Convexing Spyderco's Leaf Grind

[dzarren]

I have a habit of convexing all knives that I feel reasonable to do so to.
I'm a huge proponent of certain blade geometries, and I find myself collecting within knives that are either FFG or have some sort of convex edge, generally not scandi.

I have found that there are certain styles of initial blade geometry that are very easy to convex, or in my experience, produce good results.
The most obviously needed features are a thick blade, and a relatively short distance from spine to edge. This will of course make it a steeper wedge, and it is clear to see why it would allow itself to be convexed. Hollow grinds are out of the question, asides from forming a simple rounded secondary bevel.

Here are just a couple examples of what I do, nothing crazy, but I feel it greatly, greatly improves cutting performance in all regards. I almost refuse to cut with hollow grinds, It is just so insanely difficult by comparison to FFG, nevermind full height convex.

I don't do anything crazy, mostly i just blend the primary and secondary bevels together, and have a slight convex portion near the edge, and the rest remains FFG.

I have attached a couple examples. A Sog Blink, and a Cold steel Pocket Bushman.

AND SO MY QUESTION. How do you think spyderco's leaf grind will hold up to this process, specifically the manix 2? I feel the blade is not thick enough to start with, when considering how gradual the slope is from spine to edge. The blade in general is really thin all around.

I ask because I love my manix. It isnt like the orange ones are extremely common, and I've carried it everyday for years. I wouldnt want to affect the knife negatively, or go through with the work if the performance to effort ratio is not increased significantly. Every other knife, even hollow grinds have benefited from the process I add to the geometry, but typically have only done it to blades that are relatively "stout" in the up and down direction.

And the manix has a distal taper as well?

Thanks for reading! Here are a few pictures first of my pocket bush man and then my sog blink. The process is much more subtle on the blink, basically there I just removed the secondary edge.

I would love to gain from your experience. I should mention that edge retention is also much much better, and it seems to get much sharper, and of course, convex edges are the easiest edges to maintain.

 

[Jason B.]

In truth all you are doing is making a smooth and very obtuse bevel. Likely reducing the performance of your knives by a great deal. You would be better off using stones because your apex would be crisper and sharper plus, hand sharpening has its degrees of convexiy and is typically enough for already thinly ground blades.

To compensate you could convex further up the blade reducing the whole convex geometry but you will run into problems doing that on already thin blades.

 

[Obsessed with Edges]

I'd generally agree with Jason's comments on this. Convexing the existing factory edge will likely just make the edge angle wider than it already is, effectively negating any benefit from the rounded/smoothed shoulders. I started out trying to convex factory edges this way, and was never happy with the results afterward; the cutting geometry at the apex always suffered for it (rounder/wider/blunter).

Having experienced that disappointment, I've since taken a different approach by ALWAYS first thinning the edge geometry to something pretty low, maybe 25-30° inclusive, leaving a very crisp & fully-apexed V-bevelled edge. I've preferred using a guided setup to do this, to ensure the V-bevels are as crisp as possible. Only then will I gradually round/smooth out the shoulders of that new, thinner edge, making every effort to avoid altering the apex itself, or getting too close to it with the convex. Just taking the hard 'corners' off the shoulders will improve cutting, especially if the edge geometry is already fairly acute.

I will say though, my Manix2 in S90V is one of the few knives I haven't altered at all, as it's grind & edge geometry are already excellent from the factory. It's a laser-beam slicer, so I haven't felt any need to 'fix' that. If yours is anything like the one I've got, just make absolutely sure you really want to change it, before doing so.

And if convexing S30V (assuming so, for the Manix2) on sandpaper with a softish backing, I've never liked trying to shape S30V that way. Between the steel's vanadium carbides (harder than the abrasive used), and the soft backing under the sandpaper, S30V won't attain the crispness at the apex like it would on a hard hone. If convexing it at all, I'd use a diamond hone for that.


David

 

[Jason B.]

That's a very good approach David, I do the same when Convexing. Sandpaper wears quickly so I get as much work done on the stones as possible, saves time and effort.

 

[Obsessed with Edges]

That's a very good approach David, I do the same when Convexing. Sandpaper wears quickly so I get as much work done on the stones as possible, saves time and effort.

Thanks Jason. :thumbup:

I've edited my earlier reply to add my thoughts about using sandpaper on S30V. Agree, it wears very fast, and I haven't been as happy with results on S30V (assumed for the Manix2), especially if used on a softish backing for convexing; just not aggressive enough on that steel.


David