Slipjoint cutting contest

fasteddie

fasteddie

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Feb 22, 2002
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Went to vist Jerry Halfrich in San Marcos TX today. For those of you who don't know Jerry, he's a hunter and guide who's been making hunters, lockbacks, and liner locks for many years. All his stuff is field tested and are serious cuttng tools. Recently, Jerry has turned his attention to slipjoints. And with some help from Tony Bose and Bill Ruple, he's turned out a dozen or so small single blade trappers that are very well made. And because of his background and experience, they are serious cutting tools. (I've seen Jerry actually split a hair with a hunting knife.) Now he's trying his hand at the Bose backpocket knife... 4.5 inches closed. So anyway, I'm in his shop looking at his first two backpocket knives, and he starts explaining hollow grinding with a constant taper. He says that a lot of makers who hollow grind dont get it quite right... the blades actually go in and then go back out causing a fat edge.

So he grabs three knives and takes me out in his yard, and lops the limb off a box elder tree and proceeds to slice through a 3/4 inch diameter, wet, green branch with one stroke of his backpocket knife. He then takes another famous makers knife and does the same thing and the knife binds up and wont go more than 1/3 of the way through the branch. Then, we take my Tony Bose backpocket knife in A-2 steel, maybe 10 years old, and it goes through the limb in one stroke as well. He handed me a branch and the knives and I redo the tests myself. Same result. The slipjoints slice right thru, the other knife binds up.

So Jerry repeats... the knife has to be a constant taper to cut well. Any knife can shave hair, but the geometry has to be just right to cut through wood Think about it. The blade behind the edge acts as wedge to keep the wood apart so that the edge can keep cutting. Makes sense.

Oh, and Jerry is really getting the hang of slipjoints. Watch out, he's going places. Do you have a folding pocket knife that will split a hair AND cut a 3/4 inch branch in one stroke?
Jerry cutting the limb:
halfrichcuttingbranch.jpg


Jerry's knife and branch:
halfrichcutter.jpg


Tony's knife and branch:
tonybosecutterw.jpg
 
Hey Ed
Nice Post..I Have a couple now From Jerry a Shadow and a lockback Remington guide...They are two of the sharpest knives I own..I havent had them long enough to see how tough the edge is but based on your description and also having spoken with Jerry Im sure they will perform beyond expectations

Now How was his Backpocket?
 
Those are very nice looking knives in your hand there.

3/4 inch green wet limb in one cut? Not as hard as you think, green wood cuts easy. This is when the wood will be at its easiest to cut. And it looks like he used a shallow enough angle to take at least twice the thickness. Any well sharpened larger bladed knife like a sodbuster or Daddy barlow or large trapper will do that if you have it sharpened right. At that point its just as important to have a good sized handle to push with. But he's right, it has to be made with a slight taper and ground thin. Alot of modern knives are not made this way, their stamped out blades with high angle dubbed on edge not being too sharp. A knife magazine tactical will never do it! Hollow grinding is good for a thin sharp edge, but at the cost of not leaving as much steel right in back of the edge for strength. One of the major things about a hollow grind is that it's easy to do if you have a small diameter wheel on your grinder. A harder knife to make by hand is the convex blade, like the Opinel, or a long flat grind like on a large Eye-brand sodbuster. What is interesting to see is take an open Opinel, and lay a small ruler or other strait edge across the blade from spine to edge.

I've made very similar cuts with my larger sodbusters and number nine Opinel when gathering sapplings for the hiking staves I made for all the family one Christmas.

But if you set that branch aside for a couple of months in a cool dark basement to dry and start to age, you have a way different story. Box elder is not that hard a wood, but try that with hornbeam or white oak or shag bark hickory.

The other famous makers knife only went 1/3 of the way and bound up? It had to be dull not to go even half way in soft green wood, or really profiled very thick.
 
jackknife said:
Those are very nice looking knives in your hand there.

3/4 inch green wet limb in one cut? Not as hard as you think, green wood cuts easy. This is when the wood will be at its easiest to cut. And it looks like he used a shallow enough angle to take at least twice the thickness. Any well sharpened larger bladed knife like a sodbuster or Daddy barlow or large trapper will do that if you have it sharpened right. At that point its just as important to have a good sized handle to push with. But he's right, it has to be made with a slight taper and ground thin. Alot of modern knives are not made this way, their stamped out blades with high angle dubbed on edge not being too sharp. A knife magazine tactical will never do it! Hollow grinding is good for a thin sharp edge, but at the cost of not leaving as much steel right in back of the edge for strength. One of the major things about a hollow grind is that it's easy to do if you have a small diameter wheel on your grinder. A harder knife to make by hand is the convex blade, like the Opinel, or a long flat grind like on a large Eye-brand sodbuster. What is interesting to see is take an open Opinel, and lay a small ruler or other strait edge across the blade from spine to edge.

I've made very similar cuts with my larger sodbusters and number nine Opinel when gathering sapplings for the hiking staves I made for all the family one Christmas.

But if you set that branch aside for a couple of months in a cool dark basement to dry and start to age, you have a way different story. Box elder is not that hard a wood, but try that with hornbeam or white oak or shag bark hickory.

The other famous makers knife only went 1/3 of the way and bound up? It had to be dull not to go even half way in soft green wood, or really profiled very thick.
Click to expand...

