Sharpening a convex blade/ sandpaper+mousepad

SpookyPistolero

SpookyPistolero

Joined
Dec 13, 2005
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Howdy folks,

I recently got a new bushcraft blade which I was hoping to make my 'go-to' knife. Unfortunately, I just cannot get the thing sharp. It's a convex and probably the first one I've ever had. I've read a lot about sharpening this type of edge and have been working at using a mousepad with various grits of sandpaper on top. I started with 600, then worked down to 320 when that didn't work. Tonight, I finally tried 100 grit in an act of desperation. No luck! I just can't make this blade cut.

It's a pretty thick blade:
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..but I don't feel like it's so thick that it wouldn't be able to sharpen up decently. (The blade for comparison is a Mora 510.)

I feel like I'm doing things as per various instructions as far as the stropping technique on the sandpaper and understand the principle well enough. I have no idea what the steel type of the blade is, which may be playing a factor.

Anyone have any tips of experiences trying to make a convex actually cut something?

I'm really learning to appreciate my Moras a lot more-a after all this. Those scandi blades will sharpen up in a jiffy.

Thanks for any thoughts or advice...

-Spooky
 
on a mousepad you may actually be rounding the edge over becuase it is soft and it could be giving too much.

i use sandpaper on top of thin corrugated cardboard, and i have had great results.

also, are you laying the knife flat on the mousepad or are you tilting it up like you would do with a stone? if you are tilting it up you are almost deffinately rounding the edge
 
I've been laying it with a slight angle, but much less than I would have used on a stone. Should I be laying it flat? I'm not even sure that I will be hitting the edge if I lay it flat actually. I will probably give that a try next. I will also try laying it on some thin cardboard to see if that helps.

Thanks-
 
I don't know if it helps (i'm not a great sharpener) I recently got a fallkniven f-1 also a convex grind (the factory edge is plenty sharp for me, so I haven't sharpened it yet) The literature that came with the knife reccommended sharpening by pasing the knife over a stone as if you were (Theoretically) cut thin slices from it (sandpaper should work as well) decreasing pressure as you work...Granted these are simple instuctions but if the mousepad method is not working it might be worth a try...let me know how it works out. Good luck!
 
SpookyPistolero said:
I've been laying it with a slight angle, but much less than I would have used on a stone. Should I be laying it flat?
Click to expand...

On a mousepad lay flat the blade and follow the curvature giving a slight angle until the edge meets the sandpaper. On a stone it's the same but as you begin by the edge you give a slight angle, follow the curvature by twisting your wrist until the blade goes flat to the stone. No pressure, go slow and light. A bit of practice and you will state it's really easy.

dantzk.
 
I think Siguy may be right. Some mouse pads are very soft and you may have rounded the edge over while raising the spine and putting pressure down on it. 100 grit can round off the edge pretty quickly.

I would suggest using a regular stone and flattening out the primary bevel down until you get very close to the edge. From there you can use your 100 grit sand paper on top of a harder surface such as leather or cardboard. With the sand paper just follow the primary bevel and then slightly raise the spine towards the end of the stroke. Gradually move up to higher grits until you are satisfied with the polished edge. Just make sure the the edge is formed properly during the lower grits before moving up.

Ban
 
I've had good results sharpening an S1 by folding an old rag in half, with crocus abrasive cloth laid on top. Takes a couple minutes with moderate pressure on a solid surface.
 
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You're probably using way too much pressure. When using a mousepad you need to use very light pressure, no more than the weight of the knife itself. When you're at the point where you're thinking, "This couldn't possibly be doing any good", you're about right.

I would recommend using a firm leather pad instead of the mousepad. I find it works better.

Finally, check this for a bit of help: Convex Guide
 
I second Grampa and siguy. I'm getting good results with two standard pieces of corrugated glued together, for a somewhat stiffer backing. The link Grampa posted is a great one :thumbup:
 
Part of your problem is that is a lousy blade grind. It is a very narrow saber grind which gives you a rather obtuse honing angle. You need to sharpen rather flat on that surface to get reasonable cutting performance. When you sharpen that close to the primary grind angle you have to remove a lot of material (a lot of work). I would use a belt sander and convert it to a flat scandinavian grind like the Mora (as a minimum). Actually I would lean on the belt sander and widen that bevel by at least an eigth of an inch.

Experiment with cutting some cardboard. No matter what edge you put on that thing it will really drag in the cut.

If you don't have the patience to do heavy rework on the blade, just sharpen it with a file. The rough edge finish that a file leaves is perfect for obtuse blades like this.
 
as i understand it it is lacking sharpness.

i notice that it looks like a scandi grind with the shoulders rounded a little bit.
it would probably work out okay, except that the steel looks to be about three times thicker than the mora, and therefore the edge will be very thick.

i would also suggest taking the shoulders of the grind back, either with power tools or alot of work on a stone or with rough grit sandpaper on a flat, hard surface (glass, 2x4 etc) that will improve your cutting ability and possibly help out with actual sharpness
 
If it is sharpness, you are probably just not hitting the very edge. It takes a lot of work with such a wide bevel to grind it back when it is not very sharp.

-Cliff
 
Thanks much for the replies thus far. It is correct that it is lacking cutting ability. It just isn't sharp at all.

I've been playing with different grits on harder surfaces (on top of a thin carboard folder over a book, etc.) but haven't had too much luck, though it is still a bit sharper than it was with the mousepad.

I was worried that folks would suggest removing material from the shoulder area, I was hoping to get away from that. I don't have access to a belt sander now so lots of hand work with low grit paper will be in order I suppose. I'm contemplating finding someone to send the blade to for re-grinding.

I'm going to keep trying at it and see how things start looking. Not being able to get a knife sharp is like not being able to get your rifle zeroed. What a pain!!!
 
Forget about mousepads, the primary grind is likely hollow and the edge burned so it will take some time to flatten the grind and get to quality steel. I would suggest a slight micro-bevel to get the knife working immediately and then as time allows just flatten the primary with an x-coarse hone.

-Cliff
 
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