The importance of stropping edge tools

[D_W]

Yes of course but it's hard to imagine linen providing a similar phenomenon but I suppose the photos don't lie.

The treatment applied to old linens makes them hard and smooth and stiff without being scratchy. They bear little resemblance to linen found in clothes, old napkins, etc.

 

[D_W]

As wonderful as the information is on scienceofsharp I think we need to be realistic about what the take-home message here is as far as how we would typically strop. When I strop I get a noticeable improvement in shine, and polishing is generally understood to be largely an abrasive process (material removal).

Now despite what the above shows about plastic deformation is there much of that happening stropping the way we do? Well that's going to depend.

I don't know about anyone else here but I'm not stropping 100 strokes every time! And I'm not using a very firm unloaded strop. Don't have time for that kind of lark. I'm doing less than 30 strokes on a loaded softish strop. So as far as my experience of stropping goes I'm confident it is nearly entirely an abrasive process, what about you?

10 with pressure is fine for tools. 30-50 with light pressure is typical for straight razors. Low reps and heavy pressure damages razors because the angle is too acute.

 

[Trafalgar]

Yes of course but it's hard to imagine linen providing a similar phenomenon but I suppose the photos don't lie.

The treatment applied to old linens makes them hard and smooth and stiff without being scratchy. They bear little resemblance to linen found in clothes, old napkins, etc.

What you are describing might be a reason linen actually abrades rather than deforms. Not debating this though just thinking aloud. In my mind's eye I'm juxtaposing a scraper burnisher and a barber's linen strop and not coming up with them having the same effect on steel. That said, there are the photos from the referenced blog. Obviously if they do have the same effect then linen is the more subtle of the two.

 

[D_W]

Yes of course but it's hard to imagine linen providing a similar phenomenon but I suppose the photos don't lie.

The treatment applied to old linens makes them hard and smooth and stiff without being scratchy. They bear little resemblance to linen found in clothes, old napkins, etc.

What you are describing might be a reason linen actually abrades rather than deforms. Not debating this though just thinking aloud. In my mind's eye I'm juxtaposing a scraper burnisher and a barber's linen strop and not coming up with them having the same effect on steel. That said, there are the photos from the referenced blog. Obviously if they do have the same effect then linen is the more subtle of the two.

The abrasive in the linen is about mohs 3 (Some are made without the abrasive at all). It works like a stiffer strop and will do faster work to realign an edge, but it won't bring back an edge that is truly worn or that was sharpened incorrectly (if it moves metal like a knife steel, it would be less and slower, but maybe along the same principle). Over 6 or 7 years used weekly (Only leather is used daily), mine hasn't turned gray with metal, so very little metal removal with several thousand laps.

Probably not good to compare with tools since so little abrasive wear happens on a razor, and the vintage process is to preserve the very edge when honing, and baby it with non or minimally abrasive mediums. Compared to honing the edge off with tools. The edge on my daily razor is about 3 years old now, and the stone is used just to make sure the bevel isn't rounding at all - about once every 6 months. The instructions with the old hones dictate minimal use to protect the edge, and are thus fairly coarse alumina - 1200f or so. Instructions say something like 4 passes and then test shave, only using more if the edge is still blunt.

The methods advocated on shaving forums involve arduous routines with progressive fine abrasives creating a transient edge that needs to be refreshed bi-weekly or so. Not a lot different than what happens with woodworking- modern dogma, I guess.

 

[ED65]

If you know of any evidence that shows stropping is an abrasive process, lob it into the mix and let's assess it.

I'm using a loaded strop remember. Quite evidently once you're using a loaded strop, treated with a polish or compound of some sort, the process is at least in part abrasive. There are images showing that abrasion occurs both online (on scienceofsharp, as well as in Brent Beach's microscope photos) and in one or two books if you need to see it to believe it occurs, but the colouring of the strop is evidence enough by itself.

FWIW long before this I'd taken it as a given that traditional stropping moved steel in some way because there is and has always been so much talk about realignment of the edge, or words to that effect. Even if there were no images that showed something of this is occurring there was much user experience that strongly supported that interpretation, which taken together with the evidence of so little colouring of the strop surface pretty conclusively proved it AFAIC.

 

[D_W]

I would encourage everyone to take up straight razor shaving, because you get a better sense of what's going on at an edge and shortcomings are easily felt on your face.

I was surprised, as someone who was perfectly competent at sharpening woodworking tools, that razor sharpening was not easily perfected. Doing it the old way still turns out to be the best way, but takes a couple of months or more to perfect and be sure that you'll get a good edge without having to backtrack and retrace steps.

Point of it all is it gives you a way to feel what's going on with stropping, because it's just about impossible to see what's going on. (And there's a good chance you'll enjoy the process of maintaining the razor as well as shaving with it).

 

[Trafalgar]

The Yang to go with the Yin I guess, and a perennial favourite (love the "u"):

http://www.richardjonesfurniture.com/Ar ... ening.html

And my favourite Richard Jones project of all time. Scroll down to see his brilliant pre-build illustrations:

http://www.richardjonesfurniture.com/Ca ... edore.html

 

[D_W]

Drawings are great. Can't say I favor the final result much, perhaps because my son is in a school with lots of rainbow furniture. Not as well made, of course. I believe richard suggested that piece was mostly made by cnc, unless he was just trying to make a point in the hand tools section of woodcentral.

The article says use a stone and strop with something, which is pretty much what we're talking about. I didn't reread the article, but I remember it suggesting a red king stone, which explains the suggestion of emery flour. I doubt much other than jack planing is done straight off of a red brick.

Still would suggest straight razor shaving, as it's illuminating, and it doesn't follow the ridiculous modern model of overpriced disposable razor parts.

