Is it possible to sharpen knives by only stroping?

[standy99]

Butcher here and can sharpen pretty good. Only use a wet stones and a steel most of the time but have a few strops for razors only. ( have a multitude of different grade steels collected over 50+ years, some of my fathers )

Strops have their place but most people always forget a good steel.

Stone
Steel
Strop

Working with knives all day I would sharpen every morning and maintain the edge with a steel for the rest of the day ( usually 2-3 different grade steels and types )

Will have to take some pictures one day of how much steel gets worn away in a butchers knife over a few months. I have two of the same knives in the kitchen at the moment and side by side they look like two completely different knives as one blade is half worn from sharpening.

[Albatross]

For perspective, a .25 micron strop is approximately 98,000 grit. I don't know of any stones that even come close. When I want a coarse edge, strops will allow me to do things I can't with my stones, like keeping the edge "toothy", while being able to push cut like a polished edge. Stones remove too much steel to keep that toothy aggression, while pushing past 18k grit.

Necessary? No.
Preference? Yes.
Higher achievable sharpness? Yes.

If anyone is taking more than 5 minutes to strop, they are either being meticulous or doing it wrong. I brought Rex 45 from being unable to cut paper, to shaving sharp, with a 1 micron strop, in less than 5 minutes. K390 took even less time than that.

I wonder if some who are opposed to strops, are basing their preference, at least partially, on the old compounds everyone used to swear by. I used green and black compounds for years, but the diamond sprays work so much better. They are faster and seem to give a more crisp edge.

The highest grit diamond plate I have is about 1800. The highest alumina stone I have is the Spyderco ultra fine. None of the fancy 4k + grit diamond or CBN stones. No high grit whetstones. I can get knives very sharp with the ultra fine or high grit diamond, but at a certain point, it becomes faster and more efficient with a strop. I can spend 10 minutes on a finishing stone, or 3 on strops, and still end up with a higher level of sharpness. A 98,000 grit strop will always provide a sharper edge than the ultra fine stone alone, assuming it's done correctly.

As far as steel hones go, the strops I use have diamond compounds on them. They straighten edges and remove a very small amount of metal. You can see it on the strop, but it's nearly impossible to notice any steel missing from the edge. For my uses, a steel isn't necessary, since it wont offer any benefit over my strops.

Straight razors are not exclusively maintained by strops. They need to be sharpened, just like any other blade. Stropping is just keeping the sharpness high. It's recommended that Japanese whetstones are used for sharpening straight razors, with a minimum finishing stone of 6k. Many go past 12k, some even go to 20k or higher.

[ZrowsN1s]

Darby has a good point. Technically I'm not stropping, I'm free hand sharpening with an ultra fine CBN emulsion on a soft medium (leather). But I think these days when people say 'stropping' this is what they mean. I don't think a lot of folks are doing bare leather when they say stropping.

I also think that like free hand sharpening, learning to strop/sharpen with soft media is a skill that takes practice to master and get good at. I think a lot of what divides people who like strops and people who don't is how good at it people are. If you don't have good results, you probably won't like it as much as the people who do.

How much you use your knife is also a factor. Say for example if you use your knife hard enough to deform the edge, or wear all the teeth off it. Stropping wont help much. Stropping is for knives that have a good apex but misaligned teeth. Or for polishing the teeth at the edge. A coarse stone finish with polished teeth can give interesting results.

And as far as weakening the edge through stropping, this can absolutely be a problem, especially for beginners, like free hand sharpening, once you develop a consistent angle, a feel for the media and a light touch, this becomes much less of an issue. As others have said with a light touch and small adjustments you can straighten a bent paper clip with no problems, make large repeated bends and it will break.

[aaronkb]

In theory you could although enough time, if you have nothing to do for days and you’re impervious to tendonitis.

[Albatross]

Darby has a good point. Technically I'm not stropping, I'm free hand sharpening with an ultra fine CBN emulsion on a soft medium (leather). But I think these days when people say 'stropping' this is what they mean. I don't think a lot of folks are doing bare leather when they say stropping.

