Sharpening Question

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Mar 26, 2005
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I have been playing around with my new Edge Pro and had a question. I sharpened my SFNO at about 21 degrees per side. The edge slices news paper with ease and shaves smoothly, but is this edge going to be durable enough for general outdoor use?

Can I sharpen my HOG FSH at this same angle?

Thanks for the help. :D
 
Congrats on your new Edge Pro Peter! Great sharpener eh? Just flat out really like mine. What model did you get?

The edges I've put on my blades have held up really well. I do have to maintain them with a smooth steel, every now and then but it doesn't take long to bring them back to razor sharpness. I even have a smaller smooth steal to take camping with me. You can find some really nice ones at handsamerican.com

I'd have to say that the V-edge isn't a strong as a convex, but the sharpness is as good if not better, IMHO. The V-edge will roll faster than a convex without a doubt so you will have to maintain it more often than you would a convex edge, but it isn't hard to do.

Hope that helps.
 
Thanks. :D

I got the Apex Complete kit and it works very well and is easy to use. :thumbup:

I have an idea for a smooth steel I am going to try and have made for me by a friend.

The polish tapes work very well, I heard you can use them for convex edges as well.
 
I’d go with that angle: IMO, INFI is tough enough to make up for any possible loss of strength in the edge.

Getting yourself a steel would probably be a good investment.

Really sharp edges make big knives more useful than they might otherwise be.
 
How would 24 degrees be for a heavy use HOG FSH? I am not so interested in paper cutter as I have a Wave on me for things like that.
 
Try it. You’ll gain useful experience with the sharpening system, and learn more about the performance of your knives in the process.
 
Solstice said:
I'd have to say that the V-edge isn't a strong as a convex, but the sharpness is as good if not better, IMHO. The V-edge will roll faster than a convex without a doubt so you will have to maintain it more often than you would a convex edge, but it isn't hard to do.

Solstice - how about a double angle edge? Would that be practical? Would that fall somewhere in between a V edge and a Convex edge as far as strength? Is a convex edge basically a rounded off double or triple angle edge?

Also, another question for you and Peter, or any other edge pro owners. When using thick bladed knives with various grinds, how does that affect the accuracy of setting the angle? For example, on a clamping system such as the Lansky, the blade is clamped equally on both sides and the edge remains centered. Doesn't the blade lay flat on the Edge Pro? If so, what happens with a thick blade with a full height grind that lays sloping downward? Bear with me guys, I'm still learning. :D
 
Update:

Ok, I just did a little comparative work with various sharpening angles.

EU-17 Magnum: 18 degrees per side
SFNO: 21 degrees per side
HOG FSH: 24 degrees per side

Each knife was used to chop through ten 2.5 inch deck nails, each of these were about 3 mm thick. These were full power chops into the nail.

The following details what happened to each after the impacts.

EU-17 Magnum:

After some of the impacts, the only result was a blunted edge. However, where two or more impacts occured close together, the result was a rolled edge. Most of these were about half milimeter into the edge and one of them was about three quartres of a milimeter into the edge. Most of the nails ended up looking like "L"s after the impact but fa few were chopped right in two. :D

SFNO:

Not all of the impacts resulted in a rolled edge, most just blunted it. The edge on the SFNO proved to be more durable than on the above. The rolled over sections of steel were all about half a milimeter into the edge.

HOG FSH:

The edge on this piece was only blunted, although the thick edge impaired performance in other areas: the thick edge required more force to slice through rope, newspaper and card board. This may also be because of the thickness of the spine.

So, I am looking for a sharpening angle somewhere between 21 and 24 degrees. The nails (hopefully) are pretty close in hardness to rocks so this is a fair test to see the results of accidental hard contacts with rock. Another thing, this test was not done to find a universal sharpening angle, just which angl is best in a purpose built chopper.

I am going to try and take some pics of the knives and the nails when I get home and have access to a camera.

Comments, suggestions?

Bryan, I have only sharpened V ground knives so far. Someone with more experience can better answer that question. For a convex edge, you can use the polishing tapes (they come with 1000 and 3000 grits and they really work well).
 
One other thing I should add, I did this same test with the NIB edges with a Becker C/U7, Cold Steel Kobun, and a CRKT knife (I can't remember the name). All of these knives suffered far worse damage. The edge just shaped itself around the nail so it looked like a serrated blade.

