Stropping

[thebladeguy]

HI um may someone tell me what it means to strop? I kinda know but I am not totally sure. Also what do you use to strop? Thanx,

TBG...................

 

[yuzuha]

It is basically wearing off the burr by polishing the back of the bevel on a strip of leather by pulling the knife along with the edge trailing behind. You can charge the strop with a stropping compound. Leather is flexible so even with light pressure (weight of the blade generally), the high part of the bevel will push down into the leather, which will then spring back to normal after the blade passes (and, in doing so, will just barely clip the edge as it passes). This page shows the basic technique though I use stuff that is closer to 30,000 grit rather than 600 grit (you could do this if you don't have anything but a 100 grit cryslotron stone, but that is way too coarse IMHO) http://www.capeforge.com/contstrp/

For stropping things go here http://www.handamerican.com/products.html#Leather Flatbed Hones

 

[Cliff Stamp]

Stropping just means the edge is hauled backwards over the sharpening media in contrast to normal honing which pushes it into the abrasive. You can strop on anything, usually done on leather, sandaper and cardboard/paper.

-Cliff

 

[STR]

This site is a good warmer upper to stropping convex edge knives but stropping works well for any knives to 'set the edge' so to speak. Once a knife is sharp stropping is the best way to maintain that edge. Frequent light sharpening is much easier to do than infrequent radical sharpening so it is well worth the time to get to know stropping techniques and start doing it with your own cutlery.

http://home.nycap.rr.com/sosak/convex.htm

 

[TedGamble]

Yuzuha, Thanks for the CapeForge link. It's a great one.

 

[knifetester]

Once a knife is sharp stropping is the best way to maintain that edge.

Sometimes a quick stroping can be used to bring back a slightly dull edge. However, if you are doing some serious cutting you will need to sharpen the edge (reset at least the micro-bevel).

As well, continued stropping (on leather) to sharpen the edge is not not always optimal, as you want to shed any weakened metal and cut new faces on the carbides. This means using abbrasives, eitha stone for a v-grind or sandpaper for a convex.

Just my opinion. . . .

BTW, Buzzbait's page is excellent. For some really good advise on stropping and convex edges see many posts made by Thom Brogan.

 

[STR]

Using abrasives on a highly polished edge is just going to dull the edge down from where it was with peaks and valleys. (see pic) It may appear sharp to the finger or even when slicing at first because it will have a bite but that edge will not last as long as a uniform highly polished edge.

When the edge bevel is no longer steep enough to make a slice or do what you want it to do or when the edge becomes so rounded from stropping it numerous times it is then time to reprofile with an abrasive and re flatten the bevel but once that is done stropping maintains it for you until the next reprofile.

 

[mthall47]

It is basically wearing off the burr by polishing the back of the bevel on a strip of leather by pulling the knife along with the edge trailing behind. You can charge the strop with a stropping compound. Leather is flexible so even with light pressure (weight of the blade generally), the high part of the bevel will push down into the leather, which will then spring back to normal after the blade passes (and, in doing so, will just barely clip the edge as it passes). This page shows the basic technique though I use stuff that is closer to 30,000 grit rather than 600 grit (you could do this if you don't have anything but a 100 grit cryslotron stone, but that is way too coarse IMHO) http://www.capeforge.com/contstrp/

For stropping things go here http://www.handamerican.com/products.html#Leather Flatbed Hones

I appreciate the links. I was just about to ask if stropping would help as a final step after using my ceramic rods + ask where to get strops, etc.

 

[Cliff Stamp]

It may appear sharp to the finger or even when slicing at first because it will have a bite but that edge will not last as long as a uniform highly polished edge.

The opposite is true if you slice with the knife, not only is it sharper, but the edge actually lasts longer with a more coarse finish.Not every tool is designed for push cutting.

It also depends on how the knife dulls, you would not want to keep stropping a large chopping knife because it works well on a small carving tool as they blunt in different ways.

The small carving tool will blunt by deformation and wear and the large chopping tool by fracture, leave weakened steel on its edge and you raise chance of significant failure.