I also think that like free hand sharpening, learning to strop/sharpen with soft media is a skill that takes practice to master and get good at. I think a lot of what divides people who like strops and people who don't is how good at it people are. If you don't have good results, you probably won't like it as much as the people who do.

How much you use your knife is also a factor. Say for example if you use your knife hard enough to deform the edge, or wear all the teeth off it. Stropping wont help much. Stropping is for knives that have a good apex but misaligned teeth. Or for polishing the teeth at the edge. A coarse stone finish with polished teeth can give interesting results.

And as far as weakening the edge through stropping, this can absolutely be a problem, especially for beginners, like free hand sharpening, once you develop a consistent angle, a feel for the media and a light touch, this becomes much less of an issue. As others have said with a light touch and small adjustments you can straighten a bent paper clip with no problems, make large repeated bends and it will break.

I agree 100%. It took me longer to be able to strop properly, than it took to be able to sharpen properly. Part of that was a poor quality strop, poor quality compounds, and poor technique. Since then, I've found what works for me, and consistantly have the best results I've ever had.

Anyone who has a ZDP-189 blade, which doesn't strop, is leaving edge retention on the table. Cedric and Ada did some testing on different finishes. ZDP loves a high polish. I'm not sure where the point of diminishing returns is, but its sub .5 micron, or more than 46,000 grit.

[Wartstein]

I think the context was either getting a knife super sharp, or it's just someone's preference. For a beginner, it's easier to get a knife sharp, if they use a strop to finish things up. It's easier to fully remove a burr on a strop, than it is on a stone. At least it is for me, but I've been using strops for a long time.

Either way, strops, despite fatiguing the steel a bit, are fantastic for maintaining your edge between sharpenings.

The "easier to remove a burr on a strop" or to "being able to better feel it" - things are new to me and very interesting. Thanks!

Will have to try that (I use my strop very seldom); Does this work on both loaded and unloaded strops?

[Albatross]

I think the context was either getting a knife super sharp, or it's just someone's preference. For a beginner, it's easier to get a knife sharp, if they use a strop to finish things up. It's easier to fully remove a burr on a strop, than it is on a stone. At least it is for me, but I've been using strops for a long time.

Either way, strops, despite fatiguing the steel a bit, are fantastic for maintaining your edge between sharpenings.

The "easier to remove a burr on a strop" or to "being able to better feel it" - things are new to me and very interesting. Thanks!

Will have to try that (I use my strop very seldom); Does this work on both loaded and unloaded strops?

You always have an open mind Wartstein, that's a very good thing.

You will be much better off with a loaded strop.

If your strop has begun drying out(noticeably stiffer leather) try working in a little mineral oil. That will make the leather more supple. I only say this, because you mentioned not using yours much.

Good luck and let us know how it goes.

[GarageBoy]

Do traditional Japanese cutlers use strops? Or do they mainly use super fine stones to do the same thing?

[Wartstein]

The "easier to remove a burr on a strop" or to "being able to better feel it" - things are new to me and very interesting. Thanks!

Will have to try that (I use my strop very seldom); Does this work on both loaded and unloaded strops?

You always have an open mind Wartstein, that's a very good thing.

You will be much better off with a loaded strop.

If your strop has begun drying out(noticeably stiffer leather) try working in a little mineral oil. That will make the leather more supple. I only say this, because you mentioned not using yours much.

Good luck and let us know how it goes.

Thanks for your kind words and I hope I do have an open mind... would be a good thing especially for ME, since there is so much I don´t know yet- generally, and compared to many others on this forum. :)

/ Tbh, I never used my strop loaded, but always just the leather itself. While that HAD a somewhat noticeable effect on sharpness indeed (at least on steels like VG10), it was very minor and not really worth the effort.
But my strop actually came with some kind of compound which I never applied, but still can do so and see how this will work out!

[bbturbodad]

Although this doesn't really address OP's question, I'll throw this out there in regards to a 'stropping' technique I've been playing around with lately that has been giving me good results. After sharpening to a course finish, I use a fine stone and make a few stropping passes which gives me a semi-polished toothy finish that is both aggressive when using a pull cut and still able to smoothly push cut. In addition to the versatility of the finish, it's quick because only one stone is used for sharpening and the stropping is done with only 3 alternating passes on the fine stone which also has the added benefit of less risk of rolling the edge than a soft strop.

