Convex edges - pros & cons?

Cliff - I do agree with what you're saying.

Just re-read my post above.

There is still a small area similar to a microbevel, but where a microbevel has a sharp turn in angle, the convex edge is smooth = only difference.
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This is the same thing as what you described Mel doing to his blades.

I maintain that even with a "lift" at the end of your stroke, you still have a convex edge with no true micro-bevel to it.

The advantage is the same: Final grind angle = wider.



Also, the comment made earlier about blades wearing down over time being a disadvantage to a convex edge is nonsense. That happens with whatever knife you have (excepting those made with 1/16" steel with only a micro-bevel....a rarity). Any blade with any kind of taper to it is going to get thicker, the more material you remove.

Which brings me back to a sub-advantage for the convex edge - by stropping, you are removing less material. Only steeling/burnishing is better. CrOx is 5000 grit, and if you use finer powders, you can get ~10-12,000 grit. One of the great benefits of stropping is the edge-trailing effect. You are massaging the edge back into place....re-aligning it.....rather than removing steel to reform the preset bevel.
 
Older CS Trailmasters and SOG Tigersharks were advertised as having a "rolled edge". Is this a term for convex edges?
 
Convex edges have an advantage in strength if you are going to chop relatively hard materials. It is also usually easier to pull a convex ground blade out of a heavy cut into wood than other contours. A convex edge makes a lot of sense on a bolo machete or a hatchet.
 
From what I have read here and on the Dozier Forum I do not believe that this discussion will ever be resolved. In the first instance you have to resolve the differences between a convex edge grind and a convex ground knife. It might be a moot point but you can put a convex edge on a hollowground and a flat ground and you can put a flat ground edge on a convex ground knife. To my way of thinking there is no such thing as a hollow ground edge except maybe on specialist tools.

It really comes down to horses for courses and each individual will determine what is the best edge for a specific task. I will stick to my original thinking on this in the Dozier Forum - the flat ground knife with a flat ground edge is the best design for Mr and Mrs Average. A hollowground blade (properly done) is more suitable for the advanced knife user and for specialist tasks. And, from where I sit leave the convex grind for axes and specialist tools.
 
rolled edge - called that because you knock the burr off (roll it) as a second-to-last step to sharpen it. You can roll the edge on a buffer. You can also just drag the knife across hard wood to take the burr off. After that, you strop it.
 
pendentive said:
rolled edge - called that because you knock the burr off (roll it) as a second-to-last step to sharpen it. You can roll the edge on a buffer. You can also just drag the knife across hard wood to take the burr off. After that, you strop it.
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Thanks, but, um.....I don't think we're talking about the same use of the term. I have seen in a number of different places "rolled edge" used interchangably with "convex edge" as if the terms are synonymous. Besides Cold Steel and SOG, I have seen this at Fallkniven.
 
A rolled edge is not necessarily a convex edge. If those knives have convex edges, and they are calling it a rolled edge, it is being used in a slang/street way.

Convex edges can be created using the "rolled edge" technique.
 
pendentive said:
rolled edge - called that because you knock the burr off (roll it) as a second-to-last step to sharpen it. You can roll the edge on a buffer. You can also just drag the knife across hard wood to take the burr off. After that, you strop it.
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Oh...wait. Now I understand your answer. The answer is yes, and the reason is stated in your answer above. Thanks.
 
Convex edges have no advantages becuase of :

1) stropping as you can do that with a flat edge just as readily

2) wider / more acute profile as that has to do with the implementation of said grind

In regards to losing material, planing down the entire blade flat induces a much larger change in blade properties than removing material from the edge, especially considering that strength isn't linear in blade thickness.

There is however an advantage to hitting the primary grind with each sharpening, as you will never need to apply a relief grind. However it is pretty inefficient to do this every time you sharpen, unless as noted in the above :

1) there is a lot of surface damage you want to remove

2) the blade is so easy to machine, or your skill so great or you have enough free time that the increase in time doesn't matter anyway

-Cliff
 
Cliff, how about the purest criterion for a blade, cutting ability? I did a little testing of my own, using a Queen D2 muskrat- 2 of the same blade. Blade A got a normal sharpening, 15 degrees per side on the Sharpmaker, then sandpaper up to 1,200 grit. Side B had a convex edge put on, using mousepad and a wooden wedge with a tin face (actually, it was a piece of leftover tin that I Gorilla-Glued on) to ensure a 15 degree edge per side.

Side A cut 45 feet of corrugated cardboard before stropping was ineffective. Side B cut 122 feet of the same cardboard, in the same manner, prior to sharpening. Resharpening took about the same period of time. The etch is still extant on Side B, which was convex.

Why should I ever do a V-grind again?
 
What exactly was being compared, if the angle was 15 degrees in both cases how was the second convex?

Was the final grit in both cases the same? Was there some kind of stropping done to the Sharpmaker finish?

When you "made the second blade convex" did this involve altering the primary edge profile, ie. adding a relief grind?

Have you switched blades to check that it isn't the knife itself that is performing different?

You might also want to do blind testing to check for user bias, as well as repeatabilty. Blunting is a nonlinear process, so even small initial changes can induce large changes in run length (2x or more).

Are you stropping on both to check for resharpenability - then of course this is more responsive to the convex one because that is the inherent shape of the blade, you would want to check with the Sharpmaker on the one which was finished with the Sharpmaker.

Were both blade initially at idential levels of sharpness?

-Cliff
 
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