Some steels as well don't respond well to stropping as it is prone to burr formation and need aggressive edge into honing to produce a clean edge. These are steels with a combination of lower hardness and high wear resistance usually.

Stropping as well doesn't mean high polish, you can strop on a 220 grit SiC hone, or a 80 grit AO belt and produce a very rough finish.

-Cliff

 

[STR]

The opposite is true if you slice with the knife, not only is it sharper, but the edge actually lasts longer with a more coarse finish.Not every tool is designed for push cutting.

I completely disagree with this statement. Not only does it go against everything in my experience but it goes against everything I have read or have in writing at my disposal regarding an edge and the maintainance of an edge. A course edge cuts. No diagreement there but it is certainly not as sharp as the blade can be if it is course. A course edge is harder to make push cut so I agree there.

A highly polished edge can be attained where you can slice well and push cut well also. It is an individual taste thing as to the final edge or the medium used to get there though. Outside of 'big choppers' I would suggest a medium or fine edge on your pocket folder. For general use they stay sharp longer that way.

Also, stropping most always removed the burr in my experience. It didn't create them. Maybe you are speaking of stropping on a grit stone or paper there?? For me the easiest way to remove a wire edge has always been on a leather strop.

 

[Cliff Stamp]

... it is certainly not as sharp as the blade can be if it is course.

It is sharper when slicing, meaning the required force (or length of edge under a given force applied) necessary to make a cut is reduced.

A highly polished edge can be attained where you can slice well and push cut well also.

Yes, and then you can lower the grit and move the performance more towards slicing at the expense of push cutting performance.

To say that a course edge is sharper and will last longer is just not true.

Yes which is why I didn't say that. I said during slicing it will last longer and be sharper. It isn't true for all cutting, what you gain in slicing you lose in push cutting.

As for where it comes from, I have done it, based on work I first read by Mike Swaim who mainly used files on softer steels and Joe who extended it and used rougher hones.

Several of the reviews contain comparison of edges at different finishes showing the dramatic difference it can make both in regards to initial sharpness and edge retention, some of them even note the gains in slicing and the loss in push cutting.

Phil Wilson has done similar work, many of the methods I used are based off of the way he does the cutting as he is one of the few who quantified sharpness and actually measured the force required to cut the rope.

Phil prefers a rough SiC finish on his knives, some other makers prefer diamond, and some prefer a sightly finer edge on an india stone. These are all massively rough compared to a true polish like 8000 waterstone + CrO.

Joe discusses this in the FAQ.

-Cliff

 

[STR]

not only is it sharper, but the edge actually lasts longer with a more coarse finish.

That isn't what you said? I didn't see slicing in the sentence with it. If that is what you meant I follow now.

Also, I tried to edit out some of that but you beat me to it. I think we are on the same page regarding the rest.

 

[Cliff Stamp]

You cut out the qualification which precluded it :

"The opposite is true if you slice with the knife, not only is it sharper, but the edge actually lasts longer with a more coarse finish."

When knife is used on a draw, you can increase the sharpness and edge retention by lowering the grit.

There is a poiint at which performance starts to suffer, I have tried 100 AO it works well, 80 grit works well for others, 40 grit ZO I found useless.

This was mainly testing on hemp rope, which is what Phil uses for stock testing as well as he found it correlates well for his hunting and fillet knives.

Mike Swaim did a lot of cardboard cutting, but actually worked processing fish which is where he gathered most of his data.

Joe had one of the landmark posts on this issue with "How to make a Benchmade Axis perform."

http://www.bladeforums.com/features/makeaxisperform.shtml

Which also discussed the influence of the edge angle, when you combine the two modifications at the same time the result is insanely high.

The edge retention issue I looked at in great detail in the early reviews (fine vs coarse), this was also discussed a great deal on rec.knives.

A landmark post in this area was in 98 when Mike first proposed the arguement for greater edge retention with *lower* edge angles.

Like a lot of what he did and said, it was pretty revolutionary for its time and flew in the face of "those in the know".

A lot of what I had done and work with regarding knives came about from thinking about the arguement he presented for that viewpoint.

He makes a clear distinction between extent of blunting and lifetime of the cutting ability.

-Cliff