Does grind mean everything?

[addyb]

Here's a thought:

For years, my old Victorinox SAK has had it's place in my pocket. I remember at a young age (7 or 8) my Grandfather was driving through a parking lot to go to the grocery store. He stopped the car suddenly, walked out, and picked up the SAK that I still have to this day. I've had new cellidor handles added to it, but everytime I use it the memory of him is with me.

Anyway, enough of the sob story! For a while I couldn't quite figure out why my SAK would dull so quickly. The steel's actually not so bad, at 56hrc, it's easy to sharpen, and while it isn't incredibly hard, there are much softer steels out there, as I'm sure most of you would agree.

I ended up checking out the "Secret Order of Swiss Army Knives" and read the page about convex grinds. For years I used to sharpen my SAK on an arkansas stone set, strop it to a razor, and have it dull within a day. After reading the convex page, I setup an old mousepad, some wet/dry paper, and followed the directions.

The point is, after slightly convex-ing the bevel on the knife, it's edge retention has gone WAY up, and I haven't sharpened it in weeks.

So, is the grind of the steel the most important aspect? Or is hardness? Or blade shape? Or a combination of everything? I know that there is no perfect steel, but in what order would you put steel's aspects?

A.

 

[Stew]

Well, this one's going to be interesing!

I think you may get a few different opinions.

 

[OldJimbo]

In a word:
Yes.

 

[richardw]

I to am a member of SOSAK and have studied this article with interest.

I have not had ago yet but, given the level of enthusiasm on SOSAK, feel I must give it a try.

I too would be interested in any positive/negative comments.

Richard

 

[Andy]

I like convex grinds on a SAK but I haven't found it makes a huge difference to how long the edge lasts. Maybe you were getting a wire edge before and that's why it didn't last long.

 

[troyka]

what is the Secret Order of Swiss Army Knives

dont say its a secret....

 

[cgait]

what do you mean wire edge?

 

[leon-1]

what do you mean wire edge?

You get an area on the edge that is very thin, so instead of the edge angle being a constant the last half mm of the angle is the same thickness.

This can cause the edge to roll, it can also cause the fine wire (the area that is the same thickness) to seperate from the rest of the bevel leaving an area that is considerably wider (hence blunter) than the edge itself.

Some steels seem to be more prone to this than others, but if the edge angle is shallow you are more likely to suffer from this, hence if you slightly convex the edge you have a steeper edge geometry that will last longer and is less prone to damage.

I hope this makes some sense

 

[redcollective]

what do you mean wire edge?

A microscopic sliver of metal that you should remove with stropping? From what I've read it easily folds, increasing the speed with which the blade appears to dull. Someone else mat be able to confirm this, but I'm sure I've seen some highly magnified pictures of a blade edge on a woodwork site somewhere which illustrate this - buggered if I can remember where now..... anyone?

 

[Stew]

I've seen some highly magnified pictures of a blade edge on a woodwork site somewhere which illustrate this - buggered if I can remember where now..... anyone?

 

[Hoodoo]

I'm not disputing your results but I usually find that convexing a secondary bevel on a flat ground knife weakens the edge. You are actually removing metal from the edge, which would actually weaken it, although it will improve slicing ability considerably.

When ALL THINGS ARE EQUAL, it makes sense that the convex edge/grind will be stronger. But when you convex a flat or hollow ground knife with a secondary bevel, all things ARE NOT EQUAL. If all you are doing is knocking off the shoulder of the secondary bevel, the end result is to thin the edge. How that makes it stronger is beyond me. If however, you change the overall angle of the secondary bevel, then you might be able to make a case for increased strength.

 

[mojofilter]

I'm not disputing your results but I usually find that convexing a secondary bevel on a flat ground knife weakens the edge. You are actually removing metal from the edge, which would actually weaken it, although it will improve slicing ability considerably.

