Am I stropping wrong?

Kershaws

Kershaws

Joined
Aug 3, 2013
Messages
592
So I have a tendency to make tiny tiny nicks on my arm once in a while after sharpening a knife to test out the slicing ability, recently I put a lot of work on this one folder (AUS 8) to get a good 20 degree mirror polish edge, I ended it with a leather strop with green compound, stropped it for around 20 minutes, then wiped the blade edge with Alcohol and a cloth, when I tried to nick my arm it would not cut the skin even after moving the blade up and down across the surface, now if I tried with some more pressure im pretty sure it would, but I would be an idiot to try that. Next I got a regular piece of computer paper and tried to slice it, the edge sliced the paper the same if not worse than some of my other coarse (1000 grit) folders, have I rolled or rounded off the edge?
 
It sounds like you're spending too much time with stropping and could be rounding the edge.
 
It's possible you're using too much pressure when stropping which will dull your edge. Try stropping only using the weight of the blade.
 
+1 for both. Depending on my steel, I only strop for a minute or less stopping often to check progress. It sounds like you are undoing your perfect edge.
 
I guess I just figured it out then, when I strop I put a couple of pounds of pressure on it, i'll see if using the blade weight will work. thanks!
 
I don't strop at all. I do most of my honing on a fine/ultra fine Eze Lap diafold. After the ultra fine, I find no need to strop. Not after a polished edge anyhow, I like the toothy edge a diamond hone gives my knives.
 
Tiny nicks out of your arm?:eek: Whatever works for you...

Good luck getting that edge the way you want. It's pretty frustrating spending all that time sharpening to end up with a dull knife. I've been there. It may be helpful to take a break altogether or work on a different knife for a bit. Sometimes when you leave and come back it just clicks.
 
Kershaws said:
I guess I just figured it out then, when I strop I put a couple of pounds of pressure on it, i'll see if using the blade weight will work. thanks!
Click to expand...

Yeah, no pressure at all when stropping.

On bigger blades you may even need to support the knife.


If your strops leather is too soft or thick, it could be part of the problem.




Big Mike
 
20 minutes' stropping on AUS-8 with green compound is likely overdoing it. The edge is probably over-polished and, if it wasn't quite fully-apexed prior to stropping, then it further exacerbates the problem. A less-than-completely apexed edge with some coarse 'teeth' from the stones will dull very quickly when the teeth get polished away, leaving a very round or blunt edge behind. If the edge is fully apexed off the stones, it should already be taking at least a few hairs from the skin, and biting into it as well, after which no more than 5 minutes of stropping (maybe much less, down to 10 passes or less) on green compound should clean it up and have it really popping hairs.

Relating to pressure:
Wider bevels + firmer stropping substrate are more tolerant and forgiving to greater stropping pressure, assuming technique is good (controlling the angle). The wider bevel is better able to distribute pressure, and the firmer substrate (like wood, for example) won't compress/deform as much under the pressure.

A big, heavy blade with relatively narrow bevels (wider/more obtuse edge angle), and a softish strop are a troublesome combination, in trying to prevent rounding of the edge. Even the weight of the blade by itself may exert too much pressure on the narrow bevel, causing it to sink into a soft substrate and round over the edge. Conversely, any blade with very wide bevels (very acute edge angle) is a cinch to strop on a firm surface like wood, or paper-over-glass. A very light and acutely-ground blade can be laid nearly flat against any stropping surface, hard or soft, and it's much easier to regulate pressure on the apex to feather-light levels, and minimize edge-rounding. This is why it's often easy to put that final 'pop' in an edge by stropping on the otherwise softish-backed thigh of your jeans, while you're wearing them, just by 'brushing' the side of the blade against them.


David
 
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I think I've identified at least 3 different levels of stropping. Each level serves a different purpose. This list below refers to stropping on leather or some other surface with similar give. I usually use white or green compound, which seems to greatly accelerate the effect. Stropping on bare cardboard or leather doesn't seem to work very fast. With that in mind...

1. Doing 3 - 10 strokes per side. For me, this seems to remove the last little "hangs" of burr being left behind. It takes an edge from catching paper and ripping it, to clean slicing. This can be from a rather coarse stone. Same story with shaving hair: Before stropping it will catch and only shave a few hairs. After a mere 3 to 10 strokes per side it shaves much more cleanly. I guess this is like cleaning up the edge.
2. Somewhere above 10 strokes, perhaps 20 to 50 seems to be this intermediate state where the edge gets more smooth, and mostly in a bad way. At this level the shaving performance increases. The "slick" feel through paper gets better. But the ability of the edge to catch the material it's cutting is vastly reduced. I was quite surprised by this with some recent kitchen knives. Tomato slicing ability seemed quite reduced when stropped at this level. Again, shaving and paper were noticeably better.
3. At some point, perhaps after the edge has been refined with very fine abrasives (greater than fine ceramic or EF DMT), with a lot of stropping, the edge gets an extra level of polish. This is alien territory to me, as I don't have any experience with abrasives fine enough to use stropping as an additional level of polish. People talk about it here all the time.... going from some fine abrasive to compound on a strop and getting "more of a mirror polish", or just "more polish". This is either a placebo effect, or it requires very, very fine abrasives before stropping. Either way, I have yet to experience this, but have read about it many times.

