Convex sharpening help please

Make, or buy, a good set of strops, charge them with black, green and white Bark River compound, and never let your knife get dull enough to need sandpaper. :thumbup::thumbup:
 
A lot of people have advised me to stick to using leather strops now, so I think thats the way I will go. I havn't really looked into stropping techniques yet, is it better to have the leather fixed to a hard backing, or to just pull it tight? Do you apply a lot of pressure, or just let the weight of the blade do the work (like when using sandpaper), I don't want to round the edge off.
I know the best way is to practice and experiment on cheaper blades, but I find it hard to find the time at the moment, so this may take some time.
 
You will probably achieve better results with mounted strops. A hanging (unmounted) strop adds another variable to the sharpening equation, tension, which affects the amount of rounding (convexing) of the bevel. It is easy to strop away on a hanging strop and slowly, unconsciously relax the tension applied which will tend to round over the edge. Strops mounted to a firm, flat bases such as glass, have much less tendancy to round the bevel. With either type strop, light even pressure is all that is required. More pressure increases the rounding effect.
 
Ok, thanks for that. All this help is really appriciated. It may be some time though, that I try this out and let you know how I get on.
 
Interesting thread, i usually sharpen with fine grits for my work, and take chisels and plane blades to 6000 or 8000 grit water stone. Knives i do various things with, but noticed when i got my first Dozier that the edge was coarse so i called and talked to Dan and asked what grit they sharpened with, he said 200 then stropped i thought about this and feel that a coarse grit like the 200 makes fine serrations and an edge that is sharp, but has that tearing effect. No one can argue that Bobs knives aren't sharp. I am thinking now of diamond stones with a coarse grit and moving the blade in straight lines to keep the edge like it was belt sanded. Love the way a Dozier cuts. Although my other knives that i sharpened in other ways cut well also, sometimes i think they are too sharp to keep a working edge long if cutting something hard and not dressing animals, but thats where the great steel and heat treat come in.
 
Ok, one more question:
How sharp should it be by the time I have finnished with the sandpaper and am about to use the strop? (e.g. shaving sharp e.t.c)
 
Plinthman said:
Since there arn't many cheap covex blades about, would be ok to practice on an old SAK that I have? I know these dont have a convex edge, but wouldn't the mousepad technique create one? Don't really want to ruin my F1.
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Buy a carbon steel Opinel (convex grind), give it a patina with vinegar, practice the "rocking motion" described by db. Pay attention to where you remove the patina and you will get it.

dantzk.
 
Plinthman,

I am pretty new to this forum but let me share my thoughts with convex sharpening if you would.

I saw a stone mentioned...not by you I don't think...and this is the last thing you want to use. A stone will not follow the contour of the blade and edge like leather will. When you use sandpaper, it is most likely going to be used to profile out a nick in the blade or quickly bring the edge to the point to where you can polish it on a leather hone. Do not use a hanging strop. There is too much give in the strop and the wake of the strop behind the edge will actually dull your edge. "Strop" is a generalized term and what you are actually looking to use is a leather "HONE" to polish the edge and refine it.

As for how sharp an edge should be after sandpaper, that all depends on what grit you use. You can get an edge "shaving" sharp with a fine grit sandpaper...say 1000 or finer, but there is still a bunch of micro serrations that will dull very fast and/or chip out for not having any support from the steel behind them. I personally go all the way to 2500 grit before honing. The edge is nearly complete at this point. You can feel what I say by taking the tip of your fingernail and running it across the edge. If it is not smooth as glass...and I mean VERY smooth like running your nail on glass-no drag, no perceptible vibration etc...it will still need to be honed on a piece of loaded leather to get the edge refined and spooky sharp. Your edge will also last much longer due to all of the support that the blade behind the edge is giving.:thumbup:

This method of sharpening can be used on ANY knife. I use it for my beveled edges and SAK's and convex edged knives.

I have a video on Youtube here... http://www.youtube.com/watch?v=BbOvbht5z_A that will help you out.
 
Ok, I had my first go at convex sharpening. I decided not to experiment on a cheaper knife, but instead follow all the advice here and try to sharpen my Fallkniven F1.
As mentioned before it would slice through paper, but not easily (i.e. if you hold a piece of plain A4 paper at the top, you can slice a peice off the top by drawing the knife back as you slice, but it won't push cut through the paper). So it was still quite sharp, but not as sharp as you would like.

Anyway, I glued a small peice of vinyl flooring to a flat peice of wood and taped some 1500 grit wet & dry paper to that (I couldn't find any leather, and figured this was the same sort of firmness). I stropped on the wet & dry one way, then the next, a total of 500 times. After doing that, the edge seemed no sharper or duller than when I started.

