The importance of stropping edge tools

[Yorkshire Sam]

Being an amateur wood butcher, I seldom used to ‘strop’ my chisels and plane irons after sharpening. I have always managed to get my tools sharp enough just using a medium and fine stone and only used to strop when I needed that extra touch, such as when doing a fine joint or paring. That is until recently. Before Christmas I decided I wanted to try my hand at wood carving and have become quite taken with it.
Sharpening carving tools is often just a case of a quick touch up with a strop, unless one is commissioning or resetting a tool. Finding the difference it makes to a finished edge has been quite enlightening and now I always finish an edge tool with a strop.
I wonder how many other people often don’t bother using a strop but manage using just stones?

 

[Racers]

I often throw a strop, and always strop my edges it only takes a second or two and makes a big difference.

Leather and Autosol.

Pete

 

[bugbear]

Being an amateur wood butcher, I seldom used to ‘strop’ my chisels and plane irons after sharpening. I have always managed to get my tools sharp enough just using a medium and fine stone and only used to strop when I needed that extra touch, such as when doing a fine joint or paring. That is until recently. Before Christmas I decided I wanted to try my hand at wood carving and have become quite taken with it.
Sharpening carving tools is often just a case of a quick touch up with a strop, unless one is commissioning or resetting a tool. Finding the difference it makes to a finished edge has been quite enlightening and now I always finish an edge tool with a strop.
I wonder how many other people often don’t bother using a strop but manage using just stones?

I gather the impression from old texts that carvers stropped frequently, and resorted to stones infrequently.
Rouge was their strop dressing of choice.

Carvers need truly sharp edges, both to reduce labour, and because sandpapering intricate work
is practically impossible; the work must be finished from the cut.

BugBear

 

[Corneel]

At first I sharpened on waterstones and didn't feel the need to strop after an 8000 stone, carefully removing the wire edge. Now on oilstones and the strop is an integral part of my sharpening regime.

And indeed you can keep a chisel or gouge sharp much longer when you regularly strop. It does round over the corners a bit though, and I feel that it takes longer to sharpen on the stones after stropping a lot. The bevel does get steeper and it is harder to reach the true edge and raise a wire edge on the lower grinding angle.

 

[Derek Cohen (Perth Oz)]

On plane blades and chisels I finish with green compound on hardwood (not leather). I am not sure whether this is technically a "strop", however I use it as one. I feel that leather can degrade an edge by rounding it over.

Regards from Perth

Derek

 

[D_W]

I always finish with bare leather. When I used really aggressive stones with a tiny particle size, I didn't.

For touch-ups with chisels, I either leave a finish stone and (bare leather) strop out or a jasper. That's usually enough to allow you to start with a sharp chisel and end with one, without chasing an edge steeper like would happen using leather and compound.

 

[D_W]

Addendum to the above - I've experimented with a lot of different sharpening stones - more than $10,000 worth over the last 12 years as it's just a side interest (of course, I didn't keep them all). The shapton 15ks of the world don't need a strop for woodworking, etc, but you do get a good idea of how much a strop smooths the bleeding edge if you try to shave straight off of one. Thinking they were about as fine as it gets, I started shaving with a shapton 15k as a finisher 10 years ago or so and didn't have a good strop yet. I just couldn't figure out why the shaves were so rough. Linen and then leather knocks all of the roughness off. I never shave without stropping a razor now - even if you have a strop with compound, the razor still needs to pass over bare leather after that or the brashness of the edge will be noticed - and that includes graded abrasives at 0.25 and 0.5 micron.

For coarser stones, it's just an assurance that you've gotten the wire edge off. If you sharpen an edge without a strop, you generally find it shaves hair easily on one side or the other. If you strop with bare leather (properly), you'll find that the edge shaves hair pretty easily on both sides. An indication that there is still a tiny burr, and stropping is removing it. Faffing around off of a shapton 15K, but you can do it. If I still used that stone, I'd just make sure the flat face of the iron was the last part I worked - it leaves the clean side of the burr oriented toward the cut.

 

[bugbear]

Addendum to the above - I've experimented with a lot of different sharpening stones - more than $10,000 worth over the last 12 years as it's just a side interest (of course, I didn't keep them all). The shapton 15ks of the world don't need a strop for woodworking, etc, but you do get a good idea of how much a strop smooths the bleeding edge if you try to shave straight off of one. Thinking they were about as fine as it gets, I started shaving with a shapton 15k as a finisher 10 years ago or so and didn't have a good strop yet. I just couldn't figure out why the shaves were so rough. Linen and then leather knocks all of the roughness off. I never shave without stropping a razor now - even if you have a strop with compound, the razor still needs to pass over bare leather after that or the brashness of the edge will be noticed - and that includes graded abrasives at 0.25 and 0.5 micron.

