convexing w/out a belt sander is not fun!

BryFry

BryFry

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Ok, so I'm pretty good at free hand sharpening with flat stones, but I'm pretty new to convex edges. Since joining this forum I've read all the theory behind it. I've watched the videos. I bought a dozen grits of sandpaper, 120-2000. plus leather strop. -I do not have a belt sander, (for the record)

Wanting to learn how to reform a standard V-edge into a convexed one I dove in, practicing on various inexpensive blades, and got equally varried results. I started to think I was getting the hang of it, so I worked up the courage to try this method out on my favorite EDC blade, my Bradley Mayhem S30V straight edge bali.

I got this knife about a year ago, and have been using DMT diamond stones on it with decent results. But I wanted it to have that spectacularly sharp, beautifully high pollished edge that we all love. Here's how it went...

Started by knocking off the shoulder with my DMT stone, then 180 grit on leather backing, (I find mouse pad to be a bit too soft) ...this is where it gets frusterating...

I can see the new edges forming, but it is soooo incredibly slow going, from every thing I've been told it is very bad to use much pressure with this method, so not wanting to mess up my favorite pocket knife, I took it slow with light pressure switching often to fresh sheets, and....

I kid you not, I DID THIS FOR OVER 25 HOURS, over the course of three days and the edges HAD STILL NOT COME TOGETHER AT THE EDGE!!! :barf: But it looked to be getting close so I switched to 220 and worked that for several more hours...

Are you supposed to be able to form a burr with this method?? Because I've never been able to!

Eventually I brought the angles of the edges together, and moved through the rest of the grits to 2000, then stropped with black then green compound on leather.

After 5 days and 35+ hours of hard careful work, I ended up with a blade that looks OK, but is slightly LESS SHARP THAN WHEN I STARTED!!!! :grumpy: ARRRRG!!!

Part of me wants to start over, and part of me wants to throw all my sandpaper in the trash... :o

I need help...! Is there anyone that reforms there edges with just sandpaper?? What am I doing wrong??
 
Well I can tell you this, if the edge was already semi shallow, it should have taken you ten minutes to get a burr, and then switch it over to the other side. This is the way I see it. You must be pressing WAY to lightly. It is ok to put some pressure behind it. Just don't push as hard as you would on a low grit stone. When I do mine, i press down a decent amount. About as hard as I press on a 1000 grit stone. Not hard, but not with just the weight of the blade either. I'd say try again, press hard enough to get a burr. It is when you are progressing through the grits and get higher up that you use less and less pressure. Its the same with stones.
 
My initial post was getting long so I didn't mention that I was creating a slightly more accute edge, and that after the first ten hours or so I did try adding a little more pressure, (slightly more than the weight of the knife) still could not believe how long it took!

I just didn't want to rush it since I was hoping to get amazing end results. But what happened was I started with a knife that would shave somewhat easily, and ended up with one the barely removes hair with effort... very frustrating considering all the time and effort I put into it.

Funny because pryor to this knife I had gotten some pretty good results in a heck-of-a lot less time. ...Maybe the hardness of S30V has something to do with it???

I just can't figure what I'm doing wrong??
 
It took me 30mins to regrind my Byrd cara cara from a low hollow grind into a high flat grind on a belt sander :p.

I've formed burrs with a belt sander, if you're going at an low angle it is okay to put a bit of pressure into it, if you're going at a higher angle then do less pressure.

Mark your edge with a permanent marker, then sharpen to see if you are actually reaching the edge, if you aren't hitting the edge then raise the angle OR put more pressure(only if you are happy with the current geometry, if it's too thick, then keep going at it).

When you hit the edge, sharpen and raise the grits till you get to a strop, and after your done, do the thumb nail test(try to see if it grabs on your fingernail), if it grabs at all points of the edge then you have successfully sharpened the whole edge.
After that drag the edge across your finger nail(like if you are trying to slice it), if it feels as smooth as glass, then you've polished it properly, if you feel it bite slightly into your nail like as if it was serrated, then you have not fully polished that area and need more work on the strop or a lower grit abrasive.
 
Funny, I did the sharpie marker trick at the start, but it all came right off even though I could see, and feel that the edges didn't quite meet.

I've found that in the right light, I can see the edge, and keep track of the dull spots by looking at the light that glints off of it...

Does anyone else do this??
 
BryFry said:
Funny, I did the sharpie marker trick at the start, but it all came right off even though I could see, and feel that the edges didn't quite meet.

I've found that in the right light, I can see the edge, and keep track of the dull spots by looking at the light that glints off of it...

