Stropping?

[Razor]

I was looking around on the spyderco forum and Cliff Stamp said when you strop a knife blade you just make the edge weak. It said the knife would hold its edge a lot longer by just finishing the edge on ultra fine stone. What do you all think? When I finish up on the sharpmaker I usually strop a few times.

 

[Twindog]

How does stropping make an edge weak? If you strop incorrectly, you can dull an edge, but not weaken it.

Rockstead recommends stropping to maintain the edges on its knives. Seems odd that they'd recommend a method designed to weaken the edges on their super refined and expensive knives.

You might also want to check out the 4-part Science of Sharp blog on stropping, as documented with electron microscope photos and with lots of discussion. Really a complicated subject.

https://scienceofsharp.wordpress.com/2016/05/29/the-pasted-strop-part-4/

 

[Gradyw]

This should be interesting.. never heard of cliff until I read the 36 grit push cut paper thread the other day.. that guy knows his shit and does all kinds of testing before he makes a decision on something. Atleast that's the way it seems in his videos. I'm interested to hear why he says that though

 

[HeavyHanded]

I was looking around on the spyderco forum and Cliff Stamp said when you strop a knife blade you just make the edge weak. It said the knife would hold its edge a lot longer by just finishing the edge on ultra fine stone. What do you all think? When I finish up on the sharpmaker I usually strop a few times.

Stropping doesn't weaken the edge but it can make it less acute.

Also, the edge develops a wear bevel in it during use. The apex gets less acute. As you repeatedly strop an edge to recondition it, unless the strop is very hard it can only sharpen the existing angle and it gets more broad over time - edge doesn't last as long.

If the strop is hard it isn't an issue, also people who strop more often, lighter touch etc.

Its conformable and that aspect has to be dealt with.

People that are better at some things than others will have different outcomes and different conclusions.

 

[Securis]

I think Cliff Stamp was referring to the burr, that when we strop, we sometimes transfer the burr from one side to the other repeatedly, causing metal fatigue on that burr, and when that burr is aligned straight or reduced to the point we cannot see it as a burr, can be a weak representation of the edge.

It'd be beneficial to see several video's on stropping. It's actually interesting to note how many people do it in a damaging method, i.e. - applying too much pressure.

One thing I've attained from learning how to sharpen knives - Patience, and taking the middle path.

 

[Obsessed with Edges]

Stropping poorly can definitely leave a weak edge, i.e., the burr created during honing on stones, if it doesn't get fully removed. But it shouldn't create a weak edge in itself, when done properly and to the rightful conclusion. It's actually pretty difficult to create a weakened edge or a burr on a strop, unless technique is really bad (heavy pressure and bad angle control, for example), and/or the materials used aren't appropriate to the job. 'Stropping' on something like sandpaper could do it (I've done it); but I don't consider that true stropping anyway, but just honing using a stropping technique. I've also created a burr on a piece of plywood, using a very, very heavy and aggressive stropping technique. But again, I was doing it 'wrong' by any standard of proper technique, mainly just to see if creating a burr could be done on bare wood at all (purely in the quest to learn something new ).


David

 

[Securis]

[video]https://youtu.be/XnhIKOX6Rco[/video]

Here's another take on it.

There are so many different philosophies and schools of thought. Gotta just try it all and see what is the best for you.

 

[Wowbagger]

Let me say this about that :

I HATE stropping

• vague and squishy
• Distorts the geometry unless it is done right (I have seen microscope images that show it doesn't distort the edge if done right . . . I don't feel like I can ever get it that right) did I mention I hate stropping ?

I hate to be a Cliff Stamp fan boy . . . I really do . . . but

• so many things I have "discovered" through pain staking trial and error (much error, much, much error) and then the clouds part and things fall in to place and the edge . . . or technique . . . or geometry . . . or steel (talking basic O' Swiss Army knife steel or Case SS . . . that cuts really well and stays sharp because of a drastic geometry change)
• The basic suckyness of some "super steels" that I won't go into
• the usefulness of pretty darned coarse stones over endless stropping and hoping

. . . well I watch Cliff Stamp vids like ten years after I "discovered" something to work and work well and here is Cliff Stamp talking about the same thing.

. . . counter intuitive stuff where ( "common sense" tells one it isn't going to help or work) physics and actually doing this counter intuive thing proves that yes inspite of "common sense" it is working well.

however
I don't think stropping makes an edge weak. I think maybe he is talking about bending the wire bur edge back and forth while stropping until it breaks off. His thing is apex sharpening where there is never much if any bur and one abrades the steel until the flattened (destressed) edge turns into a non reflecting apex.

but
stropping can . . . if not done right so the geometry isn't changed . . . it can make the performance for SOME applications WEAK due to changing the edge from an ideal geometry into a roundy obtuse useless thing.

Stroppig a few times, especially on soft stainless which is difficult to debur stainless, is going to debure the edge and help more than hurt.
On what I would call real steel like M390 or M4 there isn't a bur problem and so coming off a fine stone ONLY, with no stropping, is certainly the way to go.

