Blade and edge design and curly wood shavings?

[pinnah]

Why is it that some knives more easily make nice curling wood shavings while others do not? Grind? Edge profile? Blade shape? Handle? Steel? Blade thickness?

I ask because I was totally surprised this morning when I was making some feather sticks to start a fire. A knife I had written off over the past few years (my Buck 110) totally surprised.

[David Martin: you can say "I told you so." ]

I recognize that my technique has a lot to do with it. And that I'm not same person today that I was 1 or 2 years ago.


This morning's fire making prompted me to dig out several knives and to make some feather sticks side by each. Here they are in reverse order of effectiveness.

Opinel #9 (and 10) - Flat convex grind. 12C27. They tended to either skip or dive. Perhaps the round handle makes them hard to control but I don't think that's the main issue. At the end of the stroke, they tended to pop the shavings off the stick.

Buck 500 - hollow grind. 440C. The handle is just too small for my XL hands to control when applying firm consistent pressure for the cuts. No way to really get a feel for the blade as the knife just moved around in my hand too much.

Schrade 51OT - Flat grind. 440A. This felt similar to the Opinels, either skipping or diving. The wide flat handle gave better edge angle control. Still, it had the tendency to roll out and pop off the shavings at the end of the stroke.

Schrade-Walden H-15 - convexed sabre grind. 1095. This knife made longer curling shavings with greater ease. STill a bit tricky to control at the end of the cut. I wonder if the issue is the thinness of the blade and the higher position of the shoulder - sort of on the spectrum towards full flat.

Buck 110 - Hollow grind. 440C. This is a 2 dot version that has a swell of thickness just above the edge. It gave great control of the edge angle and consistently ripped off perfect curls.

Mora Companion HD - Modified convexed scandi. 1095. The handle is by far the easiest to control. Unmodified, this knife dove deep into wood and didn't make curled shavings well. With the shoulder convexed and a 20-dps micobevel, it is the best that I have, but not by whole lot compared to, surprisingly to me, my old Buck 110.


Not listed here are several more recent Bucks and a Case both with 420HC and thinner hollow grinds. They were bad enough at this that I've gotten rid of them.

I'm wondering if the thickness of the old 2 dot 110 behind the edge is a factor here.

Thoughts and insights?

 

[Obsessed with Edges]

I'm inclined to believe that the held angle and edge geometry (not primary or overall geometry above the edge) make more difference. I say this, because I've noticed in particular how easily a chisel edge works in such things. If you compare to true woodworking tools, like chisels and planes, both of which are very good at getting those thin 'curls' of shavings, it starts to make sense. I'd never really given it much thought, until I'd been messing around cutting paper with my Leatherman Micra's blade (chisel grind), and noticed how easily the flat back of the chisel grind 'steers' the cut in a perfectly straight path. If done at the very edge of a piece of paper, at a very low angle, the curls coming off the edge of the paper are very easy to control, and can be made very, very thin. I suspect this is why a Scandi grind is so well-reputed for these things, as the very wide & flat bevels should make the blade very stable in the cut, avoiding the ups/downs of other edge profiles that would be more likely to plunge/dive, or rise up and break off the shavings early in the cut.


David

 

[pinnah]

David, the plane analogy is helpful.

What explains the good performance of the 2 dot Buck 110. Remember, they have a noticeable swell above the edge. Could this be providing the fulcrum to control the cutting angle?

 

[Obsessed with Edges]

David, the plane analogy is helpful.

What explains the good performance of the 2 dot Buck 110. Remember, they have a noticeable swell above the edge. Could this be providing the fulcrum to control the cutting angle?

Just a hunch, but the Buck's main advantage may just be in the beefy handle. I've always liked how much control is afforded with a 'fist-full' grip of handle on a knife, and the Bucks have always excelled at that. If the steadiness of held angle is important in getting those thin curls going, then I could see how the Buck's handle could control it more easily; even more so in the relative squareness of the Buck handles in cross-section (especially in the older ones, like the 2-dot you have). By contrast, you mentioned the roundness of Opinel's handles, and how it may make controlling angle more difficult; I've noticed the same tendency in sharpening my Opinels, as the round handle seems to contribute to pitching/rolling of the angle during sharpening. I've also noticed this with much smaller knives, where the handle is very small in cross-section, and it's difficult to control in larger hands.


David

 

[pinnah]

Nod. Something more is going on with the 2 dot 110. The Schrade 51OT is the best in terms of blade angle control second only to the Companion. But the 51OT skips off much more easily. The Bucks blade sort of "hooks up" much like the Mora. Hrmmm

 

[Obsessed with Edges]

David, the plane analogy is helpful.

What explains the good performance of the 2 dot Buck 110. Remember, they have a noticeable swell above the edge. Could this be providing the fulcrum to control the cutting angle?

Another thought (speculation?); may or may not be pertinent, depending on how the blade is actually held and used during the cut:

(I'm looking at my 2-dot 112 now, to see if this makes sense in how I'm picturing things)
The held angle might be more stabilized if each side of the 'hollow' in the Buck blade is in contact during the cut. In other words, if the shoulder above the hollow is riding on the wood, while the shoulder of the edge grind (below the hollow) is also in contact, I'd think the held angle of the edge should be a lot more stable. Depending on the angle of the edge grind itself, and how that angle relates to the angle at which the blade is riding in the wood, that might impact the consistency of the shavings produced. Compare to the narrow convex of the Opinel, of which there can really only be one point of contact on the blade's grind above the edge, at the apex of the convex (near middle of the blade's cross-section). I could see how that convex might tend to make the blade pitch forward (edge diving) or backward (edge lifting) during the cut.

Again, more speculation. But maybe something's there...


David

 

[HeavyHanded]

Interesting discussion. There could very well be an ideal primary/secondary grind combo for different types of wood if one delved deep enough. I find my thin edges do the best - full convex with acute terminal apex, or Scandi grind at 25* inclusive (or less). Having an acute apex that allows good bite, yet a bit of swell behind it to take over once the edge cuts in seems to be key. Also, more refined is better but cannot overcome poor overall geometry.

 

[pinnah]

David,

Owing to how making feather sticks shaves off material, the Buck 110 very definitely did NOT have the top of the hollow on the wood. What ever is happening is happening closer to the edge.

Martin,

All of the knives are within some delta of 20-dps with a 17-dps secondary bevel.

I'm wondering if the issue isn't just the fact that there's a back bevel but how long that back bevel angle is sustained by the material above the edge.

The Mora Companion is roughly 17-dps all the way back along the scandi grind. It gets the thickest fastest and when laid up against the wood, has the largest supporting fulcrum (David's good point about chisels). I think the Buck is the the next thickest above the edge, owing to that unique flare in the edge before the hollow kicks in. It's like a fat convex on the bottom with a hollow grind above.

[As an aside, I lived in Henrietta when I was a young pup. That was a longggggg time ago.]

Thanks for indulging me guys. Complex dynamical systems offer no end of entertainment.

 

[HeavyHanded]

The wedging action from one to the next is certainly a function of the apex and contact points going back. You're probably spot on the shape of the Buck 110.

I lived in Henrietta too for a year or so before moving down to Fla, that was back in 86-87...

 

[AreBeeBee]

My experience, looking back now 50+ years on Scout days, is that the wood you're working on plays a big role as well.

Some woods just never peeled off curls very well, while another stick/branch picked up in the woods yielded decent fire-starting materials. As I was using my Imperial scout/camper knife (with amateurish sharpening) for all this, the only real variable in the deal was the stick of wood, which was random pick-of-the-forest-floor near the fire or camp site.