Advice on convex or v-grinds for edge maintenance

[maximus83]

Question for sharpening pros: For myself as a non-pro sharpener who has been doing all right with v-grinds, is it worth going down the road of trying to learn a 2nd type of grind (convex) and how to sharpen and maintain it well with my tools?

Background: Like many others on this forum, I have a few sharpening tools all freehand, including Sharpmaker, DMT bench stones from XC through EF, DMT folding field sharpener, and a leather strop + paste. All the sharpening I've ever done up to the this point has been various types of v-grinds, and seems to work fairly well with the tools I have.

A skilled professional local knifemaker showed me recently the benefits of convex grinds. He was not trying to make a religion out of it, he admitted convex grinds and v-grinds both have their uses. But he said that from 40+ years of knife making and sharpening, on larger fixed blades used for heavy work, and on machetes, axes, etc., he prefers the convex grinds for both performance and edge maintainability.

This has all kinds of implications, including what kind of knives/tools I buy, and what sharpening gear and methods I use. For example, Bark River knives look well made and are interesting to me, but they are a lot of convex grinds so to maintain them, I assume I'd have to go the whole route of learning the mousepad + sandpaper approach, etc. Same thing applies to some quality axes.

I'm not trying to turn this into a convex vs v-grind debate, but as a practical matter, is it worth the hassle of buying convex-ground blades and learning to maintain convex edges if everything you have currently is v-grind and doing the job for you.

 

[FortyTwoBlades]

As a practical matter it makes little difference. Edge angle at the apex is most important, then worry about the thickness behind the edge. If you focus on those two factors the rest mostly falls into place naturally.

 

[FortyTwoBlades]

Just imagine a convex as being like an infinite number of bevels behind the edge that reduce in angle the further back you get until it's fully blended in.

 

[maximus83]

Thanks 42. So to put this in practical terms, this local knifemaker I work with, took a crappy Ludell axe with a way-too-blunt edge from the factory, re-profiled it on his belt grinder, and put a nice convex edge on it that you could shave with. And charged me $7 to do that. Pics below.

My questions are, going forward, how can I maintain this edge with the gear I have, without having to get into belt grinders and all that?

1. Would I just chuck this thing up in a vise, edge up, and work it with something like my DMT folding field sharpener (or if needed, a bastard file at first to repair major edge damage)?
2. When I do (1), won't I just be in a sense putting a micro-bevel on it at say a 20+ degree angle?

What's a little confusing is, I don't see how I'll be able to maintain that rounded convex edge on there long term without getting into belt grinders. Seems like I'd use the above approach to sharpen a number of times, but eventually, the material behind my micro-bevel gets too thick again and it's time for a re-profile from a belt grinder. Just curious what the long term approach is to maintaining my edge, if I wanted to do it all myself.

 

[Gradyw]

You can maintain a convex edge for a long time (especially on something like a bark river) with a simple strop and black compound.

I could be wrong but it looks like you have a burr on your axe.. if you look on the right side you will notice a really small line at the apex of your edge that the light is hitting... again I could be wrong but that's what it looks like

 

[adamlau]

just use your DMT plates and adjust the roll of your wrist accordingly. You'll get it down in no time

 

[FortyTwoBlades]

For touchups, natural variation in your strokes is going to produce some degree of convexity anyhow. As the edge eventually works its way back and becomes rounded and thickened, take some material off the cheeks with a file again and go back to just worrying about the edge.

 

[HeavyHanded]

Question for sharpening pros: For myself as a non-pro sharpener who has been doing all right with v-grinds, is it worth going down the road of trying to learn a 2nd type of grind (convex) and how to sharpen and maintain it well with my tools?

Background: Like many others on this forum, I have a few sharpening tools all freehand, including Sharpmaker, DMT bench stones from XC through EF, DMT folding field sharpener, and a leather strop + paste. All the sharpening I've ever done up to the this point has been various types of v-grinds, and seems to work fairly well with the tools I have.

A skilled professional local knifemaker showed me recently the benefits of convex grinds. He was not trying to make a religion out of it, he admitted convex grinds and v-grinds both have their uses. But he said that from 40+ years of knife making and sharpening, on larger fixed blades used for heavy work, and on machetes, axes, etc., he prefers the convex grinds for both performance and edge maintainability.