For traditional stropping I like basswood (good hardness to compound absorption ratio) with a CBN or diamond compound so that it cuts the steel vs just burnishing.

[Cambertree]

Do traditional Japanese cutlers use strops? Or do they mainly use super fine stones to do the same thing?

Not that I’ve seen. The traditional knifemakers I saw in Sakai, Seki and Sanjo just finished with fine Shiageto stones.

A bladesmith I spoke with at the Iwasaki straight razor (kamisori) forge in Sanjo, finished with a pocketsize piece of natural finishing stone held between thumb and forefinger, honing the blade in little circular motions.

[Cambertree]

Another angle to ‘sharpening by strop’ which doesn’t seem to have been explored a great deal is using relatively coarse cutting compounds.

I recall Cliff Stamp did some experiments with 220 grit valve grinding compound on cardboard IIRC, which worked ok, and removed metal and reshaped the edge in a similar way to a coarse stone, but with more natural ‘convexity’.

I recently experimented with 80 micron diamond paste on balsa, and it also worked well - although this was on an edge straight off the 400 mesh Sharpmaker diamond rods.

A light strop with coarse paste seemed to align the diamond stone ground edge and yet retain that aggressive bite.

[Bloke]

Another angle to ‘sharpening by strop’ which doesn’t seem to have been explored a great deal is using relatively coarse cutting compounds.

Indeed, Camber!

I maintained my ZDP-189 Stretch blade with 5μm diamond paste on balsa for a while and you could feel and hear it cut.

However, "strop' is quite subjective and ultimately even unloaded strops abrade so theroticaly you could certainly sharpen with a strop though I doubt edge trailing sharrpening would give you the best edge retention. By that I mean you'd never actually cut the burr, you'd pull it straight and your blade would be sharp but only till the burr folded or broke away.

Just my $AU0.02c worth. :)

[marshmallow]

In regards to stroping, what is the actual mechanism on why stroping on the leather sharpens the blade? Is it the friction the blade makes on the leather that heats the edge to soften it?

[GarageBoy]

Gonna need way hotter temperatures than you get from stropping to soften steel - you're bending material back after it has rolled or breaking off loose burrs with no compound

[Cambertree]

Another angle to ‘sharpening by strop’ which doesn’t seem to have been explored a great deal is using relatively coarse cutting compounds.

Indeed, Camber!

I maintained my ZDP-189 Stretch blade with 5μm diamond paste on balsa for a while and you could feel and hear it cut.

However, "strop' is quite subjective and ultimately even unloaded strops abrade so theroticaly you could certainly sharpen with a strop though I doubt edge trailing sharrpening would give you the best edge retention. By that I mean you'd never actually cut the burr, you'd pull it straight and your blade would be sharp but only till the burr folded or broke away.

Just my $AU0.02c worth. :)

That’s interesting Bloke. Yeah, I think the availability of diamond and CBN compounds have changed what a sharpener can expect to achieve with stropping, especially on high carbide, high wear resistance steels.

There’s some interesting comparison pics on the Scienceofsharp website showing the difference between edge trailing and edge leading passes. Funnily enough it was edge trailing finishing strokes that gave the most acute and cleanest apex. Todd Simpson, the writer of the blog developed a technique of creating a ‘foil edge’ then stropping it with hanging denim and aluminium oxide paste, to a centred apex.

Of course this was on a straight razor made out of simple carbon steel. I’ve tried it on other steels and it doesn’t seem to work as well, nor would it probably be as durable for folding knife usage.

In regards to stroping, what is the actual mechanism on why stroping on the leather sharpens the blade? Is it the friction the blade makes on the leather that heats the edge to soften it?

Animal hides have silica particles in them. The quantity will vary depending on various factors, including diet and the terrain the animal lived in.

I think bare leather strops are more effective for softer, simple carbon steels. Using compound is advisable for many of the steels that Spyderco offer.

I sometimes use a couple of passes on a bare roo leather strop to finish with, but that’s more to wipe off any residual paste from the last loaded strop.