Strop Sharpening

K

Kallisti

Joined
Apr 9, 1999
Messages
226
I have found that while sharpening (ATS34 knives in particular), I cannot get a shaving sharp edge without a little stropping. However, when I "over strop" it rounds the edge and blunts it. Should I sharpen knives like a straight razor with the flat of the knife resting on the strop, or try to angle the knife so the edge is perpendicular to the strop? Or just cease and desist and practice more with the (medium/fine) DMT sharpener? Any ideas? Anyone else use strops to finish their sharpening?

Any feedback much apreciated!

Cheers -

Kallisti.
 
After finally getting around to charging a leather strop with white polish,(I've been using a plain leather strop), I'm getting frightengly:eek: sharp blades from what were shaving sharp blades. My best results have been from laying the blade flat or slightly (SLIGHTLY!) raising the flat off the strop. On my convex grinds, the blade is laid flat. On the beveled blades, I'm slightly raising the flats.
Hope it works for you too.
Happy Stropping!:D
 
Is there a stropping FAQ or HOWTO?

I don't think I'm doing it correctly, and I haven't found any good info to set me straight.

Mike
 
You need to get the strop to hone along the edge bevel, the reason that you hold straight razors flat is because this will produce the angle at which the edge is sharpened. On most other knives you will have to hold the knife at a tilt to insure the edge bevel is being hit. Just mark out a couple of sections along the blade and take a pass to check if the angle is right. In regards to rolling, that is usually caused by either too much pressure, or loose form at the end of the stroke which causes the edge to scrape against the strop.

-Cliff
 
Like Cliff said, you want the strop to match your edge bevel. On the other hand, if you are using a strop that is not mounted to a board (a hanging strop) the strop curves significantly as you use it. With a hanging strop lower your angle (lay the blade closer to flat on the strop) to allow for this curve. If you have a convex sharpened blade you will have a lot of the blade surface on the strop.

The above is what I do for minor stropping rather than heavier "sharpening" on the blade. I you press hard on a hanging strop it will tend to wrap around the edge and can dull it. Apply more tension on the strop to make it straighter and use a lighter stroke if you are using an abrasive compound on the edge. Better yet, use a harder leather strop and lay it on a counter or use a harder leather strop mounted to a board when you are "sharpening" your blade.

Having said that, I have given up sharpening with a strop (I only lightly work the edge after I sharpen). I use a diamond hone, then ceramic rods, a smooth steel, and only lightly strop at the end. The harder steels don't work for me if I strop too much. It seems to dull the edge.
 
I no longer like stropping, it just dulls the blade. I have stropped a spyderco delica and a sebenza using strict form and they both come out duller than after i finished on the flat sides of the white stones on the 204.
 
I happen to find Stropping to work well for me, I can bring a slightly dull blade back to sharp sometimes using just that. I sharpen my knives on several things, depends on the mood and on how bad the edge has gotten, I sharpen a lot of knives for guys at work and they don't bring them around as often as they should!

I have a nice large Norton oil stone setup to help put the initial bevels back onto a blade, then I have all three of the Spyderco Flat stones, as well as a Double Stuff and the Profiles.

The strop I have is one of my own making, glued leather to a FLAT board and rubbed in green buffing compound, though some will tell you that you needn't bother with the compound but I find it works very well.

One of the ~Tricks~? is to make sure that when you strop, that on the return stroke BEFORE you flip the knife over, RAISE the blade OFF the strop, this will help prevent you from ROLLING the edge and possibly ruining all the work you have completed. So imagine if you will, pulling the knife away from you, stropping along the strop and when you reach the end of the strop, lift the blade up, THEN rotate the knife so the edge is facing away from you, set it back down and pull towards you, again when you reach the end RAISE the blade UP off the strop BEFORE you rotate the knife...just becareful!

G2
 
Glad it works for you Gary. I only wish it worked for me. I do as you said and lift the knife off, as well as wiping the edge with my shirt after sharpening to take most of the microscopic grit off. It just does not work for me, and I have tried both smooth and textured leather.
 
Originally posted by CarlRexHubbard
....as well as wiping the edge with my shirt after sharpening to take most of the microscopic grit off....
Click to expand...

Good point, I lay a piece of paper towel on top of the strop and then strop the knife on top of that to remove any fine grit from the edge as well as any buffing compound.

Carl, what is your leather placed on?
G2
 
Gary W. Graley wrote :
The strop I have is one of my own making, glued leather to a FLAT board and rubbed in green buffing compound, though some will tell you that you needn't bother with the compound but I find it works very well.
Click to expand...

This is essentially the same set-up I have. Only difference being I use a fine white buffing compound. With a little patience and practice this system can take a shaving sharp blade to a stunningly sharp blade in just a minute or two of stropping.
Guys, it pains me to hear your having problems with this.:(
When done right it really makes a difference.

Cliff Stamp,
As usual, you are spot on with your assessment.:)
 
I just made a strop a few days ago myself. I glued leather onto a board and rubbed in green buffing compound as well. The edge I have is definitely the sharpest polished edge I have produced. Lifting the blade off liek Gary said is important. I also use a "medium" pressure, then after some strokes I lighten up on the pressure more and more.

