i.e. a mill carves out chunks of metal whereas a belt sander carves out small pieces of metal. It all has to do with heat transfer... He stated that even under a water cooled system the heat is still being generated, it is just washed away very quickly and transferred into the coolant. Well, in the above scenario when a piece of metal is carved away by the abrasive on a belt, approximately 75% of the heat is transferred away from the blade itself - this is why you have a spark.

Also stated that its not required for you to have time AND heat to damage the temper, but just heat alone can do this. Kevin Cashen (I believe) a few years ago did some scientific research where he measured the head on the sub micron levels of the edge with micro-thermo couples. He found that just moving a piece of metal across dry sandpaper by hand generated around 2000F for a nano-second. So my converstion with this metallurgist was quite interesting =)
The administrator has disabled public write access.
The following user(s) said Thank You: wickededge, cbwx34

Interesting video... do you destress your edge? 11 months 1 week ago #13562

  • EamonMcGowan
  • EamonMcGowan's Avatar
  • NOW ONLINE
  • Platinum Boarder
  • Posts: 518
  • Thank you received: 193
  • Karma: 28
razoredgeknives wrote:
Thanks for the input guys!

I had a REALLY interesting conversation with a super smart metallurgist (who primarily works in the scissor industry) about metal. I asked him if powered sharpening equipment (i.e. belt sanders) will indeed damage the last few microns of the edge even if its unseen. He said on a very microscopic level but it would not make any noticeable difference to the user. He said that it isn't until the edge starts to actually change color that you begin to possibly damage things - light tan means it is still recoverable by making a few more passes but if its blue your done and the temper is ruined.

He gave an analogy of a metal mill... he said that sharpening with a powered stone/belt is the same thing but on a much smaller scale - i.e. a mill carves out chunks of metal whereas a belt sander carves out small pieces of metal. It all has to do with heat transfer... He stated that even under a water cooled system the heat is still being generated, it is just washed away very quickly and transferred into the coolant. Well, in the above scenario when a piece of metal is carved away by the abrasive on a belt, approximately 75% of the heat is transferred away from the blade itself - this is why you have a spark.

Also stated that its not required for you to have time AND heat to damage the temper, but just heat alone can do this. Kevin Cashen (I believe) a few years ago did some scientific research where he measured the head on the sub micron levels of the edge with micro-thermo couples. He found that just moving a piece of metal across dry sandpaper by hand generated around 2000F for a nano-second. So my converstion with this metallurgist was quite interesting =)

So if the blade it gets hot to touch but no color change? your good to go??
The definition of insanity is to do the same thing over and over again and expect a different result?
An old Irish toast, May the wind always be at your back, may you always have work and may you be in heaven a half hour before the devil knows your dead. Cheers!
The administrator has disabled public write access.

Interesting video... do you destress your edge? 11 months 1 week ago #13565

  • razoredgeknives
  • razoredgeknives's Avatar
  • OFFLINE
  • Platinum Boarder
  • Posts: 702
  • Thank you received: 304
  • Karma: 38
EamonMcGowan wrote:
So if the blade it gets hot to touch but no color change? your good to go??

Basically! If you can touch your edge immediately after taking it off of the belt and don't burn yourself you shoudl be good to go.
The administrator has disabled public write access.

Interesting video... do you destress your edge? 11 months 1 week ago #13567

  • PhilipPasteur
  • PhilipPasteur's Avatar
  • OFFLINE
  • Platinum Boarder
  • Phil
  • Posts: 944
  • Thank you received: 233
  • Karma: 66
razoredgeknives wrote:
Interesting observation and theory about how the edge can get "burnt" at the factory and have an initial low sharpness/edge holding ability.

He does not offer a theory, but an unsubstantiated guess, that he presents as fact. It sounds somewhat plausible, but without objective evidence, this is just another guy on the Internet saying... something.

Your question about "de-stressing" probably a bad term for what he is doing as Curtis alludes to...
I have never found the need to do it, so I have not.

I have sharpened a bunch of knives on my belt grinder. The knives of crappy steel with low edge retention, remain that way. Likewise, the better steels still show the properties that warrant spending the extra money for a knife with good steel. They take a good edge, and stay that way for a long time.

Eamon,
I don't quench at all when doing a typical sharpening job... minor re-profiling and sharpening.

