Stropping on loaded leather blunting a knife

[Cliff Stamp]

I took a few of the softer stainless steel blades and redid the sharpening and got a decently crisp edge and then they responded excellently to the CrO loaded leather strop. The sharpness increased significantly as did the edge retention.

-Cliff

 

[UnknownVT]

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Cliff Stamp wrote - QUOTE: I took a few of the softer stainless steel blades and redid the sharpening and got a decently crisp edge and then they responded excellently to the CrO loaded leather strop. The sharpness increased significantly as did the edge retention.UNQUOTE
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Thanks for the follow up Cliff.

For most of us (well, OK read "me") we don't do things that are well controlled and reproducible - and often can come to conclusions that may not actually be or corrolate to the cause.

So I appreciate your report of what I seem to experience in stropping.

My own stropping experience can hardly be called conclusive or even anywhere near expert - since until fairly recently I was not even aware that I was actually raking the edge by doing an edge flip.

However I did know not to strop a blade with any noticable burr.

It's kind of like trying to get a good paint/varnish finish on things - if any stage is incomplete - then the end result would be lacking.

IMHO this applies in sharpening too. each stage should be completed - normally for me is raising the burr with a coarser stone - honing off that burr with that stone - then move on to the next (fine) grade - where a burr (or at least a prominent burr) is not usually raised - get the honing finished with the fine stone - getting the best edge possible out of that stage - before any stropping.

Your tests and evidence shows that skipping or short-cutting any stage could end up with undesirable results - especially for softer steels - which actually seems to be the norm in real professional usage - like in meat cutting/packing etc.....

--
Vincent

http://UnknownVT2005.cjb.net
http://UnknownVT.cjb.net
http://UnknownVincent.cjb.net

 

[sodak]

This has been an interesting thread, thanks Cliff.

I have seen some recommendations to strop the burr off, but I always thought that would be counterproductive as now you have embedded metal in your strop. I have noticed AUS-8A get insanely sharp with stropping, but not with Cr0 or any other compound, just the sticky stuff that knifeworks sells for straight razors. S30V has also responded well for me for this kind of stropping, but loses the "scary" edge quickly.

I have another strop shipping and when it arrives, my old one will get loaded with the green compound from Hand American and perhaps then I can experiment a little more.

Back to burr removal, several people have recommended adjusting the edge angle slightly and removing it that way. I've seen others recommend lightly running the edge over wood (perpendicular) a couple of times. What do you think?

 

[Cliff Stamp]

each stage should be completed

This is one of the most common problems. You don't do enough work with the x-coarse hone, or leave the edge heavily burred. Every stage of the sharpening should leave the edge very sharp, raising the grit is fine, but do it on a less than optimal edge and you are just giving yourself a hassle.

S30V has also responded well for me for this kind of stropping, but loses the "scary" edge quickly.

There have been a number of soft S30V blades reported, when this is hard, ~60/62 HRC it should remain crisp well, however some are running it really soft.

I've seen others recommend lightly running the edge over wood (perpendicular) a couple of times.

That is akin to removing a pain in your foot by amputation. It solves the immediate problem by creating a worse one. The most efficient burr removal method is to not create it in the first place, when one does come up, raise the angle, create a micro-bevel, and cut it off and continue as normal.

-Cliff

 

[UnknownVT]

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Cliff Stamp wrote - QUOTE: That is akin to removing a pain in your foot by amputation. It solves the immediate problem by creating a worse one. The most efficient burr removal method is to not create it in the first place, when one does come up, raise the angle, create a micro-bevel, and cut it off and continue as normal. UNQUOTE
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Had to smile at that analogy

But that's not strictly true - many sharpening books and instructions tell us to raise a burr - to make sure we have actually honed right to the final edge.

But usually honing the other side right to the edge will hone off that burr.

Leaving a promient burr and stropping seems to lead to problems.

Have you thought about why?

Do you think it's because breaking off the burr leaves a non-crisp edge?

Or since it appears to affect softer steels that the burr is actually rolled over and leaving a folded over edge?

Have you looked at a typically affected edge to see what might be causing this blunting, while harder steel do not seem to be as badly affected?

Thanks,

--
Vincent

http://UnknownVT2005.cjb.net
http://UnknownVT.cjb.net
http://UnknownVincent.cjb.net

 

[Carl64]

That is akin to removing a pain in your foot by amputation. It solves the immediate problem by creating a worse one. The most efficient burr removal method is to not create it in the first place, when one does come up, raise the angle, create a micro-bevel, and cut it off and continue as normal.
-Cliff

Previous experiences with the problem suggest otherwise for me. I would speculate that the existence of a severe enough burr bending back and forth might have continued to weaken the steel just below it some.