Could you clarify - are you asserting that stropping is a process different in kind to using ever finer stones, that undressed linen or leather carry yet finer abrasives than the finest stones and dressing compounds, or something else entirely?

BugBear

 

[Trafalgar]

Stropping on something charged with a compound is really just fine honing. Stropping on your hand, blue jeans, brown paper sack, untreated leather, etc. is stropping per se -- at least in this silly person's opinion. That said, I often 'strop' on hard rubber with AlOx powder -- it's basically an extremely fine honing stone, though I tend to fall in and out of love with this routine -- can be a little persnickety, or what I perceive to be a little persnickety at that moment in time.

 

[D_W]

Addendum to the above - I've experimented with a lot of different sharpening stones - more than $10,000 worth over the last 12 years as it's just a side interest (of course, I didn't keep them all). The shapton 15ks of the world don't need a strop for woodworking, etc, but you do get a good idea of how much a strop smooths the bleeding edge if you try to shave straight off of one. Thinking they were about as fine as it gets, I started shaving with a shapton 15k as a finisher 10 years ago or so and didn't have a good strop yet. I just couldn't figure out why the shaves were so rough. Linen and then leather knocks all of the roughness off. I never shave without stropping a razor now - even if you have a strop with compound, the razor still needs to pass over bare leather after that or the brashness of the edge will be noticed - and that includes graded abrasives at 0.25 and 0.5 micron.

Could you clarify - are you asserting that stropping is a process different in kind to using ever finer stones, that undressed linen or leather carry yet finer abrasives than the finest stones and dressing compounds, or something else entirely?

BugBear

What charlie said - linen and leather do not have anything in them that is as hard as hardened steel. Linens were treated with something that had mohs abrasive about 3, and they had some kind of waxy binder in them to hold it to the strop. You could linen a razor for a week and probably not get much metal off of it. Leather - same. Horse butt strips probably have some silica in them (they are scratchy at first, very much so sometimes), but soon become tired and slick and then no longer scuff an edge. Bovine leather of good quality is the same, no real abrasive action. Using linen and leather creates a smoother edge than anything because it doesn't raise a wire - smoother even than graded iron oxide (.09 micron), though going the graded iron oxide route then to linen and leather creates an uncomfortably sharp edge. Hard stropping will knock some of the brashness off - it's too small to see, so I don't know why. I would suspect that the leather is wearing the edge just a little, same with the linen, but it's so little that it can only work at the very edge, and just skates on the bevel of anything and never appreciably steepens something unless you "roll" an edge (drag it across a strop at a steep angle - and that actually bends the edge rather than abrading it).

As charlie said, the rest of the loaded strops are just soft hones - they abrade metal and will never stop if there is uncovered abrasive on the surface.

It's hard to get across to the shaving community that linen and leather was used without much abrasion for straight razors - that the people who used those two things knew what they were doing and weren't just a bunch of dumb antiquated oafs. It's the belief of a lot of people on those forums that the modern abrasives make for a superior edge (which wastes expensive razors) and that we should be honing a bunch of material off razors and using abrasive pastes very regularly. Different issue than woodworking sharpening, but same notion that the modern stuff offers some kind of advantage and that craftsmen would discard their natural stones and india stones if they'd have had access to shaptons or some other goofiness (the "people were dumber and tougher back then" theory - they were probably just tougher).

 

[Corneel]

I have no idea about straight razors. I use disposable Gilettes and use them about 20-30 times or so. Shaving twice a week, so they have to cut some real hair.

Anyway, I find that a new Gilette has a very rash feel to it, like David describes above. After two or three shaves the feel is much nicer. I guess that is some kind of stropping too, with the strop being the skin of my face.

On my woodworking tools I use a hard leather strop glued to some wood with a little bit of autosol. I had trouble to feel any effect using a bare strop. Maybe I should try again now I have some millage on my stropping technique. The loaded strop certainly makes the edge quite a bit sharper even after a translucent Arkansas.

 

[ED65]

I don't strop every edge when I create it, but I do usually maintain all edges by stropping (loaded strop) so eventually everything gets stropped and is kept up that way as long as possible.

If I do need to hone properly for most planing I now skip stropping because I tested and couldn't notice any increase in resistance and the surface quality is perfectly fine for me straight from my finest oilstone or my 1000# diamond plate. Chisels I almost always strop because they need to be sharp as poss.

Apart from the finer edge I think stropping is valuable because it's forgiving of a bit of sloppiness in technique, as most are guilty of early on. Getting a super-refined edge on stones is possible of course but it's easier doing it on a loaded strop for the learner and usually much faster, at least it is compared to most sharpening on ultra-fine stones that I've seen demonstrated online. Many guys using a succession of stones up to 8k, 10k, 15k or even higher are reaching for stone number two or three when the strop dude would already be back at work!

