New to convex sharpening

J

Jo Jo

Joined
Apr 2, 2008
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23
I've watched all the youtube videos and done the reading, now I'm working on my skill, I can cut paper like never befor, the edges are really sharp, don't ask me how I know, but I can't shave hair, why not? Thanks Joel
 
I'll be watching this post closely because I'm new to convex sharpening as well and am having the exact same problem with my Marbles knife. It's sharp but will not shave. What's up with that?:confused:
 
you might have a large burr. try stropping on a very fine abrasive to remove the burr.
 
I never have gotten a burr while convex sharpening any of my knives, at least, not that I could ever tell.

I've asked the OP's question before and, after I learned how to convex sharpen, I've responded many times to try and help with what little knowledge I have.

Now it occurrs to me that I really don;t know how to help someone unless he and I are together and can watch each other. I mean to say that it's so difficult to give advice if you can;t see what the person is doing or not doing. I know that sounds defeatist, but it's occurred to me.

Jo Jo, below is a picture of the setup I use that works for me. About the only points I would say to make sure you're doing is:
- don;t use grits lower than 800 or 1000 unless your knife is truly dull or you're working your way up through the grits from about 220 after trying to repair a nicked or rolled edge;
- keep your pressure very light (lots of strokes are the key to success for me);
- keep your angle low (better too low and raise little-by-little than too high);
- each convex edge has its own "sweet spot" as far as angle goes;
- pay particular attention to the belly. I find myself almost always raising the angle a degree or two through the belly up to the tip;
- strop on loaded leather using the same guidelines.

I hold my wet/dry "strops" (and my leather strops) in my left hand - palm up with fingers gripping the edges. With my right hand, I strop to sharpen. I can adjust the angle of attack with either hand. Most times, I'm adjusting ever-so-slightly with both hands at the same time. Don;t give up, it'll come to you.

One more thing: lately I've been taking my convex edges to the 6" grinder to strop on a muslim wheel loaded with white. I DON'T RECOMMEND THIS until you feel very comfortable with getting your edges sharp with wet/dry and leather stropping, because it's very easy to end up with a knife that is duller than when you started! But I say it because I think Richard J is recommending the cardboard or paper wheel stropping (I didn't follow the link Richard, I'm just guessing that's what you advocate). I haven't tried this system but, after learning how to buff/strop on the grinder, I'm leaning toward trying the cardboard method.

convex-01.jpg

convex-02.jpg
 
after 38 years of sharpening everything from tool bits for a lathe to exacto knife blades for my nephew, you learn a thing or two along the way. i have seen and or tried many gadgets and even came up with quite a few of them myself but for my own use. if there was a way to get a quicker better edge i would be using it instead of the wheels.
 
I want to get a set of the wheels, Richard, but the price is holding me back. I know it isn;t all that much, but you know how we do: we prioritize and I just haven't taken the leap. I've been thinking about trying to make my own, but I haven;t yet.
 
Stretch, do you have something soft under those sandpaper strips, like a piece of leather or mouse pad? Convexing with sandpaper is a lot easier with a soft backing.

And I agree with richard 100%! The wheels are the bomb!
 
I just tried the mousepad method for the first time and I couldn't shave either, so I knew there had to be a burr.

I put the dremel in a vice and attached a 1 inch polishing buff and some white compound, a couple of quick passes and viola...

now it easily shaves arm hair with no effort at all.

paper doesn't stand a chance, it is easily the sharpest I have ever made anything

thanks to whoever invented this method.

kyle
 
stretch, dont attempt making your own wheels. its not safe for one and isnt too smart an idea. it never should have even been suggested :rolleyes:. the wheels are made of a special paper and they are made for high speed. it only takes once for a piece to come loose and become a projectile that could cause the loss of an eye or even death. i thought the same thing until i though of what could happen. its not worth taking a chance and getting hurt. i'm not saying this to keep you from making a set and instead buying them, i'm just looking out to keep anyone from getting hurt ;):D.
 
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stretch, I've gotta agree with richard on this one...these wheels are made completely different than what you'd think. After seeing them, I know I could never make anything like this, even given the proper raw materials. It would almost be like trying to take sandpaper and duct tape and make your own sanding belts.

That would be dangerous. For your own safety, don't try it.
 
Allright fellows, I won;t make any. I do want to try a set though, because if I understand the concept correctly, the cardboard or paper wheels take care of the whole sharpening process, not just the stropping (except of course, I'm assuming, if the knife is overly dull to begin with and needs a good wet/dry sharpening to begin with).

