Stropping k390/15v, drawing out a burr?

E

elevator man

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Oct 14, 2023
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I'm looking for some input on what yall do for stropping.

I have two strops, one is balsa with .5 micron diamond spray, the other is balsa with 3 micron diamond paste.

I've had great results initially stropping k390. I sharpen with diamonds, then deburr very carefully, then strop. What I'd done was a few passes on the 3 micron then more passes on the .5 micron. This first edge was amazing, I'm confident there was no burr. I cut through thick plastic banding on crating, cut boxes, many zip ties. Treated that thing like it owed me money and the edge was still good after two weeks. No reflection off the edge and was still shaving a little bit with more force. Sliced paper great.

I decided to strop it again to keep up the edge, and stropped a good bit on the 3 micron then a good bit on the .5 micron. Matched bevel well, very light pressure. The edge was razor sharp now, mirror polished. Next day at work cut through some thick felt. Then a little later went to use it again and noticed it looked like I'd bashed it into concrete. The whole edge was reflecting light. I knew there's no way after what I'd put this thing through the last 2 weeks that the steel should look like that after a piece of felt.

The only explanation that makes any sense to me is the second time I stropped it, I went overboard and drew out a burr, which then folded the next use.

I'm just wondering what yall do? I get that stropping only improves the edge that's there and can't bring back no edge. But I'm kind of shocked to have actually made a burr by stropping. How many passes do yall do before being done? Should I just skip the 3 and only do a few passes on the .5 micron when maintaining? What measure of sharpness do yall wait to see before stropping to maintain an edge, as soon as it stops shaving?
 
In my personal experience if I strop and I am not consistent with my angles, I can mess up a sharp blade. When I am stoping to touch up a blade, I just do a few light slow edge trailing strokes, following the bevel. If I speed up, I mess up. I have just started using diamond, and it can cut a lot more steel than my green compound. I am sure I am going to get some others contradicting me, but I think that the green compound still is able to help keep the powdered steels tuned up between sharpening. Although I am still experimenting with diamond., I just ordered more diamond spray and balsa strops from Gritomatic and see if that changes anything.
 
I think you can definitely create a burr from stropping, particularly using an abrasive like diamond and also if you "stropped a good bit".

The only thing I would advise is that if you feel the need to do anything more than a few strokes on a strop to bring back an edge, then IMO you would be better off getting your finishing stone and doing a few light edge leading strokes on it as if you were deburring then maybe 3 or 4 strokes on a strop if you think you need it. I think it would work better and be quicker as well.

On the other hand, the felt may have had some grit or something in it that caused the dulling. Some materials are surprisingly hard on a knife edge, even high wear resistant steels.
 
Just to add, the STROPPY Stuff utube Chanel had a good video on stropping for beginners that I just watched.
You may want to check that out. I do not believe I can link to it as he is not a Blade Forum sponsor/member.
 
I believe felt is an extremely abrasive material, so cutting it could well dull your blade. Folks use felt wheels and belts to strop knives. Some people will do one or two passes through a rock-hard felt cube to remove burr.
 
I have strops with all sorts of different diamond compounds and a week ago I borrowed from work Meusburger highly concentrated 6 micron diamond paste to load one of my strops.
I wanted to try it how it works. You won't believe but this compound just doesn't cut. It just drags the burr arround and does not cut it off.
This is not directly related to your problem but I thought it would be good to know.
 
Stropping with very fine compounds is an extension of sharpening, in the sense it can continue to thin the edge to the extent it's no longer strong enough to be durable. So it folds in use, like a burr will do. Effectively the edge is burred when it gets too thin. We usually think of the 'burr 'as being when the too-thin edge folds to one side or the other - then it's obvious. But until it folds over, it can mimic an extremely refined & sharp edge in very light cutting tasks, like shaving hair or slicing fine paper. But something like felt is very tough on edges that aren't strong.
 
So I had a chance today to cut the same felt after I freshly sharpened the same knife last night. Sharpened almost exclusively edge leading. Trying my best to not build up a big burr to start. After coarse I sliced wood a couple times. Then same edge leading only strokes one fine then extra fine. Then 2 passes on 3 micron diamond strop then 4 or 5 passes on .5 micron diamond strop.

Cut the same felt way more than I did last time. Solid 10 cuts. This time the edge shows no wear or anything at all, still blowing air off my arm. So I think I must have drawn out a burr the last time. I'm going to have to work hard at deburring then not making one by excessive stropping
 
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