You're off on a few things here. Agreed that green wood is softer and easier to cut. These weren't huge knifes. Didn't measure, but I think the blades on the slipjoints measured 3.25. I would guess that there are as many knives that would flunk this test as pass it. Even with a sharp edge. We didn't even sharpen the back pocket knives before the test. Just pulled them out and started cutting. And did this test over and over.

Hollow grinding might be easy to do, but not that easy to do right. And the smaller the wheel, the harder it is to get right. Look at the math for a minute. The larger the wheel, the more that arc approaches a straight line, like you'd get on a flat grind. But it has the advantage of the flat in that you can keep a more parallel taper as you approach the edge giving a blade that will stay a relatively thin thru the life of that knife. Jerry's knife here was done on a 10. He's now using a 14 inch wheel like the Boses use. A lot of manufacturers use wheels up to several feet in diameter. I've heard of wheels up to 6 feet in diameter used for production knife grinding.

I won't say much about the other makers knife that only went a third of the way through, but it was a big straight knife, very sharp by any other test, large handle and a very modern steel. It cut paper and popped hair just fine. The only difference was the shape of the hollow grind. A properly done hollow grind doesnt have to be thin as you describe. Its a wedge. If its done wrong, it has very little material behind the edge and then curves back out as it approaches the edge. If you pinch a hollow ground blade then try to hang onto it as you pull it away, you wont be able to if its done right. If it flares back out, you feel it and you'll be able to hang onto it where it flares back out.

I'll pass on the sod buster and wait patiently for my chance to get a Halfrich backpocket. Jack, I don't mean to be confrontational. Just trying to pass along some things I learned that really impressed me.
 
RAN said:
Now How was his Backpocket?
Click to expand...

In a word, excellent!! He's made two now. The one in the pic is off a Winchester pattern and the second one, not quite complete yesterday, is off the Bose pattern. The blade was ground so well, that even unsharpened it cut. It was hard to believe from looking at them that he hasn't been making them for years. He got the flush joint just perfect, the spring well regulated closed, half, and open. Centering isnt even an issue. The pics were off my phone. Wish I'd taken a better camera along.
 
Wow, I went to school in San Marcos for years and I had no idea that there was a knifemaker working there. Very cool.

James
 
That's a very nice looking knife. I have to agree with jackknife, I've done this test with several knives successfully, it's not extremely hard, but not trivial either. It sure is fun to get ahold of a *real* slicer, isn't it?
 
jackknife said:
Those are very nice looking knives in your hand there.

3/4 inch green wet limb in one cut? Not as hard as you think, green wood cuts easy. This is when the wood will be at its easiest to cut. And it looks like he used a shallow enough angle to take at least twice the thickness. Any well sharpened larger bladed knife like a sodbuster or Daddy barlow or large trapper will do that if you have it sharpened right. At that point its just as important to have a good sized handle to push with. But he's right, it has to be made with a slight taper and ground thin. Alot of modern knives are not made this way, their stamped out blades with high angle dubbed on edge not being too sharp. A knife magazine tactical will never do it! Hollow grinding is good for a thin sharp edge, but at the cost of not leaving as much steel right in back of the edge for strength. One of the major things about a hollow grind is that it's easy to do if you have a small diameter wheel on your grinder. A harder knife to make by hand is the convex blade, like the Opinel, or a long flat grind like on a large Eye-brand sodbuster. What is interesting to see is take an open Opinel, and lay a small ruler or other strait edge across the blade from spine to edge.

I've made very similar cuts with my larger sodbusters and number nine Opinel when gathering sapplings for the hiking staves I made for all the family one Christmas.

But if you set that branch aside for a couple of months in a cool dark basement to dry and start to age, you have a way different story. Box elder is not that hard a wood, but try that with hornbeam or white oak or shag bark hickory.

The other famous makers knife only went 1/3 of the way and bound up? It had to be dull not to go even half way in soft green wood, or really profiled very thick.
Click to expand...
I've never heard anybody that had ever ground a blade say it was easy. A convex grind is the easiest to do. It is easy to talk a mean game of snooker,rackem up.
 
Nice post. His knives look good and if the fit and finish is tight, he has a good start making slips.

I've ground 3 sets of the BP pattern blades. 1 on 10" and 2 on 14" wheels(that's one in my avatar). I personally find that grinding on a 14" wheel is easier than a 10". I have to say that grinding a blade is easy if you don't care what it looks like when you're done. I takes some skill to make a blade look good and get the symmetry correct.
 
Thanks Ed..Looking really good I'll post up the picture of my Halfrich guide
he is definately passionate and talented..one to watch
Anyway you look at it those cuts are butter clean...
My Boses Pop hair but what is really impressive is Ive done rope cuts with em and they still pop a light strop when needed but that blade is ground right! 100 % work edge

I looove that A2 blade on your T Bose..and Kerry I'm just waiting for you to open up the books!
 
FastEddie, if he keeps up that good work, he could change his last name
to FullRich soon ;)

Nice looking folder and a good test, I'm always cutting things up, testing things, I sometimes think I could get a job making confetti :)

Another test of the edge geometry that I like to do is see how well a knife will
cut into a paper back book, some knives will make an impression but not push
cut through, due to the thicker area behind the edge, give it a try and see how well it cuts, here is a quick shot of my mini-cyclone;

book.jpg


G2
 
Hehe, they certainly should have, it wasn't too bad, light reading ;)
But, it's an easy test to try, just be sure your better half has finished
with the book before you go a pressing away :)
G2
 
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