I wasn't really expecting success on my first attempt, but I need advice on where to go now. Do I keep percivering with the 1500 grit, or should I try a courser grit, or do I need to take the knife to a leather strop with compound?

By the way, I wasn't using any more pressure than the weight of the blade, and I held the knife at an angle so that the edge was only just touching the paper (about 15 degrees). I put some permanent marker pen on the blade before I started, and this was removed from the edge, and up to about 2 or 3mm (1/8") away from the edge.

Thanks to everyone for all the help so far, I just need a bit more help getting there.
 
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That's quite a few strokes there, Plinthman. 500? I strop mine about 10 or 15 times, then flip it and do another 10 or 15 on the other side. Then I might go a swipe or three on each side before stropping.

It may be that you weren;t getting the edge, even though you did describe that you were getting it. I'm not enough of a wordsmith to explain exactly how to do it, especially since I can;t see you do it, I certainly can;t say what's to fix.

Keep trying. Experience is an accumulation of success.....and failure. Once you get the edge, you'll understand and be able to repeat it, each time with more accuracy and greater success.
 
Coat the edge with a black Sharpie marker, then make sure you are hitting the edge when sharpening. You can wash off any remnants using nail polish remover.
 
I did put some marker pen on the blade, and it looked like it removed 1/8 inch of it from the edge. Is it possible that Im holding the knife at too much of a flat angle, so the pen is rubbing away from the edge, but there is not enough pressure on the absolute edge? I'm holding the blade at about a 15 degree angle from the wet & dry. Does anybody know if this sounds right for a Falky F1? It looks like the edge is only just touching when I swipe. I'm a bit reluctant to increase the angle until I hear advice from people, because I don't want to round the edge off.
 
Plinthman said:
I did put some marker pen on the blade, and it looked like it removed 1/8 inch of it from the edge. Is it possible that Im holding the knife at too much of a flat angle, so the pen is rubbing away from the edge, but there is not enough pressure on the absolute edge?...
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If the Sharpie ink is abraded away AT THE EDGE then you are working on the edge. You don't need to increase the angle.
 
you can sharpen with any good waterstone that will mud up. waterstones *will* properly sharpen a convex edge, i have much evidence and will produce more the next time I sharpen something. not disparaging anybody's method, whatever works..works.. but to claim that stones do not is an error.

i have done convex edges totally with stones, (to perfection) and totally WITHOUT stones (less enjoyably, for me, and slower).. and I won't tell someone that stones are easy nor that all stones are equal.. but you certainly can use any stone that will produce an abrasive paste during the sharpening session. I generally use a belgian coticule, but for a few knives go to my japanese stones. honestly i don't know the time comparison for results, versus sandpaper or strops, but it'd be different for MY efforts than YOUR efforts, my skill lies with the stones and being vested in that i'll stick with it.. I don't expect others to do it my way lacking my experience.

IF you want to sharpen to a convex edge, just remember stones (very good natural ones, and a few high grade synthetics) ARE an option.. but they'll be waterstones as far as I know.. and the belgians are fastest of the natural stones, due to the garnet abrasive..
 
dantzk8 said:
Buy a carbon steel Opinel (convex grind), give it a patina with vinegar, practice the "rocking motion" described by db. Pay attention to where you remove the patina and you will get it.

dantzk.
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Ok, I've just bought one of those. How do I put a patina on it? Do I just dip it in vinegar? Also I noticed that the blade is very thin and so the angle of the grind is very acute. Should I stick to this angle for practicing or should I put a steeper angle on it, thus creating a sort of secondary convex grind?
 
StretchNM said:
Here's my setup. 7-8oz leather glued to hardwood or MDF. Then, wet/dry taped to the leather. I rarely go below the 1000 grit, most of my sharpening (or, maintaining a sharp edge) is done on the 1500 and 2000.

One side:
convex-01.jpg


The same "strops" flipped over:
convex-02.jpg


I generally strop about 10 times one way, then 10 the other. Then I'll go about 5 and 5. Then back and forth a couple of times, once on each facing of the blade. Then strop with leather and green compound (or lately, the white).

Go to Esav's link for "sharpening the BRKT way". THat's the way I learned. After a time, you'll develop your own technique and feel for it.
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What is MDF?
 
I just sharpen backwards -- pull the blade spine forward/edge trailing across a bench stone. Try it, you'll get the concept. Not fancy, but it works.
 
Esav Benyamin said:
You should practice any new technique on a cheaper knife first.
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I totally agree with this. I use my old beater RAT 1 for this purpose.



As for what grits I have that I use for sharpening convex edges: 220, 360, 600, 1000, 1500, 2000, 3000

I keep all of the above on hand as well as a leather strop.
 
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