When ALL THINGS ARE EQUAL, it makes sense that the convex edge/grind will be stronger. But when you convex a flat or hollow ground knife with a secondary bevel, all things ARE NOT EQUAL. If all you are doing is knocking off the shoulder of the secondary bevel, the end result is to thin the edge. How that makes it stronger is beyond me. If however, you change the overall angle of the secondary bevel, then you might be able to make a case for increased strength.

I agree with what you are saying at the shoulder of the bevel being thinned and thus weakened, but surely the act of convexing has made the ultimate edge angle slightly steeper and stronger.

I am struggling to put what I'm thinking into words

 

[Hoodoo]

mojo, it really depends on how you convexed the edge. If you used a mousepad and sandpaper, you likely steepened the angle at the edge. If you use a flat stone, you can easily convex down to the edge without affecting the angle. Lots of whittlers do this because they want a nice, thin edge but a little bevel will allow you to make curls more easily.

 

[cgait]

i understand what your talking about now i have heard of it as something else sorry . I think i've heard of it as being called a burr. Forgive my spelling aswell. But i do know what you on about

 

[addyb]

Well, to be honest, I didn't actually take a whole lot of metal off the edge on my SAK. Just enough to give the bevel a slight convex. At this point in time, it is not so sharp that I can take hairs off my arm (that dulled very quickly, even though I always removed the wire bead) but it slices well, and so far, the edge retention has improved considerably. So, I'm quite happy with my results. I didn't just rush into convex-ing my SAK, I used an old Barlow that I had lying around to train myself. Eventually I moved to my SAK, and I think I've got it down pat now. Next trip I do, I'm going to slice up a mousepad into a square, and put it with some wet/dry paper into a ziploc bag incase I need to do field sharpening.

A.

 

[OldJimbo]

In a lot of cases even heavy duty grinding to fully convex a Mora - doesn't change the thickness of the blade just behind the edge. But I have two machetes which simply wouldn't hold up against the devil's club and hardhack here. The edges would look like saws in very short order. Then I'd file back the V secondary bevels and hone smooth. On advice I ground back the bevels putting on a convex going back more than 1". The edges have held up vastly better - probably by a factor of ten - despite being much thinner.
We never have come up with an explanation!

 

[Andy]

I was talking about this with a material science mate of mine. All we could think of what that since it passes through the material a bit easier it wont deflex as much.

 

[OldJimbo]

We've had all sorts of ideas - but never anything that's stood out as the obvious answer.

 

[ChrisKavanaugh]

Pick up an ancient achuelian hand axe and you have a convex body with hollow concoidal fractures. Our primal ancestors had the same happy problem in the beginning of things. The hand axes got dull and had to be rechipped. I say happy, because a convex/Moran, sabre/scandinavian or hollowground knife in plain vanilla old 1065 carbon steel with a penchant for going dull at day's end is just fine with me. It got dull splitting firewood, constructing my shelter, filleting the fish caught with the 3 pronged spear I carved and makes the scary rustling of a mouse seem more like a raccoon instead of a lion. Few of us are prime of youth, robust manly men and ladys. We get a little tired at the end of the day. So out comes the billy and maybe a few aspirin. It's called maintenance. Your fast dulling SAK always beats your teeth

 

[addyb]

Oh yes, I know that a knife dulling is inevitable. It's like death. You can fight it all you want, but eventually it will happen.

The reason I posted this thread was to try and gather other people's opinions on blade aspects, what works, and what doesn't.

You see, when I read about convex grinds and how they relate to slicing (cutting) I was curious, and wanted to see how I could improve my SAK. Just curiosity, that's all it was.

Well, after giving the knife a slight convex bevel, the edge retention has improved considerably. Of course, the knife is not quite able to nick hairs off my arm, but it's a trade off. It's still very sharp, but due to the bevel, the knife is able to stay sharp far longer.

Mind you, if I were to stop my razor blades to a convex, well, chances are I wouldn't have much luck shaving with them. But I'd probably never have to change a blade again!

That's my $0.02 cents. Thanks guys!

A.