Michael, give it a go on a paring knife from the kitchen. Sharpen a paring knife and slice some paper. then strop the paring knife, and slice the paper again to feel for any difference.
 
Carl :

I have tried both smooth and textured leather.
Click to expand...

Unless you are using a polishing compound on the leather stropping will do very little on modern cutlery steels. I usually finish on plain leather, after working on a CrO loaded strop, however the change the plain leather produces is very small, 10-15% reduction in force to push cut light thread, so you have to be doing some very careful cutting to appreciate it.

However stropping by using a loaded piece of leather is the same as using a fine hone, with the small difference that leather gives a little and thus will produce a light convex edge. The difference that this honing can make can be dramatic depending on the state of the edge. To get specific take a look at the NIB sharpness section of the following :

http://www.physics.mun.ca/~sstamp/knives/TAC_11.html

You will see that a simple stropping makes a very significant improvement to the edge. It can be used to keep an edge sharp, or as a finishing step. Even the finest stone (8000 grit Japanese waterstone), is about twice as rough as the finest buffing compound (CrO - 0.5 micron).


Jeff :

The harder steels don't work for me if I strop too much. It seems to dull the edge.
Click to expand...

All steels should benefit from a stropping after a fresh sharpening. However after some dulling, some steels respond much better than others. The hardness is not the problem as the hardest steel is soft compared to buffing abrasives, however there is a problem with high alloy carbide steels. They tend to resist stropping after they have been dulled because the edge is now highly carbided (the steel will wear away first) and the majority of the alloy carbides are far harder than the abrasives in the polishing compound so instead of being recut, they are just further rounded out. Simple steels like 52100 can continue to be stropped for quite some time, but complex ones tend to need a higher quality abrasive after they have been dulled. SiC will do and you can get it in fine grits from Hand American and Lee Valley. Diamond dusted sandpaper will do as well.

-Cliff
 
I went to the salvation army and bought a leather belt for two bucks. It seemed pretty dense and firm, it was just natural leather. I then went and got some green buffing compound, the finest Lowe's had, and loaded up the textured side. Nailed it down to a piece of wood. Did not work well, so i flipped the leather over to the smooth side and loaded it up. That did not work well either. I am following all the techniques you all are describing. The only thing i can think of is that the leather sticks out over the edge of the wood about an 1/8 of an inch on both sides(width of the strop), which might round off the edge. Good thread by the way.
 
Great information guys. I have some stropping compound but haven't been using it. I have been mainly using the canvas side which has been well used as it came from a barber's shop. I'll try loading it up. Sounds like I was using too much pressure on an insufficiently taut strop. Thanks for all the excellent imput. Back to the strop I go...
:cool:
An alternative to lifting the blade off the strop at the end of the stroke is to rotate it around the blade spine I guess, like razor sharpening.

Stay sharp


Kallisti.
 
Carl. I have often used belts with great success. I would guess that your knife was too dull to benefit from the very fine abrasive of the polishing compound.

Cliff. I don't find extensive stropping very beneficial on freshly sharpened high alloy blades. When I do extensive stropping it is part of my experiments to see what is the sharpest edge that I can achieve on a particular blade. Yes the stropping helps initially, but beyond a maybe a dozen light strokes per side it seems to dull the edge. I don't think this is simply the polishing of the edge reducing slicing efficiency. I haven't given up on the concept, but I haven't made it work for me yet. I have several strops to work with and I guess I'll try some alternate abrasives. What I've mostly been using is green chromium oxide compound. I have tried stropping on 1500 grit SiC paper with unimpressive results. I'll have to go shopping for something else (what fun).
 
I have never seen stropping on CrO, or plain leather have a negative effect on push cutting ability (light thread), but it can destroy slicing ability (1/4" poly) quite quickly, the extent of which depends strongly on the steel being stropped.

However the matter is a bit more complicated as slicing ablity is strongly dependent on what load is being applied, low load performance (<500 g) will show a rapid degredation with stropping, whereas under loads approaching 1000 g the slicing performance will actually increase because the polish approaches the rupture point of the thread and it becomes a push cut.

To make matters even more complicated, the angle of the edge also influces the performance as what you are actually looking at is cutting ability of which sharpness is only one factor. A more acute edge angle can cause the rupture point to be lower than 1000 g or much more, so the above are only rough guidelines, for an edge of about 15-20 degrees say.

The matter has been studied in significant detail by Lee who concluded the finest edge (in regards to push cutting), was formed by a 8000 grit waterstone following by polishing with CrO. He was able to achieve edges of quality greater than razor blades on various chisels. You can clearly see in his book on sharpening the difference that the CrO compound makes to the edge.


-Cliff
 
Originally posted by Cliff Stamp
...The matter has been studied in significant detail by Lee who concluded the finest edge (in regards to push cutting), was formed by a 8000 grit waterstone following by polishing with CrO. He was able to achieve edges of quality greater than razor blades on various chisels. You can clearly see in his book on sharpening the difference that the CrO compound makes to the edge.-Cliff
Click to expand...

Cliff, what book is this you are referring to? Interested in adding to my library!

G2
 
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