Full convex grind - ?'s on rust and HT

Richard, thanks for the advice! Much appreciated.

Stacy, you need to have a little more faith in me! Just kidding. I seriously didn't know that maintaining a full convex was a challenge! I was planning to maintain it (as I've seen in some videos) with sandpaper over a mouse pad and a leather strop. This is my first convex edge of any kind (first hand made knife, period). I do have a little Muela skinner, but I have no idea how they are manufactured. ANYWAY, I want to give the full convex a swing - do you guys recommend a different method of maintenance?

My understanding is that if you put the whole width of the blade to the paper at each sharpening, you won't develop a secondary bevel. True?
 
bladsmth said:
Not wishing to get into a detailed discussion, but the OP is an inexperienced maker who is making a chopper. That is a world away from an experienced togishi and a kitchen slicer. With limited equipment and experience it would be a long shot for the OP to maintain a full convex grind.
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Ok I see where you are coming from.
 
Well, Gentlemen. Enlighten me before I HT. What's so difficult about maintaining a full convex?
 
M3mphis said:
Richard, thanks for the advice! Much appreciated.

Stacy, you need to have a little more faith in me! Just kidding. I seriously didn't know that maintaining a full convex was a challenge! I was planning to maintain it (as I've seen in some videos) with sandpaper over a mouse pad and a leather strop. This is my first convex edge of any kind (first hand made knife, period). I do have a little Muela skinner, but I have no idea how they are manufactured. ANYWAY, I want to give the full convex a swing - do you guys recommend a different method of maintenance?

My understanding is that if you put the whole width of the blade to the paper at each sharpening, you won't develop a secondary bevel. True?
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Yes, this method will work well, ...and I will have more faith in you.
One of the problems with giving advise on-line is you have to gear it for the complete newbie, or someone will say, "Oh, Stacy/Bill/M3phils said that all you need to do is........, and make a terrible mistake because they dd not fully understand the process.

When sharpening a full convex edge, it is necessary to carefully watch the edge as it is removed, as the dull areas are removed at the same rate as the still sharp areas. If not careful, the edge and sides may develop some curve or ripple to it. Obviously a mirror polish is not the best choice for this, which is the problem with re-sharpening a katana/wakizashi , which can be ruined by improper self-sharpening ( and why they are usually sent to a professional).

To touch up a convex edge, I use my slack belt , running at its slowest speed with a 400 grit belt. Place the blade on the belt , at an angle that just keeps the main surface off the belt. Lightly run the edge across the belt. Flip and repeat. Check the edge to determine how well the burr is forming. When it is even, and the edge is straight, buff off the burr and you will have an incredibly sharp blade.

As I said to Bill, this edge type can be maintained by a few quick strokes on a fine stone at a very low angle. I have a friend who loves full convex grinds, and sharpens them by placing some metal AC duct tape on the knife side, up to within 1/4" of the edge. He then sharpens them on the stones without fear of scratching the sides, and only removes the edge metal and a little tape.
 
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Great tips, I appreciate it!

Hopefully, my dad and I will get together this weekend and HT a few knives.

I'll update this to let you know how we do!

Thanks again.

Matt
 
As was said, drill the pin holes before heat treat!!!

So much easier to do while the material is not hardened.

The shape and blade profile looks great.

I did a back yard heat treat with 5160 with hardwood charcoal, and a magnet to check for non magnetic before quenching in oil, then tempering in the oven.



Nothing intrinsically wrong with a full convex grind. They are awesome.


I convex all my users. It is not rocket science to maintain the edge. If you have the knowledge to grind one, you certainly have the knowledge to keep it sharpened.

It is not rocket science. Don't even need a belt sander to get the job done.
 
Thanks guys for the tips. I hardened the blade earlier today. I think it went pretty well. A file doesn't do a thing to it! I still need to temper it, grind to an edge, and finish sand. Then handles.

It was kinda funny. I put a pair of vise grips all the way back on the pommel. I thought, "I'll pad this so that I don't leave vise grip teeth marks." I threw a folded up piece of canvas in there. Well, it didn't take long for the heat to conduct all the way there and, yep, fire. I wasn't going to lose my heat though, so I just kept at it and let it burn.

Here's a pic. In the pic you can just make out the hamon line. I threw some 550 cord on there just to get a better idea of how it will look with scales.

You'll notice that hole I drilled in the bottom of the ricasso (I don't know if you'd call that a quillon or not) is a little bit off. Bummer. I thought I had it. I even dented it before drilling.

Thanks again for the help.
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I don't know what the line is, but it is not a hamon. 5160 has too much alloying to form a hamon. I suspect you did a partial quench, and that is the quench line.

The knife looks good, and should serve you well.
 
Thanks again for all the help.

If you're still following this, I thought I would update you real quick.

Blade's been HT'd, finish sanded, sharpened. Looks great.

This evening I chopped some 2x4 and stripped my Christmas tree (still in back yard - specifically for this purpose :) ) of all bark and branches. The knife works great. I wailed on it a few times - no chips, rolls, or ANY damage. Still sharp. This is shaping up fantastic.

Over the weekend, we got out and found some dead bitter brush. I'll see if any of it is fully cured soon. If not, I've got two chunk of ironwood. I'll put up some photo's when I get it completed.
 
M3mphis said:
Oh yeah. I also need some brass tubing. I have pins, but I'm going to do two pins and a third with a tube for a lanyard. Haven't picked up the tube yet, so I don't know what diameter to drill the third hole.

Thanks for the reminder.
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I use copper plumbing pipe, the small stuff that is usually run to a refrigerator for the ice maker. I has an OD of 1/4" and is sold by the foot at the hardware store.

- LonePine
Alias Paul Meske, Wisconsin
 
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