Stropping on loaded leather blunting a knife

[Cliff Stamp]

I have seen this reported a few times and did some experimentation with it last night. I was using a few of the softer stainless steel knives (AUS-6A class). I intentionally created a burr by applying too much pressure on the rods. This left the edge burnished like you would find on a cabinet scraper, one side shaved smoothly, the other didn't at all..

Using a leather strop loaded with CrO I gave the knife 5 passes per side. It was now fairly blunt and would shave on neither side. I assume the burr is cracking off on the first few initial passes. It takes then another 5 per side to get the blade to where it will catch a few hairs and the progression is slow but steady from then on.

This seems to be more of an issue with low machinability and brittle steels, which would make sense, but I would want to do a lot more checking to really say there is a definate difference personally. But those stainless steels in general do tend to get negative stropping comments, where hardly anyone complaints about 52100 or similar in that regard.

It would be beneficial to have a slightly more coarse abrasive to remove the burr if this method was to be used, some SiC paper works very well, 15/5 grit, then proceed to the 0.5 micron CrO, gives a quality edge really fast. Handamerican has an excellent setup for this type of sharpening.

-Cliff

 

[JDBLADE]

In general I would agree with your findings. I have always been of the view that one doesn't strop or steel a newly sharpened knife. A strop or a steel are used for maintenance of the edge and I have found if one takes a newly sharpened knife (even with a burr) to a strop or steel more damage is done to the edge. IMO a burr should be removed on the medium you use to sharpen the knife.

 

[Habeas Corpus]

Interesting observations. I don't have as much experience as most people around here, but I find stropping works best with straightforward carbon steels. 1095 for instance takes a very, very good edge.

I've also got a feeling some stainless steels don't take stropping very well. I gave up on stropping knives made of AUS6 well before I gave up using AUS6 at all ... I've also got one knife made of VG10 that doesn't like stropping at all, whereas my other knives in that steel take a really nice edge. That one knife just gets duller to the point it won't shave, and I'm using the same strops on all of my knives. Pretty odd that.

Would be quite interesting to hear other people's experiences on this. I'd also be quite interested to hear on what people feel about stropping knives with blades in S30V and S60V.

Hans

 

[Blue Sky]

I've had good results stropping on a leather strap charged with a small amount of Simichrome, layed on a hard flat surface. I've done this with 420HC, BG-42, AUS8 (I think), 154CM, 1095 and a Becker BK-11 (the steel grade # escapes me right now). I don't try to remove a burr with this method however, just polish an edge that's already as good as I can get with either ceramic rods or oil stone. It gets me as close as I can get to "hair popping" sharp.

Three things I've learned affect the results. First, do not raise the spine at the end of the stroke, keep it flat. Allowing the blade to come to a full stop at the end of each stroke helps me remember. Second, strop at a slightly shallower angle than you sharpened at. Third, don't press too hard.

I think the compressability of the leather is the reason for the second two items. You don't want the leather to curl around the trailing edge too much as it re-expands and round it off.

If you are breaking off a burr on the strop, I think you would need a very aggressive compound to clean up the resulting edge (probably ragged) in any reasonable amount of time.

 

[Cliff Stamp]

...what people feel about stropping knives with blades in S30V...

I took a Manix with a 10 degree primary edge bevel, created one with 15 then micro-beveled at 20. The resulting edge was shaving sharp on both sides, but one side was a hint sharper than the other. I then lightly stropped on CrO and the edge was significantly sharper and the hint of a burr removed.

I would propose that the pre-stropped edge is the critical factor. The higher it is in quality the better your chance or if being improved. A highly burred edge taken to leather or cardboard with a fine buffing compound will just act to degrade it. But if you can get the edge clean, then the fine stropping can be an improvement.

I think the main reason why the lower allow carbon steels tend to be favored for fine stropping is simply that they don't tend to form burrs in the first place. I would bet that if you did burr them they would respond in a similar manner on the strop. More experimention is needed.

