What do I need to know about my convex grind knife?

B

Bridgeman

Joined
Oct 1, 2005
Messages
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Hello folks. As I have put in another post, I have picked up my first Blackjack knife and it has a convex grind to the blade. This is gonna sound like a real stupid question, but is there anything I need to do different when sharpening it? Traditionally i have honed the blade somewhere between 20-30 degrees.
Thanks,
bridge
 
Bridgeman said:
I have picked up my first Blackjack knife and it has a convex grind to the blade. This is gonna sound like a real stupid question, but is there anything I need to do different when sharpening it?
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Some sharpen the entire blade, thus the whole knife is ground on a stone. This maintains the taper however it makes sharpening a very time consuming process. If you are going to apply a secondary bevel then you sharpen it as you would any other knife, those angles are kind of high however unless you are using the knife for very rough work.

-Cliff
 
Thanks. I held the angle a bit higher to remove a minimum of steel. Actually I am asking this question after-the-fact, but it seemed logical to hone it like any other knife. The result is shaving sharp by the way. Just wanted to make sure I was doing it right. Additionally, I could not see the edge on the original grind. It is now visible. That's what made me wonder.

I am probably just going to keep this knife stored. The only reason I honed it was to remove three very small nicks on the cutting edge.
I appreciate the reply and any other advice anyone may have. The knife is a Trail Guide and pictures are posted in another post.

http://www.bladeforums.com/forums/showthread.php?t=426333

Thanks again,
bridge
 
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Bridgeman said:
Additionally, I could not see the edge on the original grind. It is now visible. That's what made me wonder.
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Generally such knives are often made using belt sanders and thus there is no distinct secondary edge bevel.

-Cliff
 
Thank you Dannyboy, that was some GREAT information. The links helped me to understand why I couldn't see the edge bevel. Basically it is a full convex grind and didn't have one! I feel a bit of a fool for putting an edge bevel on it, but truly prefer that to regrinding the entire side of the blade. As I stated above, I did it to remove a few very slight nicks that no one besides an engineer would have ever known were there. It is still a very nice knife and I would bet that the majority of users do as I did and only hone the edge.

Still, what an education. Thank you.

bridge
 
Bridgeman said:
Thank you Dannyboy, that was some GREAT information. The links helped me to understand why I couldn't see the edge bevel. Basically it is a full convex grind and didn't have one! I feel a bit of a fool for putting an edge bevel on it, but truly prefer that to regrinding the entire side of the blade. As I stated above, I did it to remove a few very slight nicks that no one besides an engineer would have ever known were there. It is still a very nice knife and I would bet that the majority of users do as I did and only hone the edge.

Still, what an education. Thank you.

bridge
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Bridge, You are very welcome, sir. Yes, I see LOTS of full convex ground knives that come across my leather workbench with secondary edges installed on them. This is fine, of course, if one is wanting a more toothy edge to satisfy his needs. I prefer the polished convexed edge for woodcraft and general field use, and in our ranch butcher shop, the toothy edge works best for meat cutting. Don't feel foolish for installing a bevel on your knife...you can change back without any problem. I have seen several full height convex grinds (even on expensive customs for example) where the owners ground the blade entirely flat because they simply didn't understand the geometry of the blade. That might be embarrassing.:D

I will often slightly convex the edges on my Scandinavian ground blades (if sabre ground and flat) to increase the cross section for added strength. Some of my thick flat ground blades also have convexed edges that greatly increase their efficiency for some tasks. Lots of sharpening flavors or options to choose from. :)
 
Well Dannyboy, I just hooked up a mouse pad with some 1500 wet and I am sure I rounded the edge of that bevel a bit back toward the convex. I didn't think it possible but I believe it got a bit sharper. I maybe should have hit it with some 400 or 600 first, but I didn't want to over react. Basically this is a collector. Now I am going to try the technique out on another knife. I'll let you know. :) I'm all set up at the kitchen table. Wife loves it.

bridge
 
Bridgeman said:
Well Dannyboy, I just hooked up a mouse pad with some 1500 wet and I am sure I rounded the edge of that bevel a bit back toward the convex. I didn't think it possible but I believe it got a bit sharper. I maybe should have hit it with some 400 or 600 first, but I didn't want to over react. Basically this is a collector. Now I am going to try the technique out on another knife. I'll let you know. :) I'm all set up at the kitchen table. Wife loves it.

bridge
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Wonderful! The 400 would get you there fairly fast...and as always, the easy-does-it approach will work best. It is easy to press too hard into the mouse pad which will allow the abrasive paper to move up onto the edge wearing away your efforts. The paper needs to follow the grind, rather than wear it away, too. I usually finish up on 1500 and then move to blade honing compound (on a strop) for a final mirror polish. Amazing how sharp a good convexed edge can be!:) My leather cutting knives (head and round knives) have polished convexed edges too. These tools just sail through the thickest of saddle skirting.

Something about those kitchen tables, eh?:D Though I have a nice shop, garage, and barns; I still find myself at that kitchen table.:jerkit:
 
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