 

[Andy Kev.]

This guy covers it:
https://scienceofsharp.wordpress.com/20 ... opping-do/

That suggests to me that stropping is more a burnishing process (plastic deformation - moving metal around) rather than an abrasive process (removing metal). Putting it another way, the main effect seems to be slightly reshaping an edge by deforming metal to where it's wanted to make a better cutting edge, rather than by abrading it to form a new edge in new metal.

From a purely personal observational point of view, that rather confirms what I find when using a slate polishing stone. There seems to be only slight metal removal, but when I treat tool edges by only trailing them on the stone (rather than the usual honing practice of back-and-forth), I end up with edges that seem sharper than almost any other way I've tried. I've noted the same effect on an ultra-fine ceramic stone too. That practice seems to both remove the wire edge from the main honing stone (fine India in my case, or medium ceramic in the past), and burnish the honed edge to a better 'finish' than the honing stone leaves.

That effect does not happen if I use the same back-and-forth technique on the slate as I use on the India, or at least, not as quickly.

I've no proof of this whatever, but my suspicion is that leather, palm of hand, piece of hardwood dressed with compound or undressed, or polishing stones, all do the same thing - burnish rather than abrade.

I suspect that there's an awful lot in that and I'm tempted to believe that the notion of e.g. the palm of the hand giving the final touch is not a bit of baseless fantasy but rather the result of somebody noticing that it produced a definite effect. However, the key question must surely be, "How long does the effect last?" If this final touch, which involves relatively little mechanical force, gets the wire off followed by a hint of beneficial deformation, how many strokes of a blade on wood will cancel it out? The freshly sharpened and stropped blade is no doubt optimal but I can't imagine that it does anything other than quickly go to "normal" (i.e. perfectly satisfactory) sharpness, depending on the species of wood worked. Of course it makes sense to start from the best sharpness you can achieve. It's just that I suspect it is not available to you for very long. Also "best sharpness" might be more than enough on woods which plane easily but just about enough on some of the more outrageous tropical woods.

 

[Corneel]

Just a theory, I can't prove it in any way. But when a strop makes the edge smoother, less jaggedy, less wire remaining, less sharp nicks, then it might help to increase the longevity of the edge and promotes ideal wear which is a rounding of the edge, instead of sudden chips.

 

[Derek Cohen (Perth Oz)]

Kees, I don't buy that. In effect you are saying, the better edge is one where the cutting angle is increased - in other words, a higher secondary micro bevel. That is not going to produce a sharper edge, although it may be a more durable edge.

This is the reason I switched from leather to hard wood.

Regards from Perth

Derek

 

[Trafalgar]

Where did Kees say anything about increasing the angle?

 

[Derek Cohen (Perth Oz)]

Charles, my bad .. you are right. I misread that. Apology Kees.

Still, my point about raising the cutting angle remains. Any thoughts?

Regards from Perth

Derek

 

[Trafalgar]

Raising the cutting angle won't make an edge sharper, though proponents of back beveling, Ruler Trick(ing), etc. would probably disagree.

A lift on a strop, even a charged strop, at a slightly higher angle for just a couple of passes helps pull off rag and put a little polish right on the edge and does it likely without changing the angle -- this will make an edge sharper IMO. If over-baked the geometry starts to change; you'll have a sharp edge, but at an angle that might affect how the tool works and not necessarily in a good way.

Interesting to see Hayward writing about a "sash pocket chisel" in his book on woodworking tools -- a very low ground knife-edged chisel used to cut the weight pockets in softwood window jambs (access pockets to re-cord the sash weights). I guess if one's job was to cut these all day long then you figure out a tool set up that does it best. Basically the same as a carver's straight chisel.

 

[Phil Pascoe]

It probably helps make it sharper - but raising the angle isn't why.

 

[Trafalgar]

It probably helps make it sharper - but raising the angle isn't why.

Yep. A sharp tool but at a higher perhaps unintended angle.

 

[D_W]

Just a theory, I can't prove it in any way. But when a strop makes the edge smoother, less jaggedy, less wire remaining, less sharp nicks, then it might help to increase the longevity of the edge and promotes ideal wear which is a rounding of the edge, instead of sudden chips.

Kees,are you talking about a plain strop or a loaded strop?

I've noticed that a strop with anything even similar in hardness to steel will cut a fair amount off. From trying iron oxide pigment on a paddle strop, it turned black very quickly. I would've thought it would only burnish.

I agree with your thoughts on a plain strop and with minimal strokes on a loaded one.

I think you can still roll an edge, though, even on a plain strop. It's interesting enough to try next time I'm in the shop to see if a much less acute tool edge will roll in a way that affects sharpness. On a razor, a roll of the edge sends you back to the fine hone, but it's not something that happens after you have a little bit of experience. Effective angle on a razor is about 18 degrees.

 

[Phil Pascoe]

Actually, if the ruler trick works, it would be logical to presume stropping the back of the blade would as well. Does anyone do it?

 

[D_W]

Actually, if the ruler trick works, it would be logical to presume stropping the back of the blade would as well. Does anyone do it?

I do. You have to work the wire edge back and forth to remove all of it, so you have to work the back some number of strokes. I do about 1 on the backside for every three on the front.

 

[memzey]

I always strop the face (non-bevelled side), flat against the media, as well as riding the bevel on the strop. I go from one to the other a number of times. My thinking is that by doing so I'm weakening and eventually causing the remnants of the wire edge to fail in a clean break. I've been reading this thread with interest and despite the many fascinating revelations it contains, I still think what I'm doing works because of why I think it works. Am I wrong? BTW I use a piece of flat mdf loaded with a bit of autosol as a strop.