I guess it is not fair to compare these blades with a Busse, but the edges on these were thicker than the edges on the Busses.
 
Well done. Testing is the best way to learn how to get the best out of your gear.

I sharpen freehand, and it is years of experience that guide my hands into choosing and maintaining the right angle. It sounds like you’re on the way to developing these skills.
 
Common nails, what you get if you just buy nails, are really soft, less than 10-20 HRC, rocks can be harder than knives. However chopping into a nail is often worse than smacking a knife into a rock because the contact area on a nail is so small, and like you noted the edge can just fold around the nail, this is why screws are so bad to hit because the ridges focus all the contact on such a tiny area and the pressure skyrockets.

In regards to angle and cutting ability, note the only part of the edge that needs to be 20+ degrees is the part that is resisting the bend, so there is usually no need to have the entire edge at that angle. This means you can get better cutting ability with no functional loss in durability by applying a relief grind to the edge and cutting the shoulder back. This relief grind can be really acute, as in ten degrees.

It is also why you get less damage if you chop with a draw vs a straight smash, if you are so inclined try it with the nails again but include a draw, it may take some time to get the technique down, you may want to experiment with woods, grass actually works well to get the movement. What happens here is that the blade "sees" a greater size nail because it is getting drawn across it and thus the pressure is lower and the damage reduced. In general this is more effective at cutting anyway.

I noticed this when I was fooling with cutting some concrete blocks and found that I could vastly effect the amount of damage you could inflict on a knife by varying the technique. Which is one of the benefits of doing such extreme work, you generally learn how to things which most would consider really abusive without harming the knife. Of course it helps to have nice knives as well.

Interesting work in any case, strength isn't linear with thickness however cutting ability is linear so you have to in general trade a lot of strength for little cutting ability. Too bad it didn't work the other way. Note if you have to chop metals for whatever reason, it is best to do so on a rigid cutting board like mild steel, it is the bending of the nails that tends to damaged the edges.

It is also easier to baton and chisel them through, but here you were looking at accidental impacts, not how to cut nails which is best done by sticking a HSS hacksaw blade in your sheath.

-Cliff
 
Cliff,

That’s interesting about drawing the knife while chopping: I worked that out a couple of years ago, and wasn’t sure quite what I’d worked out.
 
Thanks Cliff for the tip on drawing the knife when chopping. If nails are too soft, what would you suggest as suitable testing material?

djolney, I'm getting there! :D
 
Nails are fine as they are small and thus focus the stress, if a knife hacks up those nails with little damage it has little to fear in use. What I would caution against is over protection. How often do you hit inclusions and work in dirty materials, is this a rough "tactical" knife or more of a utility piece. How much cutting ability are you willing to give up for a little less sharpening if you hit a rock.

I generally cut my knives so they will get damaged if I whack them into a rock, but make sure when I grind the edges I leave them thick enough so it won't blow the primary edge grind. I want the edge to be above 0.025" for chopping and 0.035" for really heavy batoning as in shoulder impacts with a several pound stick. I rarely grind them more than 15 degrees with a micro-bevel at 20.

One thing to note above reducing bevel angles is that you also generally reduce the force on the swing then as you don't need to use that much force, this also reduces the damage upon impact.

-Cliff
 
brianNH said:
Solstice - how about a double angle edge? Would that be practical? Would that fall somewhere in between a V edge and a Convex edge as far as strength? Is a convex edge basically a rounded off double or triple angle edge?

Hi Brian,

Sorry it took so long to get back to ya. I discussed this very point, double bevels, with Ben Dale in some emails. He agreed that a double bevel will add strength to your edge and it can come in handy when sharpening thicker blade knives. Part of the problem with thicker blade knives is getting a thin enough edge on them to make em razor sharp. After all we don't shave our face with 1/4" razor blades. With a double bevel edge you can have the secondary edge be your razor edge while having the primary edge behind it, adding strength to the secondary. This also is nice because you won't have to remove so much metal from the knife to achieve a nice thin sharp edge. A lot of the thinner knives, fillet & hollow ground, have incredible razor edges but we wouldn't go chopping 2x4s with them. Well must of us wouldn't. :D

Hope this helps.
 
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