When I do repairs, I will use cold water if I feel heat in the blade. Some may say that this is too late, but I have not seen any problems with those blades. All anecdotal information... but I don't claim to have any theories on this..
:)
Phil

MAX 2001-2013
Hoping there is that bridge!
I miss you Buddy!
The administrator has disabled public write access.
The following user(s) said Thank You: cbwx34

Interesting video... do you destress your edge? 5 months 3 weeks ago #15813

  • CliffStamp
  • CliffStamp's Avatar
  • OFFLINE
  • Junior Boarder
  • Posts: 35
  • Thank you received: 49
  • Karma: 12
In regards to edges and over heating, as Roman Landes has discussed at length, the apex of a knife is literally < one micron wide so damage to the edge on an order of a micron will affect the properties of the steel in regards to edge holding / durability significantly. Roman has presented data on this as Ashokan (published material sources) on multiple occasions and he is very active on HypeFree and has provided more detail on this topic there.

The reason why intermittent water cooling is not a good idea is because :

a) those steels are not meant to be water quenched

b) the very edge will rapidly contract and if you cycle this over and over it will crack

These are not conjecture or ideas, they are known in metallurgy, and arguing against it is like saying that free chromium in steel doesn't add to corrosion resistance.

As a few points of correction :

-you can not judge the temperature of the apex from feeling the blade because the very apex cools rapidly in air and it has a very low heat capacity because the volume is small

Years ago I (and others) did a simple experiment where we burned blades to black and still kept our hands on the blade, you can not use this as a means of controlling temperature.

In regards to scaling, the colors you see are oxidization, similar to rust and just like rust they are resisted by stainless steels (and other alloy steels) and thus those steels have to get much hotter before they scale.

But again, you are concerned about the last micron of the edge, you can't see that anyway, the visible ability of most people is in the 20-40 micron range, a sharpened edge is on the order of 0.1 micron, if the damage is 10 microns you won't see it but the edge holding/durability is completely obliterated if you are interested in a sharp edge.

In regards to why I called it destressing is because that is what it does, it removes the metal on the edge which was fatigued / stressed in use and ensures that when the knife is sharpened then the apex forms on quality metal. The label is also critical as it promotes the understanding of how a knife blunts and what you need to do to sharpen it (removed the stressed metal).

I started doing this after a series of experiments I did years ago where I compared sharpness by normal "touchup" methods vs what I called full sharpening (which included cutting the edge off). After concluding that the latter was significantly better I did the research to figure out why it happened and it is known in metallurgy that the damage will be beyond the immediate blunting.

I did those experiments when I noticed that edge holding after steeling and stropping was significantly less than the edge holding from the initial sharpening and as well if I extended it for a long time the edge would at some point fail catastrophically by fracture.

As an aside, this destressing also :

-prevents formation of recurves and any uneven edge grinding as the light line will tell you of problems long before you would other wise notice them

(if the light does not reflect in a consistent thickness there are issues which should be resolved)

-is a great visual aid because once it is removed you know you are 20-40 microns away from a sharpened edge and you can switch to your finishing stones and not put coarse shaping scratches to the very apex

In regards to that Benchmade, the loss of steel wasn't because of the destressing, it was because it was in use for seven years and that use/sharpening obviously caused metal loss.

There is a long history to that knife, it was a replacement for a knife which was defective. That one was also found to be defective by the original owner who was told by Benchamde it was his problem as he was newb (that is what he noted they tried to make him feel like). The owner sent it to me and I concluded it was indeed defective, he wasn't.

The problem is :

-lack of initial sharpness
-poor edge holding (for that steel)

They are both related to the same problem which is the edge fractures. If you check it under magnificantion you can see that the edge fractures at a size well above the scratch pattern.

It is possible to sharpen it decently, but it requires :

-micro-loading, 5-10 grams of force on the abrasive (which has to be very clean, flat, etc.)
-heavy micro-beveling/back sharpening (burr minimization)
-cross scratching the grits (burr minimization)

Of course if it is that fragile in sharpening, it is that fragile in use.

Ironically, my brother doesn't care about that much at all because he uses knives in a semi-dull state (the edge is ~10 microns thick) and at that level of thickness it is stable enough and the high carbide volume keeps it there for a while.

I got it back off him after that long as the edge had thickened and he wanted the primary grind planed down. I did that and confirmed the low edge retention on cardboard was still there : www.cliffstamp.com/knives/reviews/cardboard.html . Note how poor it does compared to the other S30V blades, it not only isn't Class III, it isn't even Class II.
The administrator has disabled public write access.
The following user(s) said Thank You: wickededge, leomitch, razoredgeknives, mark76
Time to create page: 0.260 seconds