-Cliff

 

[Fox Creek]

Very intersting Cliff. There are so many variables here that it might be hard to pin down, but I tend to think that once we agree that some steels simply do not respond well to stropping and eliminate them from consideration, that it is the condition of the edge before stropping that makes the difference. My experience agrees with that of Habeas Corpus. I routinely strop newly sharpened 1085 blades on an agressive hard leather strop to take off the coarse burr left by a Norton's Red India oil stone. I find that for a fairly thinly flat ground blade, this makes a very sharp edge that slices very well; I suspect that what I am getting is sort of a polished micro-seration. If the blade is not already fairly sharp, or newly sharpened with a burr, then the stropping doesnt do much and may even degrade the edge. It can be over-done. If you spend a lot of time getting a polished edge on a blade with several stones of successively finer grit, stropping would have an entirely different effect, and I can see where it could "un-do" things a bit.

 

[bzzhewt]

Are the lower end production steels (Aus-8, Aus-6, 420, etc.) on the list of steels that don't respond well to stropping?
Is Aus-8 particularly one of the complained- about steels?

 

[Cliff Stamp]

Are the lower end production steels (Aus-8, Aus-6, 420, etc.) on the list of steels that don't respond well to stropping?

Often they tend to get such comment as they are the steels which can burr heavily when honed on rods and thus when taken to a strop they degrade. They can be stropped but you have to take care not to get a strong burr on the hones, pre-stropping.

-Cliff

 

[Carl64]

I took a Manix with a 10 degree primary edge bevel, created one with 15 then micro-beveled at 20. The resulting edge was shaving sharp on both sides, but one side was a hint sharper than the other. I then lightly stropped on CrO and the edge was significantly sharper and the hint of a burr removed.

How much effort was involved in this? I would have thought s30v would respond poorly to stropping. Could it be the use of CrO vs other compounds?

 

[Habeas Corpus]

How much effort was involved in this? I would have thought s30v would respond poorly to stropping. Could it be the use of CrO vs other compounds?

I find diamond paste works very well for stropping S30V. After some experiments I settled for 10 mµ. Works pretty well.

Hans

 

[Cliff Stamp]

The ten degree primary bevel took a about five minutes on a belt sander. The 15 degree and 20 degree microbevels were a few passes per side, stropping was similar just a few passes, so just a few minutes.

I would not want to actually try to restore a blunted knife with CrO, it is way too slow as a cutting compound. However if the edge is well formed with stones it can be made sharper pretty much independent of the alloy with a light stropping.

What I am curious about is does this actually improve the edge or does it weaken it and how does it effect slicing aggression. I have some identical test blades that I plan to test this out on shortly. Of course you could also just use finer stones to finish the edge such as the UF Spyderco rods.

-Cliff

 

[Dave Rishar]

Between the polishing compound being used, the condition of the strop, the stropping technique being used, and individual differences in the knives themselves, I'd guess that there are too many variables here to give a definitive answer.

When I'm doing an initial sharpening or reprofiling on the belt sander, I normally wind up with a good-sized burr at the end, regardless of what kind of steel I'm working with. One thing that I like to do is to make two or three hard slices on a block of wood prior to stropping. This almost always removes the burr.

I get the impression that stropping reduces the slicing ability a bit - no numbers to back it, just my observation. It doesn't seem to reduce it very much though.

I intentionally convex the edge a bit on the belts and work to maintain this with the strop, so in my case I wouldn't think that the edge is being weakened. YMMV.

 

[Cliff Stamp]

Yes, there is a lot of room for variation here, and a lot of avenues to explore. Stropping on SiC/diamond sandpaper is obviously a lot different than CrO on leather. I started this mainly from some comments I heard about some steels degrading which doesn't make sense from an abrasive point of view.

-Cliff

 

[Cliff Stamp]

I tried this with some carbon steel blades, a Mora, 52100 custom, and SR101 Howling Rat, I intended to create an edge which had a significant burr and then take it to a CrO loaded strop to watch what happened. All three blades formed perfectly crisp edges on the Sharpmaker flats, not a hint of a burr. This is probably why carbon steel blades + stropping tend to be so well suited, they usually have a much better match of wear resistance and hardness than the stainless steel blades. It would be informative to have Wilson reharden some of the stainless blades to near full hard and see if that improved them.

-Cliff

 

[Carl64]

This is probably why carbon steel blades + stropping tend to be so well suited, they usually have a much better match of wear resistance and hardness than the stainless steel blades.

