Help with Convex Edge

rod tak

rod tak

Joined
Feb 9, 2010
Messages
352
Hey guys, I have been trying to get a convex edge on my Izula for weeks now, and i don't know what I'm doing wrong. I've gone through all the steps, I'm getting it polished but its just dull.

I'm going from 400 grit/600/1000/2000...than stropping with chromium oxide. It looks great, completely convex and a mirror edge...but It's dull.

Any suggestions?
 
If its still dull after all that, you either have a very stubborn wire edge or you never actually got to the edge. Run the blade in a stropping motion over some sort of fuzzy cloth. If there is a lot of stuff stuck to the edge after doing this on both sides, you still have a burr/wire edge. You'll need to get rid of it using your method of choice.

If that doesn't work, color the edge with a magic marker and take a few sharpening strokes. Look at the edge with good light and 3x or 4x magnification if you have it. If you see a tiny line of ink along the edge, you haven't reached the edge yet and have just been polishing the bevels, not sharpening. Start with 120 or 220 grit wet/dry, use some water or oil, and work down from there.
 
What me2 said. I'd bet that most likely your edges are not fully coming together.

There is also a chance that you may have rounded off the edge if you are using too much pressure. So be sure and use a light touch.

Under a good light source you can actually see the edge, and the more of a hairline glint you can see at the edge, the more you need to work on bringing those two edge angles together. -A "perfect" edge will have NO visible glint of light that is seperate from the rest of the edge, because the edge is continuous to a zero point where the angles meet.

Good luck, and keep trying!
 
No, i don't think i did work until there was a burr. Usually my sandpaper goes before i can get there.
 
I dont know if you have any available, but if you are just looking for a convex edge, you could try using 1x30 belts stretched tight and used like a stone. I sometimes hook a 120 grit 1x30 belt around the corner of my vice, use a large C clamp to make a handle, and stretch it out. Then I sharpen/rebevel my knives. It takes some practice, and you will end up with a pretty wide bevel, but I used this method to put full convex grinds (not just edges) on the blades of my old Schrade Peanut. Started with 80, then 120, 220, 320, then switched to wet/dry strips 1" wide clamped to a table and stretched tight all the way down to 1500, followed by stropping with a strip of leather clamped and stretched. It was my first hair whittling edge. I just laid the blades flat on the stretched belt/paper and went to work. Took a few hours, but did the job. Careful if you try this way, as it will round the tip quickly if you're not careful.
 
If you have been working at this for weeks, and going through sandpaper, I can't imagine that you haven't gotten to the edge yet. I'm pretty sure you are rounding your edge. It's almost impossible not to do that with "oversharpening". If you just keep on sharpening a blade freehand, it will almost certainly blunt. It's the inaccuracy of being human. It happens to just about everyone. The more perfect your technique, the longer it takes to "oversharpen". If you've been working for weeks, it seems like this can be the only answer.

You will have to go back to the beginning and start over. Be very careful and deliberate with your 400 grit. Sharpen until you get a good clean edge that will cut paper pretty cleanly. Don't go to the next grit until you have a sharp edge. If you can't get a sharp edge with 400, your technique is the problem. As you've heard, too much pressure is a likely cause. It's either that or you aren't maintaining your angle consistently, and I don't think there are other variables.

Next, you would be much further ahead with better grit selection. Go 400, 800, 1500. By doubling the grit, you maximize efficiency. What you are really trying to do is erase the previous grit's scratches in as few strokes as possible. Remember this; More strokes lead to more mis-strokes. That's the whole issue in a nutshell.

You should be shaving at 800 grit. Maybe not cleanly pushcutting, but very close. If your edge isn't sharper after 10 or 15 minutes at 800, you will have to start over. It may take longer than that to remove all the 400 grit scratches, but not a whole lot longer. if your blade isn't getting progressively sharper every ten minutes, you need to change something in your technique. You don't say what kind of backing you are using, but generally, the softer the backing, the lighter your touch needs to be, or you will be rounding your edge.

Remember, you are really trying to get the acceptable degree of refinement in as few strokes as possible, and you can't switch grits until you get your blade sharp at the lower grit. If your blade isn't shaving cleanly at 1500 grit, no amount of stropping will get it sharper. Stropping will take you from shaving to hair popping.

These are just my humble opinions, nothing more.
 
Great points above.

Also, you probably won't create a burr with your technique, you are probably rounding the edge off.

My 2 main points:

Work really slow.

Use really light pressure.
 
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