Convex grind on traditionals?

A

adoboyo

Joined
Aug 20, 2012
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Hi guys, recently got my SFO HJ and love it. I sharpened it today with some Shapton glass stones and it cuts phone book paper now. I've read about a convex grind and it sounds like something I want do put on this guy. I ordered a backup from KSF and also ordered their Sharpening kit for the hell of it.

My question is, should I put a convex grind on this and my other traditionals? Is it the best grind for these type of knives? Also, since my Harness Jack is newly sharpened, should I start at the lowest grit and move up through every grit? Or what is a good grit pattern to go through if this guy didn't have a convex edge to start with?

Thanks!
 
Hi adoboyo

A nice aspect to sharpening is everyone has their own methods:)

I reprofile all my knives with a convex edge bevel using the mouse mat method (plenty on this if you do a search). For reprofiling I start with 600 grit, decide an angle and work both sides evenly until I have reached the edge (no light will reflect along the entire edge or a burr has formed). Then about 10 strokes on each side with 800 & 1000. I follow that with approx 10 strokes on a leather strop (this can vary considerably depending on steel, maybe 20 for CPM 154).

One thing to consider is if you reprofile an edge like this you will get scratches on the blade. No worries on a user, particularly with 1095 as a patina hides all sins. I brush finish my custom' once done.

As with everything, practice makes perfect. Enjoy:)

Feel free to PM me if you need more detail.

Sam
 
Thank you very much Sam! Now when you say when light doesn't reflect..now I'm sure I'm over thinking it, but does that mean the whole edge or the cutting edge doesn't reflect light? Pretty much, when it isn't necessarily shiny anymore correct?

Also, will putting different grinds on the blade negatively effect it in any way? Like going to a convex from a scandi grind?
 
This is tricky to explain:)

When you start to reprofile the first part of the blade you will wear is the shoulder where the manufacturers edge bevel meets the main blade grind. You will want to continue until you reach the very edge. You can check this by holding the blade up to the light, any original edge left will reflect light differently to the edge you are creating. You're aiming for a new, clean edge so that when you sharpen the edge you hit it all.

Yes, there are risks much like any sharpening method. Generally, with anything from an axe to a scalpel you are trying to find a balance between cutting performance, material being cut and blade preservation. If you over thin then you risk chipping or edge rolling when cutting harder material. The mousemat method is far from a precise science, I wouldn't practice on your favourite knife. I've messed up a couple of knives over the years by over thinning the edge. Even then it's not the end of the world as you can steepen your profile and put a micro bevel on. One nice thing about traditionals is the blades aren't wide from spine to edge , so lend themselves well to this method.
 
I have it on one knife, a First Gen Trail Master. Super edge holding but I like being able to touch up blades with minimal fuss in the field with a pocket stone, rod or steel...can't do that very well with the Trail Master so I probably won't be buying anymore Convex grind knives.
 
I think Maintenance, Tinkering & Embellishment is a good place for this one.
 
Most of my traditional knives end up with convex grinds on them, as I prefer to fine-tune and maintain them using a trailing-edge (stropping) technique on sandpaper and hard strops with compound. Since most traditionals feature relatively simple & minimally wear-resistant blade steels, it doesn't take long at all to work a nice, acute V-bevel (applied with something like a Fine diamond hone, from the start) into a nice & acute convex*. Even a hard-backed strop with some fairly aggressive compound will do it pretty quickly, on these blades. So long as technique is good (steady angle held, good use of pressure), the cutting edge itself will still cut like a laser beam, and the convexed shoulders behind the edge will make slicing into thicker material a slick experience.

( * = I would recommend starting with a fairly acute V-bevel before convexing, as the process will usually result in an edge angle that's a little wider, when finished. )

Edited to add:
A typical sequence I've settled into, for traditional blades, is re-bevelling to 30° inclusive or lower with a Coarse/Fine diamond hone (edge-leading or scrubbing technique), following with trailing-edge technique on 320-grit sandpaper affixed to some hard plywood (this gets the convex applied quickly), then following by stropping on firm paper over plywood (again, firmly affixed) with some white compound (2-5 micron). The compound on the paper-over-plywood strop will quickly get the polish going, and does a wonderful job cleaning up any burrs left by the sandpaper. Beyond this, I'll maintain these edges mostly on the paper-over-plywood strop (I also use some linen from an old shirt, in the same fashion) with the 2-5 micron white compound.


David
 
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