Does anyone else do this??
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If you see reflections on the edge that means you have not sharpened the edge into a point yet and you need more work at a low grit.
 
I find that the sharpie test is good to find your angle, but to really sharpen, you have to get to a burr. the nice thing about a mousepad, in my opinion, is it absorbs much of the pressure you use. I start with 220 grit if I need to re-profile, or fix a really damaged edge. If you are using 180, and haven't got a burr after 25 hours, push a little harder. Personally, I use only three grits if the edge isn't totally chewed: 400, 600, 1500. After that, I strop with .5 micron green chromium oxide paste on leather. My buddy made the strop for me with a wooden paint stir stick and some Tandy leather. I only start with the 220 for really dull blades. So far, i have had really good results, and I keep improving. Just use less pressure with each successive grit, and work to a burr, and you should see rapid improvement.
 
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I've had surprising results with a dremel and a flap wheel for it. Followed by some sandpaper and a strop.
 
One of the primary reasons not to apply heavy pressure is that you compress the stropping "mouse pad" and hence it curves around your edge and makes it obtuse. The solution is to use a stiffer strop support. You might use a quarter inch thick board supported at the ends. When you strop hard the board will curve smoothly and not wrap around the edge. Using this method I would work one side of the blade for 50 hard strokes then flip it over and do 50 hard strokes on the other side. Keep this up with your coarsest grit until you basically start to get an edge. Now switch to your next finer grit and strop alternating sides until you get a rough paper cutting edge. Now go back to what you were originally trying with light pressure on a softer strop support.
 
Jeff Clark said:
One of the primary reasons not to apply heavy pressure is that you compress the stropping "mouse pad" and hence it curves around your edge and makes it obtuse. The solution is to use a stiffer strop support. You might use a quarter inch thick board supported at the ends. When you strop hard the board will curve smoothly and not wrap around the edge. Using this method I would work one side of the blade for 50 hard strokes then flip it over and do 50 hard strokes on the other side. Keep this up with your coarsest grit until you basically start to get an edge. Now switch to your next finer grit and strop alternating sides until you get a rough paper cutting edge. Now go back to what you were originally trying with light pressure on a softer strop support.
Click to expand...


...this makes sense to me, I think I'll try it.

I was just now messing with the knife doing some test cuts, it goes through paper ok, but I was having real trouble getting it to shave hair.... then I made a discovery... If I hold the blade at a normal cutting angle I get nothing, but if I tip the blade up toward the edge at a steep angle, it bites in and shaves much better.

I'm thinking this means that the edge is still much too obtuse. So even though I've got way too much time into this already, looks like I'm starting over again. (my wife is going to hate me)

-But at least I've got some time to kill. I'm off work since I accidently severed my achilles tendon with my freshly sharpened Fallkniven Thor bowie that I dropped on my self! -at least that knife turned out plenty sharp!
 
Jeff Clark said:
One of the primary reasons not to apply heavy pressure is that you compress the stropping "mouse pad" and hence it curves around your edge and makes it obtuse. The solution is to use a stiffer strop support. You might use a quarter inch thick board supported at the ends. When you strop hard the board will curve smoothly and not wrap around the edge. Using this method I would work one side of the blade for 50 hard strokes then flip it over and do 50 hard strokes on the other side. Keep this up with your coarsest grit until you basically start to get an edge. Now switch to your next finer grit and strop alternating sides until you get a rough paper cutting edge. Now go back to what you were originally trying with light pressure on a softer strop support.
Click to expand...

That's genius!
 
SUCCESS ...well kind of,

So I started over, this time using smooth maple plywood as backing, I used 220 grit and moderate to heavy pressure until I formed a burr, then repeated on opposite side.

Then I went back to leather backing and worked through up to 2000 grit using very light pressure. And finished with the strop.

This process took me around 3-4 hours, and the final result is...

-A nice looking edge that is functionaly sharp, but not impressively so. It cuts, but still not as well as it did when I used flat DMT stones.

For some reason even though I formed a burr, then gently progressed through the finer grits, the edge still has a thin visible hair line right at the edge, where I can see light glint off and can thus see that the edges still are not quite coming fully together! ...except for the curved "belly" of the blade, that part is fantastically sharp!

Still not sure why I can't seem to get the whole edge this way ...*sigh*
 
Your results are not unusual. I would go back to a fine flat hone and do a few very light edge forwards strokes at a slightly elevated angle to remove the burr. Then go back and strop a little more lightly.
 
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