This has all kinds of implications, including what kind of knives/tools I buy, and what sharpening gear and methods I use. For example, Bark River knives look well made and are interesting to me, but they are a lot of convex grinds so to maintain them, I assume I'd have to go the whole route of learning the mousepad + sandpaper approach, etc. Same thing applies to some quality axes.

I'm not trying to turn this into a convex vs v-grind debate, but as a practical matter, is it worth the hassle of buying convex-ground blades and learning to maintain convex edges if everything you have currently is v-grind and doing the job for you.

Convex is actually easier in some respects. DO NOT LEARN on knives or hatchets you value! If you can do an OK job on V grind you can learn to maintain full convex.
I 100% agree with your local advice - choppers such as hatchets, machetes, etc do much better with a convex edge as long as it is ground thin.

DO NOT LEARN on sandpaper over mousepad or similar. Sandpaper is OK, but put it over the hardest surface you can manage and create the convex with mechanical wrist movements. A stone is equally applicable.

For long term maintenance, concentrate on the region just behind the edge, The actual edge will need very little work, a handful of passes, but to keep the shape you need to constantly work on keeping the overall curve of the edge.

 

[Obsessed with Edges]

An edge as shown of the axe, previously, can be maintained very, very easily with just some sandpaper (SiC wet/dry or Aluminum oxide) and a HARD backing behind it (wood, stone, glass, etc). Lay the edge flush to the paper, and scrub back & forth. That will naturally induce some convexity into the bevels behind the edge; it happens virtually automatically as your hands will rock a bit in the motion. And the hard backing will help keep the convex optimally thinner, and the edge much crisper, than is produced on a softer backing, like a mouse pad.

Once a burr's produced, I prefer to then finish with strokes in only one direction. If you're steady with your hold, that can be edge-leading on the paper (keep pressure LIGHT). If you notice it's difficult to do that without cutting or tearing the paper, then finish edge-trailing. The same motion can be used on a HARD strop (black compounds work well for these) or finer sandpaper for refinement.

I've tried using diamond hones for steels used in tools like these; but the diamond hone usually clogs very quickly with these softish steels, so you have to pause frequently to clean it up. And a painted axe head will make a gummy mess of a diamond hone as well. I've found the sandpaper method, as described above, to be the simplest way to do it.


David

 

[Chris "Anagarika"]

Murray Carter does it on a stone ... which is a flat media.

 

[maximus83]

Some great tips. GradyW, I agree that last picture does look like there's a burr on the blade, but I think that was the way the flash from my camera was bouncing off the blade, it's a great edge and no burr.

I forgot to mention in the OP, that the guy who sharpened my axe did say the same thing as others have said, that you could maintain edges like this on the stones I already or on another hard-backed medium. He also show a cool trick, he chucked up one end of one of his belts in a vise, held the other end in his hand, and did a long sweeping sharpening stroke, allowing the belt to flex slightly as he did it. He said that's how he freehand sharpens convex edges.

Chris: video was good, the diagrams plus the sharpening motions clarified it for me.

David: have you gone to using some kind of hard-backed sandpaper solution for all your sharpening? Or just for convex grinds?

 

[Obsessed with Edges]

(...)
David: have you gone to using some kind of hard-backed sandpaper solution for all your sharpening? Or just for convex grinds?

I don't use sandpaper as much for my knives anymore, just mainly because I've become more accustomed to doing everything (almost) on stones, including convexing some of my knives. BUT, I've noticed that for large, heavy & thick blades in softish steels, such as found on axes and similar tools, the large working surface area of an 8" x 11" sheet of sandpaper really speeds up the work, and lends itself better to holding the tool and scrubbing vigorously on the abrasive atop a hard surface. The steel needs nothing special in terms of the abrasive used, and sandpaper is very cheap and readily available in very coarse grits for such heavy work. Same can be said about using grinder belts in the same manner; and many of those have an added advantage of toughness and longer-term durability. I've used a 3" x 21" 150-grit zirconia-alumina belt, cut at the seam and glued flat to a board, in essentially the same manner as I've used sandpaper. It works very well, and fast.

Along similar lines of simplicity, with smaller garden-type tools like pruners and grass clippers, I often just use a 10"/12" mill bastard file for those jobs (with the tool's blade held in a vise). It seems to be the simplest for that work as well.

It sounds like you're getting some good advice and tutorial instruction from the guy who'd sharpened your axe. Sounds like he's open-minded about such things, and the use of the sanding belt as a strop (sort of barber's style) for convexing is a clever idea. I may have to try that myself.


David