 

[bugbear]

OK. Dave and Charles have both talked about stropping (with an implied "real stropping") not being an abrasive process.

But then, neither is driving a car, or fermenting beer.

So, as a second request for clarity, would either of you two expert gentlemen care to tell us what real stropping is, and how it effects or manipulates an edge?

BugBear

 

[Trafalgar]

In a woodworking context, and in my view, all it does is remove rag -- the last shards of the burr -- and that's it. It if smooths or contours the edge in any way that's not stropping, that's back to honing. Consistent with this view is stropping on one's hand. Clearly all that would do is remove detritus from the edge, ditto Kraft paper, blue jeans, etc. A swipe through end grain pine, in my case the 2x6 boards on top of my 'sharpening' bench, does the same thing. Not advising that somebody rip a large burr off the edge by its roots. It needs to be flexed and polished as far as your particular system will take it -- those with very fine media don't need to strop at all, in the sense of my definition in this reply.

Get this: http://toolsforworkingwood.com/store/item/NO-SVIDEO-OIL

 

[D_W]

If I posted my thoughts, they'd just match Charlie's.

 

[Derek Cohen (Perth Oz)]

This is the way I see it ...

The premise for using progressively finer media for honing is, as we all know, that the steel becomes polished to progressively smoother surface. Some like to see a mirror at the end, but not all media do so. Regardless, it is the "smoothness" of the edge that is associated with "sharpness".

As the edge becomes smoother, the wire that forms becomes smaller. Ultimately, the wire is so small that it comes off with little effort (some steels, such as A2, are more tenacious ar holding the edge - presumably because the grain is coarser).

In an ideal world, the wire would become so small that it would become irrelevant rather than need to be broken off. The problem with breaking off a larger wire is that it can tear and leave a jagged edge. This effects the way a blade cuts.

Stropping with an abrasive, such as green compound, combines both an ultrafine finish together with a gentle removal of the wire. I see this as the best of both worlds. I also use the green compound on hardwood, rather than leather, as this is better able to preserve the honed angle. Leather compresses, and this will alter the angle and, in fact, theoretically, if the steel is being moved rather than abraded, this could create another wire.

Regards from Perth

Derek

 

[Derek Cohen (Perth Oz)]

This is the way I see it ...

The premise for using progressively finer media for honing is, as we all know, that the steel becomes polished to progressively smoother surface. Some like to see a mirror at the end, but not all media do so. Regardless, it is the "smoothness" of the edge that is associated with "sharpness".

As the edge becomes smoother, the wire that forms becomes smaller. Ultimately, the wire is so small that it comes off with little effort (some steels, such as A2, are more tenacious at holding the edge - presumably because the grain is coarser).

In an ideal world, the wire would become so small that it would become irrelevant rather than need to be broken off. The problem with breaking off a larger wire is that it can tear and leave a jagged edge. This effects the way a blade cuts.

Stropping with an abrasive, such as green compound, combines both an ultrafine finish together with a gentle removal of the wire. I see this as the best of both worlds. I also use the green compound on hardwood, rather than leather, as this is better able to preserve the honed angle. Leather compresses, and this will alter the angle and, in fact, theoretically, if the steel is being moved rather than abraded, this could create another wire.

Regards from Perth

Derek

 

[bridger]

The electron microscope pictures at the science of sharp blog seem to indicate that even plain leather stropping is removing metal. I don't think that there is a hard line between honing and stropping. Personally I make the distinction at the difference between rigid and cushioned abrasives.

 

[bugbear]

In a woodworking context, and in my view, all it does is remove rag -- the last shards of the burr -- and that's it. It if smooths or contours the edge in any way that's not stropping, that's back to honing.

OK; we now have a definition of what stropping does; it removes the last traces of the burr, but (again defining what stropping isn't) not by abrasion.

So what is the mechanism of stropping, and (for bonus points) why is this action different in linen versus leather?

I'm aware that I am (in effect) asking "what is stropping" again and again, but since I keep failing to get a concrete answer, I'll just keep asking.

BugBear

 

[PAC1]

As an apprentice, I was taught to strop (as in removing the last traces of a burr) on the palm of my hand. You have to appreciate that those hands were as tough as leather from years of working wood. Also for blades narrower than half inch you had to use leather anyway as it was too dangerous to strop on your hand. Whilst Blue Jeans are a good option I have seen an edge go straight through them so I would say relatively new blue jean only. I always assumed that by removing those traces of burr it meant they could not be pushed onto the edge and damage the edge when you start cutting wood. Whether there is any actual sharpening going on I very much doubt. With carving tools it is a different process of actual abrasion.