Some of those funny steels starting with an S and ending with a V and ground all coarse can probably benefit from some diamond strop . . . I hate stropping . . . and still don't particularly like toothy edges so
for me I like a very coarse stone to get the geometry sorted out and back into spec. BUT then a few more progressively finer stones rather than coarse and then directly to a strop.

 

[Twindog]

Stropping is really best done after the burr is removed. It refines an already clean apex. The best way I've found to remove a burr is with edge-leading strokes, which is not stropping.

Freehand stropping can be a challenge for someone with little experience. However, guided systems like the Wicked Edge can make stropping a snap even for people with not much experience. The angle is already correctly set. All you have to do is use very light pressure -- and only a few strokes.

 

[HeavyHanded]

My definition of a strop is a bit broad as well. Anything where one can backhone and not raise a bur fits the bill. lapping films, some finer grades of sandpaper, resinoid waterstones, hard backed paper, scuffed hardwood. Even the basic leather strop can have a lot of variety in density and surface hardness. Hard treated ones are as dense as pine or even poplar.

 

[JD Spydo]

I've had mixed results stropping over the past 5 years or so. But I've got a set up now where I'm truly getting very consistent, optimal results. I have a Russian Boar Strop that I got from a Barber Supply Company a few years back and I lay it on a hard table where it has no give to it at all. And I've gotten some very desirable results that way. Also I do believe it does matter a lot what material your strop is made from.

I can only say good things about Cliff Stamp and I wish he would come back to the Spyderco forum. The guy knows his metals and different types of blade steel.

 

[noob93]

I usually strop on plain leather or denim. Usually after coming off of a 1000 grit Waterstone and have found it to help refine the edge. The edge usually goes from not shaving to shaving after the strop. My experience is limited but my results have been good. As far as weakening the edge iv not found that to be true. I strop my kitchen utility knife and it hold up fine.

 

[js1badsti]

I strop after using my edgepro but got my method on how to strop from the great apostlep--his youtube videos are the best I have seen--he is a natural at teaching in a way anyone can understand and learn.

 

[REK Knives]

I think Cliff's point is that an edge is metal, and metallurgy doesn't change. So what happens in use is that the edge gets either misaligned, fractured, or simply worn away and what a strop does (with compound) is to mostly move metal back into place when you have a roll/alignment issue, or even wear it can burnish the apex. Moving metal around like this, bending it back and forth, leads to weakened metal at the apex and thus a loss of edge retention. I have heard him use the paper clip analogy, when you bend it back and forth it will eventually break at the bend because of the weakened metal there.

A side note to consider in choppers and even in sharpening properly is that fracturing/damage can go below the apex into the actual edge itself, and when a strop re-aligns the edge it doesn't "de-stress" the edge by removing the fatigued metal for a fresh/strong edge.

Also the way most people use a strop doesn't necessarily help matters w/ a ton of metal loaded up in the strop vs. fresh abrasives on a fresh strop.

I don't know if Cliff has documented this in wear testing but I believe he has I just can't find it atm.

_________________

As far as damage below the apex... Todd notes here,

”It is important to remove this large burr with edge-leading strokes as the steel near the base off the burr will be damaged from the burr flipping side to side.”

Also Clay Allison demonstrates damage below the apex here,

 

[HeavyHanded]

I think Cliff's point is that an edge is metal, and metallurgy doesn't change. So what happens in use is that the edge gets either misaligned, fractured, or simply worn away and what a strop does (with compound) is to mostly move metal back into place when you have a roll/alignment issue, or even wear it can burnish the apex. Moving metal around like this, bending it back and forth, leads to weakened metal at the apex and thus a loss of edge retention. I have heard him use the paper clip analogy, when you bend it back and forth it will eventually break at the bend because of the weakened metal there.

A side note to consider in choppers and even in sharpening properly is that fracturing/damage can go below the apex into the actual edge itself, and when a strop re-aligns the edge it doesn't "de-stress" the edge by removing the fatigued metal for a fresh/strong edge.

Also the way most people use a strop doesn't necessarily help matters w/ a ton of metal loaded up in the strop vs. fresh abrasives on a fresh strop.

I don't know if Cliff has documented this in wear testing but I believe he has I just can't find it atm.

_________________

As far as damage below the apex... Todd notes here,

”It is important to remove this large burr with edge-leading strokes as the steel near the base off the burr will be damaged from the burr flipping side to side.”

Also Clay Allison demonstrates damage below the apex here,

Wouldn't the burr flip more readily/repeatedly on a hard stone than on a strop, even if its shrinking as it goes?

I'm not sure what testing has been done to rule out other factors contributing to edge degradation when stropping/backhoning is part of the prep, but have seen plenty of burrs not flip at all on a strop. I am unconvinced any burr will repeatedly flip on a strop that wouldn't be folding on the first light pass on a stone, nor will most strops be able to realign an edge. One would then be talking about plastic deformation or even flow using a comparatively soft material.

