Convex edge working sweet

[hawkinsa21]

Hi guys,

I short while ago, I posted a pic of my FBM with a tiny ding in it, and Jerry blessed the thread re-assuring me that it wasn't a chip... (what was I thinking??)

Anyhow, I decided to give the convex edge treatment with sandpaper a go, and see how easy it was, and what all the hype was about...


Firstly, only ever having used an old whetstone and a steel to sharpen penknives and small folders, taking SANDPAPER to a £240 knife (what it cost me including shipping etc) was a very scary thought, but I got stuck right in...


INFI is SO forgiving when sharpening like this, and with only 30 minutes of effort, I had a fairly decent convex edge, and managed to get the edge fairly shiny with just 600 grit paper and a strop on an old leather belt (anything above 800 grit is hard to get here).


The knife chops like a champ, and is much sharper than before... I will try to get some pics posted up, and also that little ding is almost invisible now... Jerry was right in the fact that it sharpened right out...


The main reason for starting this topic was that if anyone has ever considered creating a convex edge, but is too scared to take the sandpaper to the INFI, dont be! Its so easy to do, and any mistakes can be corrected easily. It doesn't take ages, and the edge you get at the end is much more effective than the factory edge... and after heavy chopping at the weekend, still shows no signs of wear



Question:

How extreme an angle can you get with convex before you start risking making the edge weak??

My convex edge mainly takes away the secondary bevel (I think thats correct) and rounds off the V shaped edge so the whole thing has a distinct curve... but I know that with more time and effort, you can bring the curve back a lot more...



PS - I then got convex fever and resharpend my father's axe's as well


For those that aren't sure what a convex edge is, its like an axe grind (sometimes called that), and its where the sides of the steel kind of 'curve' into the edge, rather than having visible bevels...


:thumbup:


Alex

 

[idahoskunk]

sounds cool, post some pics please.




.

 

[mikeymoto]

And maybe describe how you did it with sandpaper for those who may not know how!

 

[hawkinsa21]

Skunk - OK, I'll get some done when I get home from work...

mikey - I had though about doing that... I had read some tutorials and they didn't explain any techniques, but I think JAB helped get my head around it!


Alex

 

[Ironballs]

glad she is 130% fixed.

angle questions- i have often herd to elevate the spine off the sand paper about the width of the spine or 2x it...

and if i am typing funny now, its because i took about 3/16" off the tip of my pinky with a convexed blade last night (a CS scimitar i had stropped the night before). At a restaurant, cutting up my daughters food, no prob.. then cleaning the blade i was careless. Felt like a nothing papercut, but was clean from pad to nail. I quickly flopped on the flesh, pressed it back on and squeezed tight under a napkin to finish dinner... then crossed the street to buy some crazy glue... and glued around the edges- all done- Krazy glue makes for great stiches/instant bond. Pinch the wound closed and drip it on the outside (ok to let it penetrate just a little bit, but not too much inside the wound or it would heal). may need to touch up ever 2-3 days until healed. Just 4 hours later i had color back in the tip of the pinky. ode to the convex edge

 

[mikeymoto]

Sounds like we need to start a "tell us how you sliced yourself with your scary sharp INFI" thread. I've got a nice scar on my right thumb from being a jackass and cord wrapping a skelly warden...without the blade covered....and having a little slip-up. It's not convexed, but still pretty dang sharp. Like Ironballs I had a flap that I pressed down, covered it up, and it survived albeit with a moon-shaped scar around the edge of the slice. Doh!!

If I were a knife-smith I wouldn't have any fingers left in no time flat.

 

[kbuzbee]

Nicely done!

As you've probably guessed, the angle you "can" take a convex edge is pretty thin (depending on it's intended use) but, regardless, a convex edge will always be stronger than a V. There is more metal behind it. So convex away!

Ken

 

[hawkinsa21]

glad she is 130% fixed.

angle questions- i have often herd to elevate the spine off the sand paper about the width of the spine or 2x it...

and if i am typing funny now, its because i took about 3/16" off the tip of my pinky with a convexed blade last night (a CS scimitar i had stropped the night before). At a restaurant, cutting up my daughters food, no prob.. then cleaning the blade i was careless. Felt like a nothing papercut, but was clean from pad to nail. I quickly flopped on the flesh, pressed it back on and squeezed tight under a napkin to finish dinner... then crossed the street to buy some crazy glue... and glued around the edges- all done- Krazy glue makes for great stiches/instant bond. Pinch the wound closed and drip it on the outside (ok to let it penetrate just a little bit, but not too much inside the wound or it would heal). may need to touch up ever 2-3 days until healed. Just 4 hours later i had color back in the tip of the pinky. ode to the convex edge

Ouch!!! Now that sucks!! Great job on the quick fix though, nice one :thumbup:


I started raised about 1cm off of the sandpaper, on 220 grit... just dragged. As JAB said to me, you will naturally elevate the blade as you pull it back near the end of the drag, therefor creating the curved effect... spend about 10 minutes on both sides at 220, then 5 minutes each side on 600 followed by a stropping for about 15 minutes... bites nicely as well... One day I'll write a thread on convexing from a fresh, once I get a new piece of INFI...

I don't have a good enough camera to get really close up and have crisp pictures...


I expect when I have a spare 2 or 3 hours, I'll convex it even thinner... it can take it... I need to work on my stropping technique though.. it could do with getting better, mind you working on the thickness of the FBM, I'd need to thin it a fair bit to get it really razor sharp!