Selecting grind profile based on sharpening technique

O

olddogrib

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Apr 18, 2011
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I realize expected usage is probably a more important consideration, but I assume certain grinds are more compatible to particular sharpening methods also. I can free-hand tolerably and have the stones to do it, but my primary sharpening method is a guided system (i.e. Lansky, KME) merely because I can maintain a more consistent angle. I know they can be a pain when your preferred (or the factory) angle isn't an option ( something other than 17, 20, 25, or 30 degrees), but some systems are now adjustable. What I want to know is a particular grind(s) more compatible with these systems? I'm guessing full flat (Scandinavian?) or concave (hollow?) would be logical choices if one doesn't care to change to profile. Am I off base? I occasionally "touch-up" on a paper wheel and I assume the concave is better suited for that. I'm still learning the proper blade to wheel angle though, and have rolled a lot of razor edges trying to get perfection. I'm also aware there's always going to be a trade-off between ease of sharpening and edge retention.
 
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I'm a little confused, are you asking about the angle of the edge, or the type of grind on the blade?

Because I don't think the blade grind has much to do with how it's sharpened, unless it is FULL convex, or scandi. Although I guess if you are using a guided system that requires you to secure the blade in some kind of clamp, it will be easier to do that with a saber ground blade since you have an even flat erea at the spine to solidly and evenly secure that clamp.

As far as choosing a knife based on factory edge angles, I don't take it into consideration since I find that I am not happy with about 80% of the factory edges I've seen, and usually the first thing I do with a new knife is reprofile it to my liking.
 
I'm a newbie and may not be using the proper terminology. I have blades that I may elect to maximize sharpness over durability by choosing an angle of say 17 degrees. It is not unusual to do a considerable amount of work only to find you're still removing metal at the bevel and haven't even reached the true edge( I occasionally dumbed it up and sharpened the clamp jaws, too!). I guess I'm asking due certain grinds minimze this by removing more metal in the cutting of the primary bevel (or establishing it further up the blade) so that if you choose 20 degrees you know you'll be removing metal at the edge. I used to could see this, but my eyes are gone!
 
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OK, I think I get it. You are talking about how much work it'll take (i.e. how much metal needs to be removed) to reprofile an edge to a more accute angle?

In that case it may be slightly easier on a hollow ground blade than it would on say a thick convex or shallow flat saber grind. Usually "most" full flat ground blades are by nature a bit thinner at the edge and shouldn't be too bad.

I think when it comes to reprofiling an edge choosing the right grit or method of initial stock removal is key to the ease and speed of the job. For example, if I am going to do a serious reprofile on a thick V edge I will often start with a 12" bastard file to quickly knock off the shoulders of the previous edge, and rough out the basic angle of my new edge before switching to a progression of finer grit sharpeners.

The file can also work for convex edges but is a bit trickier. But it's easy to simply start with a sufficiently coarse grit of sandpaper and stick with that grit untill you have achieved the desired edge angle you want before going to you finer grits.

...Hope that makes sense. :)
 
BryFry,
You got it, thanks. I've got some coarse diamond hones that will remove a bunch of metal in a hurry, so I guess I'm just lazy. 17-20 degrees is probably too acute for most purposes anyway, but I can sit around and shave my arms when I'm bored!
 
Richard J,
Just checked and the motor on my paper wheel is 3/4 hp and 3450 rpm, which is a bit faster than your recommendation. Is that good, bad, or makes no difference?
 
Pay careful attention to how thick the edge is right behind the sharpening bevel. Use a micrometer if you have one, or just compare two knives and try to see the difference. The grind style doesnt matter so much. The thicker the edge is behind the bevel, the longer it will take to cut a new bevel. I've seen knives that were 0.005" thick behind the edge, before the sharpened bevel ever started. These were very easy to sharpen and rebevel. I've also seen hollow ground knives that were 0.025" thick behind the bevel, 5x the thickness of the first knife. These take longer to rebevel, no matter the steel. When using the clamp systems, be very careful about the bevel setting. That angle is the angle to the edge of the jaws or some other fixed point. Knives wider than that fixed point will get sharpened at thinner angles, even on the same angle setting. The opposite is also true. Narrower bladed knives (width from spine to edge) will get sharpened at higher angles, even on the same setting.
 
olddogrib said:
Richard J,
Just checked and the motor on my paper wheel is 3/4 hp and 3450 rpm, which is a bit faster than your recommendation. Is that good, bad, or makes no difference?
Click to expand...

Slower would be better, the steel won't heat up as much and prvent damage to the heat treat as well as give you a bit more control. It would also be safer.
 
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