It's not really worse because, unless you break away more steel than necessary when getting rid of the burr, you would have had to do as much careful sharpening anyway to grind away the weakened burr from the side as opposed to breaking it off. This assumes you goal is to create an edge from "good" steel by completely removing the weakened steel, not just wearing down enough of the burr to get the edge sharp.

I also found it hard to know exactly how far away I was from being done when the burr was still not gone. Kind of annoying.

 

[mlovett]

Gotta get in on this one. People keep using non cutlery grade steelsto manufacture their wares, and the buying public keeps wondering why they get non cutlery grade results in the products. they buy.. The problem is "NOT" stainless type steels. Its steels that are not worth taking home. Yes the simple minded,(oops, simple carbon steels) work, because they have enough carbon in the mix to go thru the transformation from course to fine grain structure. Low carbon steel will "NOT" work. You would never dream of buying a knife if you were told it was cold rolled or low carbon.. Its
construction grade, metal. Suited to making brackets, or any number, of other mundain items. Not cutting insturments. The same applys to Stainless steels. There are Low carbon stainless, steels, and High Stain resisting steels. Do not confuse the too. they are not even closely related. aus6 and 440, 440-a, 440-b aus-8, 420, are low to medium carbon. Not able to go thru the transformation. Heck. 420, aus-6, and 440-a, arn't much better than what I use for guard material. Proper Stain resisting steel, 440-c, (The "C" stands for cutlery Grade), ATS-34, SV60, CPM440, AUS-10, /Are High carbon steels with enough other elements added to aid in Stain resistance, strength, shock resistance, and edge retention. No you can't simply stick them in a fire and beat the crap out of them, they require first class Heattreating. This will most definatly produce a superior blade.. If the edge is rolling, or buring. during sharpening, Either the steel is to low in carbon, Too soft. or the sharpening method is lacking. I've found that if a very fine diamond hone is used, there will be no burr, even on low quality steel. Yet leaving micro teeth, that will bite, and can be stroped. Stropping a Low quality, steel, with out the micro teeth will result in nothing more than a polished, bearing like edge. Might even shave a little, but won't cut well or last at all. We use this trick when going to shows, even on highcarbon. Polish the edge very fine. Shaves like a stright razor, won't cut hot butter. Customers love to shave their arms. But they no longer bleed all over my table. If they buy the knife< I litely touch it up on an ultra fine Diamond Hone. Cuts Like A Lazer! If for any reason some of you think I'm a newbie, try, http://home.earthlink.net/~michaellovett/ Thanks Guys Oh yes, I almost forgot. Surgical Stainless. It only means that it doesn't rust or corrode at 212 degrees F.. Nothing to do with cutting at all. It's given S/S, a bad rap. for years. Should be called super Junk.

 

[Cliff Stamp]

...many sharpening books and instructions tell us to raise a burr

I think this is a solid introduction, but you should eventually move beyond this and not focus on just getting a burr, but how to get a final crisp edge and this means removing the burr, and with some steels this means you have to be very careful not to create a large burr in the first place.

Do you think it's because breaking off the burr leaves a non-crisp edge?

Yes, if it was just folded over you would be able to detect an edge bias. There are a couple of things which should be noted. The first is that after you have stropped the knife and the edge breaks and then gradually reforms, when it is maintained on the strop from that point on the edge doesn't break and reform again, it now responds well.

I finally got a carbon steel blade to do the same thing. It was an old blade with a full patina, probably not sharpened in years. I ground the edge on a belt sander, recut it with a x-coarse hone and then touched it up on the Sharpmaker, however the edge was weakened from extensive use and so it just burred rapidly on the Sharpmaker and as predicted went blunt immediately on the strop.

I then recut the edge with a file, removing a decent amount of steel and now the edge went crisp on the Sharpmaker and responded well to the CrO on leather.

I also found it hard to know exactly how far away I was from being done when the burr was still not gone. Kind of annoying.

There are some times when the increase angle grinding method can fail and fail horribly, at times I have found it necessary to grind an edge fresh. I usually grind the whole relief grind in these cases to reset the edge but if I wanted to do it quickly I would grind the edge at a 90 into the stone to cut the weaken metal away.

The problem I have with the "cut into a piece of wood" method is that this is often implied as a solution to the burr problem and that the edge it leaves behind is actually an optimal one, all you have to do is crack off a burr and the problem is solved. Of course this isn't the case, what you have to do is get the edge formed from quality steel.

You would never dream of buying a knife if you were told it was cold rolled or low carbon.. Its
construction grade, metal. Suited to making brackets, or any number, of other mundain items. Not cutting insturments.

I have made knives from such metals, a piece of tension bar from a fence, it can easily take a coarse edge for slicing ropes or a polished edge for shaving. Ref :

http://www.physics.mun.ca/~sstamp/knives/tension_bar_proto.html

-Cliff

 

[Cliff Stamp]

So I am doing some cardboard cutting and after the blades have blunted I restore by steeling (35 degrees, smooth steel, edges were initially set at ~5 degrees, highly polished on a natural chinese stone).

