Does stropping actually sharpen?

Django606

Django606

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I have a question. Instead of sharpening your knife after some light use, can you just strop it? I know the sharpening creates a burr, stropping will remove the burr, blah, blah, blah. What does stropping do if you have already taken the burr off? Does the burr reform once you start cutting things with the knife?
 
It would depend on what you stropped it with. You can strop a knife on abrasives which range from very coarse to very fine. Frequently stropping is associated with very mild abrasives such as plain leather, cardboard or just paper or even skin, these have little to no significant abrasive ability but can align slightly a deformed edge. If this is the goal then a smooth steel is a much more efficient choice. A burr doesn't reform with use, but edges can deform, usually this is often the critical form of blunting. Leaving this weakened metal on the edge is usually not the optimal sharpening responce however as it will go blunt much faster than it did before.

-Cliff
 
You can form or remove a burr by stropping. You can strop with leather, cardboard, wood, paper, canvass, silk, even with regular sharpening stones. If it's in this universe, you can strop with it and someone here probably has.

Most of the time, when we think of stropping, it's done on leather or carboard and two things are often accomplished:

The edge is pushed from a crumpled state back into an aligned state (like the way it's easier to get a papercut with a fresh piece of computer paper than with a crumpled-to-heck one) and the very edge gets cut away (still in an edge shape) to expose a fresh and sharp layer of steel.

If the edge is pushed back into shape after cutting had orginally pushed it out of shape, the edge will be weaker than it had been and can flop out of place (roll to one side as a burr or like a burr) easier with more of the same type of cutting that originally dulled it. You can reduce that effect by stropping with a more aggressive abrasive so that you're setting the edge by removing fatigued steel more and smushing steel less.
 
Django606 said:
I have a question. Instead of sharpening your knife after some light use, can you just strop it? ...
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Not only can you, but you SHOULD do so. Don't be sharpening the steel away excessively... get it sharp and strop regularly.

JMHO
 
So after light use, is it ok to strop even if it is only on cardboard?

The problem is, I like a slightly toothier edge - one that is better at slicing. I've noticed that I cannot slash cut paper at all after extensive stropping. What do I do if I want to remove the burr, but keep the knife with a toothy edge? Or is the burr the toothy edge? Do I just strop to a lesser extent?
 
Stropping tends to aid push cutting and diminish slice ability. Burr removal on some knives can be a total bear. Of course the absolute best solution is not to form a burr in the first place. Easier said than done of course.

Burr removal methods:
1. Chase it from side to side. Keep dropping grits and eventually it will disappear. (I hope.)
2. Triple the angle and cut it off. Then polish out at smaller grits at the original angle. If a burr forms during this again triple the angle and cut it off.
3. Pull the edge "lightly" through the end grain of a piece of wood.
4. Back stroke on a piece of sand paper on glass at a high angle. Same effect as # 2.
5. Cut a piece of cardboard. Same effect as drawing through the end grain of piece of wood but the cardboard tends to smooth the edge rather just breaking off the burr. It's "duller" but the burr is gone and the edge feels and looks smoother. Again polish out at smaller grits.
6. Keep sharpening until you reach the grit you want to stop at and apply a micro-bevel. This often gets rid of the burr. A lot of times the real purpose of a micro bevel is burr removal to my thinking. I've never run "scientific" tests to verify that micro bevels, single or multiple truly help "sharpness" or edge retention. It seems to do both and that is supposedly the rational behind them but I've never proven or disproven it.

As an aside, in hand sharpening microtome knives I never did put on a microbevel and these are the sharpest edges I've ever attained. They aren't "strong" but they are "sharp".

Teeth or micro-serrations (or serrated edges) do cut more agressively. Try cutting wet hemp rope with a 600 grit polished edge and then cut with a 220 grit edge. The 220 grit will be much more efficent.

I've gone so far as to polish/strop out to 0.5 micron. Then when every thing is beautiful. Go back and touch the blade with a tri corner file every 1/2 inch. Just a light touch, don't bear down and "pull".

Match the edge finish to what you intend to do with it. Delicate work can use a much finer edge and stropping is one way to get that. Whacking through wet rope or zipping through seat belts you want a much more agressive edge. That's to my thinking anyway.
 