Once formed, the burr or folded edge will need to be removed with abrasives (either applied to a strop or some other surface) or smeared off via plastic flow on a very hard material (steel/glass). Standing it up, it will still be there = not removed. It doesn't matter if this was not accomplished on a stone or a strop or any other surface.

On hardwoods or even on paper over one of my Washboards I have observed some surface burnishing effect along the high points of a grind trough and at the apex, and it is possible to flip a burr or wire edge on a surface this hard, but nothing that would draw out the edge - they simply are unable to generate the level of unit pressure needed to do so without repeated hard application (many lbs of force over dozens of passes). If that were the case just using the knife will cause the edge to degrade faster than any dulling action if you compare lateral or steering stresses when cutting into wood grain or natural cordage for example to those encountered on a strop. Instead the edge is slowly worn away in all but the most abusive of applications. When an abrasive is combined with the higher unit pressure generated on harder strops, they are removing steel just as a polishing stone would and often at a similar or higher rate. The same mitigating factors of the hard stone are present in the harder strop.

It IS possible to fracture or fold the edge in use, but takes far more force than most would or could ever use on a strop.

As a note on subsurface damage to the steel structure, one is presumably doing far more harm in that regard by cutting directly into medium or coarse stones with the edge as an initial prep, than they would be just sharpening what's there.

Brent Beach:
http://www3.telus.net/BrentBeach/Sharpen/jig faq 02.html#thebest

A final thought, side by side testing of a variety of polishing grade waterstones will yield very different results when comparing backhoning to leading passes, tolerance to applied pressure etc. It is not possible to say "stropping does XYZ" without qualifying it with a description of the specific strop.

 

[Father & Son Traditional Sharpening]

I think Cliff Stamp was referring to the burr, that when we strop, we sometimes transfer the burr from one side to the other repeatedly, causing metal fatigue on that burr, and when that burr is aligned straight or reduced to the point we cannot see it as a burr, can be a weak representation of the edge.

It'd be beneficial to see several video's on stropping. It's actually interesting to note how many people do it in a damaging method, i.e. - applying too much pressure.

One thing I've attained from learning how to sharpen knives - Patience, and taking the middle path.

There is always a burr present, even if minimized to the point it cannot be felt or seen in any tangible way. This thin strip of steel is getting flexed back and forth during stropping, so it's only natural that burr would collapse at some point as bending steel repeatedly ultimately leads to breakage.

 

[HeavyHanded]

There is always a burr present, even if minimized to the point it cannot be felt or seen in any tangible way. This thin strip of steel is getting flexed back and forth during stropping, so it's only natural that burr would collapse at some point as bending steel repeatedly ultimately leads to breakage.

With any abrasive process, pressure is a necessary component. This would mean even on a hard stone with light pressure the base of the burr is being flexed back and forth just as it is presumably being done a strop.

Personally I haven't seen this in action or under high magnification, at least it is not a necessary outcome. Photomicrographs from other folk don't show this as a necessary outcome either. If the edge were that weak it wouldn't hold up to use even if it were cleanly sharpened. Any unilateral work would fold the edge over in short order. True, swapping sides will prolong the life of the edge, it will not reduce actual edge wear. The amount of unit pressure the edge sees in action is orders of magnitude higher than what it sees on any strop yet it does not collapse away except under very heavy use.

The only time I've reliably observed the edge flopping is from:

too high pressure being used on the stones, especially at the coarse level but can happen at any grit level on a stone if applied force is greater than the abrasive potential. If done at the coarse level it can turn into a true wire edge as it is worked with finer stones.

when backhoning a clean edge on hard stones just prior to the burr reforming. Most commonly on waterstones as this is a common finishing strategy, but applies to other stone types too. This is reliant on pressure as well, some stone compositions are very forgiving (resinoid waterstones) and some are not really suitable for backhoning in the first place (Arkansas, ceramic).

or overuse with a steel, grooved or smooth.

If a burr is so weak it is being folded on a strop and not cleanly removed, there is something else going on from an earlier stage that wasn't addressed, and/or the strop needs fresh abrasive.

 

[ToddS]

I was looking around on the spyderco forum and Cliff Stamp said when you strop a knife blade you just make the edge weak. It said the knife would hold its edge a lot longer by just finishing the edge on ultra fine stone. What do you all think? When I finish up on the sharpmaker I usually strop a few times.

Like most of what you will read about stropping, this is generally false. The exception will be when you form a "large" burr by repeated abrasion on one side. I would think it should be common sense to alternate sides near the end of the sharpening process to remove this type of burr. However, if you strop such large burrs on a non-abrasive (eg clean leather) or otherwise ineffective substrate, flipping the burr can torque the apex and introduce cracking and damage in the steel below the burr.

The smaller (and more typical) burrs that we usually deal are generally too flexible to torque the apex.