Anyone doing convex grinds?

Smallshop

KNIFE MAKER
I am a fan of Bark River Knives. I think they are a great production knife that still looks/feels custom....I found one in a Pawn Shop that I go in and look at (well...i did before it got sold) and I love the look and feel of the convex...super sharp and the thing looks strong. 30K guys raving about them on the BRK forum can't be too far wrong...lol. That company is amazing with what they produce...and most of 'em with a convex grind.

The short Bowie I am working on will be a convex. I have been practicing grinding convex and of course it feels different. I seem to get the best results slacking the belt a bit...running it fast...and grinding up top where there is space between the wheels. It definitely feels more "artsy" than science.... I am working on the KITH Bowie for Gene Kimmi...He gave me a real beauty so of course I want to reciprocate....lol.

Any grinding tips or pros and cons of convex blades would be appreciated!
 

J. Doyle

Dealer - Purveyor
I think many custom makers (including me) utilize a convex edge. The amount of convex depends on the size/type of knife and intended use/edge thickness.

I am VERY familiar with bark river knives and their process and methodology.

In my opinion, I'm a big fan of the convex edge for a few reasons (I'll save that for another thread) but the reasons to fully convex grind an entire blade seems unnecessary to me. I know the claims but any performance gain over a flat ground blade with convex edge would be negligible at very best.

I have my own theory on why blades are fully convex ground there (I've been in their shop while they worked many times) but again I'll save that for another discussion.

This is just my opinion from my personal experiences.
 

Chris Railey

KNIFE MAKER
I do convex edges on everything except my Scandi-grinds. I have never done a full convex grind. The appeal may be more aesthetic now a days because it is different. Just like the Hamon (well, differential HT) many years ago was functional but now due to advances in steel and HT techniques it is mainly an aesthetic addition. It really does not matter though. I would like to see pictures when you are done please I am not sure I have ever used a knife with a convex grind.
 

Andre Grobler

Well-Known Member
I use convex grinds for kitchen knives and competition cutters, because food release and edge stability... and what you want to achieve varies a lot... So in order to not be bound by how fast the grinder runs, what grit how hard the belt backing, and how tight the belt tension is, i put in a flatgrind at two to three angles, angled just by eye... Just until i am almost apexed and it looks like i want, and even all sides, then i start blending the bevels on a slack, but well tensioned belt. If i feel there is too sharp a kick in the geometry, i take it back to platen to remove metal more accurately, if i am dealing with a thick piece of metal for competition cutters, i use a wheel to hog steel faster and cooler than the platen. I usually just lightly blend on 60 grit, then do the final blend on 80 or 120grit. It is hard to hand finish these blades though, as there are very little flat areas on the blade, so you sand and sand for a while before things look better... it is very easy to grind dips in the blade...
 

Smallshop

KNIFE MAKER
Guys...anything I add here on technique is somewhat questionable as I am new to this style of blade....I think it is unnecessary to convex an entire blade width. I am doing it for one main reason (though I do like the aesthetics of it). The reason is: (for me) it is much easier to visualise the convex and keep it consistent on the grinder the farther up the blade it goes.

you still are doing most of your grinding down near the edge. The first grinds I did would not cut due to too much convex and too much drop at the edge. The convex has to be pretty subtle for it to slice or you have just created a horizontal hatchet...lol!

I would love to hear your discoveries on this type of blade, John Doyle. And anyone else...!

Things being shared have already confirmed some of my thinking...which is sure helpful.

Thanks guys! (Questions, theories, and observations welcome!)
 

Smallshop

KNIFE MAKER
Another thing I notice is keeping my corner radius in the plunge line crisp/small also makes it easier to see how the convex is shaping up...

of course the right side is always easier for me to do than the left....sigh
 

Smallshop

KNIFE MAKER
I think most of us are...

As soon as the handle is in my left hand...things get ugly...

So glad to be back in the shop though....had my doubts there for a while...
 

Smallshop

KNIFE MAKER
Thanks Bruce!
Most of 2019 I didn't do any making...had to do machining to keep from bankruptcy...and physically felt terrible...I have more energy right now than I did all of 2019!

I do owe some knives to folks and am catching up...still have some bad days but less and less....lockdown has kept my nose to the grindstone...lol!
 

Smallshop

KNIFE MAKER
Personally I flat grind for weight reduction, then convex edges for less drag when cutting and edge durability.
How thick do you leave the edge on the flat grind to begin the convex....and how far up the blade do you go with the convex....(trying to get a feel for what you and J. Doyle are describing...)
Thanks Ed...
 

Smallshop

KNIFE MAKER
IF you want to do convex grinds..... nothing better then......

View attachment 73864
Personally I flat grind for weight reduction, then convex edges for less drag when cutting and edge durability.
Looks like exactly what I need....would keep me from running the belt off the spools AND allow me to get a tighter convex without over-slacking the belt...or so it looks to me.

John D...would you know if Mike Stewart's guys use these?
 

J. Doyle

Dealer - Purveyor
Thickness of edge before convexing depends on knife size/type, intended use and possibly to some degree steel type and heat treatment. Same applies to how high up the convex goes, but for me I typically take it up 1/8" to 3/8" depending on knife type and use.

As far as I know, bark river uses burr king grinders exclusively and grinds on a slack belt with nothing nearly as complex as rotary platens. I doubt any of that has changed, though admittedly I have not been there in several years now.
 
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