Django606 said:
The problem is, I like a slightly toothier edge - one that is better at slicing.
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Me too. I have wondered if stropping positively or negatively affects a toothy edge. Since barbers, at least in the past, are well-known for stropping razors I would think that stropping would have a negative affect on a toothy edge.

What do I do if I want to remove the burr, but keep the knife with a toothy edge? Or is the burr the toothy edge? Do I just strop to a lesser extent?
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The burr is not the toothy edge. It's metal which has been removed from the extreme edge of the knife and lets you know that further metal removal is not necessary.

My understanding, as QuietOned pointed out, is that to get a more toothy edge you sharpen with a coarser grit. The coarser the grit, the more toothy the edge, and vice versa. Joe Talmadge's excellent "Sharpening FAQ" explains this very well.

I question whether it's a good idea to use leather to remove burrs. Getting tiny particles of steel in leather or other stropping material doesn't sound like a good thing.

I thought that steeling pushed metal back and re-aligned the edge and stropping was more for polishing the edge but now it sounds like stropping does the same thing as steeling, just uses different materials. Can anyone clarify this?
 
Say I sharpen a knife on the Sharpmaker, a burr forms, and I strop it until the burr is gone. If I do like two more swipes on each side AFTER stropping, will it put a toothy edge back on the knife, without creating a burr again?
 
Django606 said:
What do I do if I want to remove the burr, but keep the knife with a toothy edge?
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Remove the burr on the stone.

Mtn Hawk said:
I have wondered if stropping positively or negatively affects a toothy edge.
Click to expand...

You can strop on really coarse abrasives or really fine ones, really fine ones will gradually polish away any micro-serrations left by a coarse stone.

...it sounds like stropping does the same thing as steeling, just uses different materials.
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If you strop on something like plain leather or cardboard the level of abrasion is really light and it will mainly be alignment similar to a smooth steel but far less dramatic.

-Cliff
 
I thought that when you sharpen the burr on the stone, it just gets pushed over to the other side? Not sure if I'm right about this, but theoretically, when you sharpen on the Sharpmaker, alternating sides every swipe, doesn't the burr just keep going from side to side?
 
That can be true if the stone is too fine. A medium to coarse grit stone, holding an angle a bit higher than the edge is actually ground at will remove the burr. On the Sharpmaker, the white stones will do little to remove the burr, just pushing it around as you describe.
If you're looking to just realign and touch up the edge, steel first-then strop.
As has already been pointed out, you can take stropping to different extremes, from 50-80 grit sandpaper that is grinding the metal away, to automotive grit in the thousands, and leather loaded with metal polish.
 
It can, but it doesn't have to. Clean the stones, elevate the angle significantly, reduce the pressure and a few passes should eliminate the burr. Most methods of removing a burr, like cutting wood, or cardboard, or stropping on non-abrasive media tend to actually crack off the burr, often smashing it into the edge which gives far less than optimal sharpness. Just grind it off on the stone for optimal sharpness and strength, in general the only reason to stop is if it gives you access to a grit you don't have with your stones.

-Cliff
 
So tell me if this is right. After sharpening, instead of stropping for a smooth finish, I can move the Sharpmaker stones to 30* to remove the burr? How many swipes should I do on 30*?
 
The sharpmaker has two settings, 15 and 20. If you sharpen at 15, you can deburr at 20, but generally the angle needs to be higher still. It depends on the steel and the heat treatment, sometimes you need a much higher angle than the one at which the blade is honed. Generally, the finer grained and harder the steel, the less the tendancy to burr and the less effort it takes to remove any burr which forms.

-Cliff
 
Well, what do I do if I sharpened my knife at 20*?


Sorry for all the questions, I must seem like an idiot :(
 
You can put something under the end of the base to increase the angle, generally you just freehand it because it doesn't actually make any difference if you knock the burr off at 27, 30 or 33 degrees, and you only make 1-2 passes usually. If this doesn't take the burr off, there are many reasons for the problem and generally the solution isn't to keep grinding at the upper angle. Generally if you are starting off, it is nice to work with simple low alloy very hard steels which form minimal burrs. It would be very frustrating to start to sharpening something like S30V at 57/59 HRC. But on the upside, once you do gain the ability to handle those steels the other ones are trivial in comparison.

-Cliff
 
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