I'm still learning here, so perhaps my observations aren't 100% correct. I'd be happy to read others opinions and experiences on this.

Thanks,

Brian.
 
Have you ever seen a barber stropping for 20 minutes?
Stropping is the finishing step in sharpening, and should only require 10-20 strokes per side, not 20 minutes.
 
bgentry said:
I think I've identified at least 3 different levels of stropping. Each level serves a different purpose. This list below refers to stropping on leather or some other surface with similar give. I usually use white or green compound, which seems to greatly accelerate the effect. Stropping on bare cardboard or leather doesn't seem to work very fast. With that in mind...

1. Doing 3 - 10 strokes per side. For me, this seems to remove the last little "hangs" of burr being left behind. It takes an edge from catching paper and ripping it, to clean slicing. This can be from a rather coarse stone. Same story with shaving hair: Before stropping it will catch and only shave a few hairs. After a mere 3 to 10 strokes per side it shaves much more cleanly. I guess this is like cleaning up the edge.
2. Somewhere above 10 strokes, perhaps 20 to 50 seems to be this intermediate state where the edge gets more smooth, and mostly in a bad way. At this level the shaving performance increases. The "slick" feel through paper gets better. But the ability of the edge to catch the material it's cutting is vastly reduced. I was quite surprised by this with some recent kitchen knives. Tomato slicing ability seemed quite reduced when stropped at this level. Again, shaving and paper were noticeably better.
3. At some point, perhaps after the edge has been refined with very fine abrasives (greater than fine ceramic or EF DMT), with a lot of stropping, the edge gets an extra level of polish. This is alien territory to me, as I don't have any experience with abrasives fine enough to use stropping as an additional level of polish. People talk about it here all the time.... going from some fine abrasive to compound on a strop and getting "more of a mirror polish", or just "more polish". This is either a placebo effect, or it requires very, very fine abrasives before stropping. Either way, I have yet to experience this, but have read about it many times. Long term maintenance with a leather strop is best dome on convex, Scandi, and straight razors - tools that have a lot of additional contact with the strop beyond just a thin cutting bevel. On regular V bevel there is very little room for error in pressure or angle control before negative effects start showing up.

I'm still learning here, so perhaps my observations aren't 100% correct. I'd be happy to read others opinions and experiences on this.

Thanks,

Brian.
Click to expand...

Brian, so much depends on how you apply the abrasive to the edge. Put your compound on MDF, or wrap a sheet of paper around your stone and the effect will be very different from leather, even fairly hard leather. Then rub compound on a piece of hardwood with a few drops of mineral oil to make a thick slurry, the effect will be different again. There is a ton of contributing factors. If using leather to strop, you must use either a larger grit abrasive or use far fewer passes to maintain a lot of bite. Rounding of two or three degrees per side will noticeably increase your inclusive cutting angle, and this amount of rounding is easy to hit with multiple passes on leather, especially with a V bevel where sinking into the surface or variations in angle control will have a larger effect. That's why less is more when stropping on leather - have to do more stone work with only a very few passes to finish for best control. Long term maintenance with just a leather strop is best done on convex, Scandi, and straight razors - tools that have a lot of surface contact with the strop outside of a narrow cutting bevel. Even then, many convex and Scandi aficionados prefer to use a black and white compound on two strops to get best results. Can be done with a V bevel but will be unforgiving of too much pressure or loss of angle, and even then over time it will require trips back to a stone to restore a crisp apex.

I took some micrographs of edges at various stages that might illustrate to some extent how the cutting edge interacts with different materials.

http://www.bladeforums.com/forums/showthread.php/1095175-Help-with-edge-aggression!

There's a lot to it, go slow.

Martin
 
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Kershaws said:
then wiped the blade edge with Alcohol and a cloth, when I tried to nick my arm it would not cut the skin even after moving the blade up and down across the surface, now if I tried with some more pressure im pretty sure it would, but I would be an idiot to try that.
Click to expand...

What part of this is not being a idiot?
 
Also, find a better sharpness test, if you end up honing an edge better than you thought, or if you stop at a coarser grit, you're gonna end up in the doctors office
 
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