So I think to myself, "Hey self, why not strop the edges on CrO loaded leather and check your theory about removing a burr on loaded leather and edges cracking off?"

I take a Meadowlark, the edge is biased as are all burnished edges. As it hits the strop I can feel the edge aggressively catch and as expected it is blunted initially and by the 10'th pass is improving and in another few passes it is shaving.

So I think to myself "Self you are brilliant, another excellent innovation, you really understand this knife business you should write a book. But even though you are obviously right, check it with the other blades just to make sure."

I take a S30V Senenza also blunted (same media), steel it, same thing, sharp on one side, strop it, and it gets sharper right away, and by the fifth pass is shaving very well on both sides.

Hmm, ok, it responded faster than the Meadowlark? Maybe it was a fluke, something really odd happened, maybe mars was just inline with venus or Prince changed his name again, before you get all excited, check another blade.

So I take a 1095 custom, steel it, same thing, edge biased, strop it and it gets sharp right away again, just like the S30V blade.

Now what the hell happened here. How come the 1095 and S30V blade didn't get dull initially as all the other blades did before, there is no way the CrO abraded them and formed a crisp edge immediately.

The only think I can figure is that the edge burr just straightened out on the S30V and 1095 blades but cracked off on the Meadowlark due to more wear/stress compared to the other blades.

This doesn't make a lot of sense though because the Sharpmaker edge burrs should be more durable than a steeled edge after extensive cutting as that has to be all weakened metal, whereas the Sharpmaker had to make some improvement.

I will have to use them and check the edge retention, but the theory definately needs work. If this is right the Meadowlark has better edge retention I will have a handle, if not I will be fairly confused.

-Cliff

 

[Carl64]

Cliff, how well-used is the Meadowlark? I recall someone mentioning initial chipping issues with their byrd knife, which went away after lots of sharpening to get rid of the damaged edge.

 

[WarRaven]

Hhhmm,This would be for the harder steels in particular.

I am being led to believe then that, a Micro-Beveled edge is going to be optimal over a single/angled flat grind then, to aid in prevention of cracking/chipping ect...Is this right?

Cliff i thoroughly enjoy reading your post's, nice work, and thanks for sharing with the greater community, i myself apreciate the efforts.

I guess i should just ask this then, Are there problems with putting a single angled edge of say 15/30 Incl. or less,on the harder steels without edge problems, or issues?



WR

 

[Cliff Stamp]

Cliff, how well-used is the Meadowlark?

Very, has been reprofiled to a near flat grind and sharpened (edge reset) at least two dozen times.

I am being led to believe then that, a Micro-Beveled edge is going to be optimal over a single/angled flat grind then ...

Yes, the forces on a knife are highly nonlinear in distance from the edge thus you need to adjust the edge profile accordingly.

Are there problems with putting a single angled edge of say 15/30 Incl. or less,on the harder steels without edge problems, or issues

Depends on what you are cutting, I run many knives without secondary edge bevels and the edge are ~5 degrees per side. They cut well but you need to be careful not to crack them into metals and torque load them.

Ok I think I have figured out what was going on with the stropping, the S30V and 1095 blades had very thin and acute edges and suffered little wear during the cutting and thus the steeling+stropping was able to reset the edge trivially.

On the Meadowlark, the softer edge with the same profile was more heavily stressed and worn and thus the steeled edge was made of much more weakened metal which broke off when stropping and much more would need to be removed to restore it.

Anyway, that makes sense to me, I have more work planned to test this idea further.

-Cliff

 

[Cliff Stamp]

In my usual timely manner, I did some more work with this recently. I had sharpened an Opinel as I want to benchmark it for some wood/kitchen work as well as repeated some of the recent stock work I have been doing. Ideally to compare it to Alvin's 1095 paring knife because this should isolate the effect of hardness and as well see how it fares against the Mora 2000 as both are cutting standards.

After regrinding there is a large primary burr made up out of junk metal and debris, under magnification it looks like a saw tooth wave. I try some burr removal and it just pushes it around. However on the 0.5 micron chromium/aluminum strop it is very quickly removed and leaves a very fine finish. This is in striking contrast to the behavior of the high alloy stainless as predicted.

-Cliff

 

[lambertiana]

I strop plain carbon steel, S30V, and D2 on a regular basis. The carbon steel gets to an amazing edge very easily. In my experience, with the higher alloy steels like S30V and D2, you have to finish the edge fairly well before you get to the final strop, or it takes a long time. With some knives I finish on X-fine diamond, with some I finish on a succession of increasingly higher grit sandpaper before I go to the final strop.

If you press hard on a strop that has a lot of give to it, or is resting on a soft surface (sometimes even a mousepad is too soft) then you can easily round the edge rather than finish it.