SPX: yes, the wet/dry strops are approx. 3" x 11" x 1/2" either mahogany or mdf. Then I glue a nice piece of 7-8oz or 8-9 oz on. Then the wet/dry gets taped at the ends over the top of the leather. My compound strops are made the same way.
 
StretchNM said:
...if I understand the concept correctly, the cardboard or paper wheels take care of the whole sharpening process, not just the stropping (except of course, I'm assuming, if the knife is overly dull to begin with and needs a good wet/dry sharpening to begin with).
Click to expand...

Correct. The grit covered wheel will raise a burr almost instantly, and then the slotted wheel removes it just as fast. The kit even comes with the wax and rouge you need.

These things are great, and the learning curve isn't bad at all. I took a handful of old dull (and I do mean dull) kitchen knives and had them paper slicing sharp in just a few minutes!
 
if anyone is wondering why the kit comes with wax, it helps keep the heat down. its a special blend of wax just for the wheels.
 
Thanks for all the advice. I like the wheel concept, something about a sharp knife, must be a guy thing. I realized I didn't give any info on what I was doing.

I use sandpaper on a mouse pad, grits from 120 for the worst blades, to 2,000 for the final step. I have not gotten the leather strop for finishing. I feel no burr on the edge. When do I develope the burr? Am I suppose to start on a stone then switch to the sandpaper?

Thanks for the help, Joel
 
if you aren't feeling a burr at 120 grit then you should keep sharpening. once you get the burr, all you are doing is polishing the edge more, to make it cut better.

before i got my sander, when my edges were really bad i would sharpen them on a coarse stone and then use sandpaper to convex and polish them.
 
Joel, work on one side only until you feel the burr, then move to the other side. If you're alternating sides, you'll never get a burr to raise. 120 should most definitely raise a burr! If you want a convex edge, stick with the mouse and sandpaper the entire process.
 
I've been having some convex trouble as well with my Northstar. I suspect that my backing material was too soft and my my angle was too high. I have switched to a firmer backing and lower angle, and there has been a little improvement, but nothing like the original Barkie edge.

The odd thing is, I have no problems with my Mini Canadian - just my Northstar.:confused:
 
StretchNM said:
I never have gotten a burr while convex sharpening any of my knives, at least, not that I could ever tell.

I've asked the OP's question before and, after I learned how to convex sharpen, I've responded many times to try and help with what little knowledge I have.

Now it occurrs to me that I really don;t know how to help someone unless he and I are together and can watch each other. I mean to say that it's so difficult to give advice if you can;t see what the person is doing or not doing. I know that sounds defeatist, but it's occurred to me.

Jo Jo, below is a picture of the setup I use that works for me. About the only points I would say to make sure you're doing is:
- don;t use grits lower than 800 or 1000 unless your knife is truly dull or you're working your way up through the grits from about 220 after trying to repair a nicked or rolled edge;
- keep your pressure very light (lots of strokes are the key to success for me);
- keep your angle low (better too low and raise little-by-little than too high);
- each convex edge has its own "sweet spot" as far as angle goes;
- pay particular attention to the belly. I find myself almost always raising the angle a degree or two through the belly up to the tip;
- strop on loaded leather using the same guidelines.

I hold my wet/dry "strops" (and my leather strops) in my left hand - palm up with fingers gripping the edges. With my right hand, I strop to sharpen. I can adjust the angle of attack with either hand. Most times, I'm adjusting ever-so-slightly with both hands at the same time. Don;t give up, it'll come to you.

One more thing: lately I've been taking my convex edges to the 6" grinder to strop on a muslim wheel loaded with white. I DON'T RECOMMEND THIS until you feel very comfortable with getting your edges sharp with wet/dry and leather stropping, because it's very easy to end up with a knife that is duller than when you started! But I say it because I think Richard J is recommending the cardboard or paper wheel stropping (I didn't follow the link Richard, I'm just guessing that's what you advocate). I haven't tried this system but, after learning how to buff/strop on the grinder, I'm leaning toward trying the cardboard method.

convex-01.jpg

convex-02.jpg
Click to expand...

How much give does the leather actually give though? I find that unless i push down allot of pressure, i mite as well glue my sandpaper to a piece of wood. The mousepad doesnt give much either though. I am not understanding the whole "underneath give" thing. If you can help me i would appreciate it
 
mrbladedude, try a phone book under your sandpaper. it works better than a mousepad which i think has too much give.
 
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