That's what I have thought for a while, but I don't know enough to form any kind of theory on it. There are numbers for hardness, but is there any standard test or measuring system for wear resistance?

I would like to be able to say something like "at rc60, a blade should have about X rating for wear resistance," or maybe "Hardness:wear should be at least (or maybe no more than) 1:1" or something like that. It seems obvious to me, if not to many others, that wear resistance does no good if the blade simply folds over, and hardness does no good if the molecules are pulled apart too easily.

I know there are many terms used to describe a blade, but it seems like hardness and wear resistance are the biggest ones under non-damaging use. There ought to be a quantifiable way of describing both of these.

Spydercos with H1 steel have nothing but happy users, but long-term tests are still scarce. After some initial weirdness on the first few uses, it now takes a fine edge with little burring almost like I would expect from a simple Carbon steel. Depending on who you ask, it has either medium or fairly high hardness, but definitely very low wear resistance as I found when polishing it. I asked about the CATRA results for this steel compared to others on the SPyderco forum here, but received no answer.

 

[Cliff Stamp]

There are numbers for hardness, but is there any standard test or measuring system for wear resistance?

There are standard materials tests for both machinability and wear resistance, Crucible references them occasionally in their steel spec sheets.

...wear resistance does no good if the blade simply folds over

The only real advantage this has is if you are willing to put up with a really low sharpness, a rolled edge which resists wear will stay in that condition for a long time. By low standards I mean a sharpness of a few percent of optimal, a lot of people will use blades in really degraded conditions.

-Cliff

 

[UnknownVT]

I'm not sure if this is relevant - but I used to have problems stropping after sharpening using crock-stick/V-hone - finding the blade less sharp after stropping, to the point of feeling they were blunt (so I may have been one of the earlier complainers... ).

Now I don't have that much problems - from a simple change of stropping habit.

I even use a less "controllable" leather strap type strop.

It was so stupidly simple, that I didn't think it was possible.

The simple change in stropping habit was to flip or roll the blade over its back or spine - instead of what felt more natural for me of flipping it over the edge.

I knew well about not raking the blade edge on the end of a stropping stroke, and was careful to always lift the blade clean off the strop. But as the evidence shows me I probably was still raking the blade edge even when I was being careful.

Whereas fliiping or rolling the blade the other way over its back or spine - seems to have cured the problem for me.

There are times when I still feel a freshly sharpened blade from a fine ceramic crock-stick V-hone may feel more aggressive - but I think that's more to do with the "micro-serrations" from a coarser finished edge.

I also now do a lot of stropping on cardboard to touch up and maintain my blades with very good results. My home-convex edged Victorinox SAK and the stainless Opinel #8 respond really well to that - and I consider these pretty scary sharp, and both these stainless steels are consider by most "soft" - but I do have to remember to flip/turn the blade over its back or spine....

[sorry for the lateness of this response - I have been having NO end of problems for 3 days attempting to post a response - when clicking on the Preview or Submit post button locks-up my IE6 browser - and the only option is to use CTRL-ALT-Delete and end the Not Responding BladeForum (IE6) task -
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[Cliff Stamp]

Yeah, the edge turning is a frequent problem. Here though it is more an issue of pre-stropping condition of the edge. I think any steel should respond to a light stropping as long as the edge is decently crisp pre-stropping.

I have run a few tests on the stropped edge, and they are much more durable, with significantly greater edge retention (many to one). This isn't an arguement for stropping however, as much as it is one of burred vs crisp edges.

-Cliff

 

[UnknownVT]

Cliff Stamp wrote

it is one of burred vs crisp edges.

I don't think I normally try to strop a blade with a noticable burr.

Although in mitigation softer stainless steels will have a tendency to roll-over their edges when using more pressure with ceramic crock-sticks - so I may have stropped rolled-over edges earlier without being aware of it.

However I do strop quite hard on cardboard these days as it seems very controllable to me - but it is probably normally on un-burred edges.

Sorry for the non-standard Quote - but the default form of QUOTE=username seems to be root of my IE lock-up problems.

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[Cliff Stamp]

Although in mitigation softer stainless steels will have a tendency to roll-over their edges when using more pressure with ceramic crock-sticks

Yes, this was one of the things I wanted to explore, it seems to be at the root of the problem.

-Cliff