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So, I am looking to design a knife.

Posted by Agith 
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So, I am looking to design a knife.
August 24, 2012 02:35AM
I am looking for a good work horse for my collection ( Though I would like it to be something perhaps a bit quirky? )

I am not too sure how the hell I want to have it, though I do like the billhook and the kukri designs ( Not sure however if a splice of those, using a billhook type end would really work though.) And I have never used a larger knife as I am hoping for this to be.

So....I'd love help on the matter.
Re: So, I am looking to design a knife.
August 24, 2012 02:44AM
What exactly are you looking to do with it? What should it do really well. What should it do ok? What doesn't really matter much at all.
Re: So, I am looking to design a knife.
August 24, 2012 02:47AM
I am not at all worried about penetrative ability. This is going to be more of a brush clearing chopper/utility knife. I want it to be able to maintain finer detail while being an alright chopper. Digging is a pleasant bit, though I am thinking of a flat headed front on the blade for that, and the bill hook portion will be for dragging along and into to cut into the brush.

This is a very impulsive thought at the moment, so I am working on developing it more and will do so throughout the week, and post my thoughts as I do so.
Re: So, I am looking to design a knife.
August 24, 2012 12:48PM
Wait you want each of those to or you wanna combine them into something crazy like a billkri? Or a kukhook?
Re: So, I am looking to design a knife.
August 24, 2012 02:16PM
Hehe, I think that'd be oddly useful. Perhaps I am wrong in that regard?

Here is a basic picture which perhaps may be necessary.



( Ignore that line going inwards, that's just my dog having scared the shit out of me just now and my hand flinched...Plus I am not gonna redraw it since the idea is the same. )
So basically I am looking at a billhook with more of a belly to it ( Perhaps a differential grind would be ideal for a more outlandish idea like this? Not sure.
Re: So, I am looking to design a knife.
August 24, 2012 04:39PM
Quote
Agith
Hehe, I think that'd be oddly useful. Perhaps I am wrong in that regard?

Here is a basic picture which perhaps may be necessary.



( Ignore that line going inwards, that's just my dog having scared the shit out of me just now and my hand flinched...Plus I am not gonna redraw it since the idea is the same. )
So basically I am looking at a billhook with more of a belly to it ( Perhaps a differential grind would be ideal for a more outlandish idea like this? Not sure.

That makes me think of a Woodsman's Pal...
Re: So, I am looking to design a knife.
August 24, 2012 06:39PM
Agith would you mind if I took a crack at drawing it? I think I know what you're going for there
Re: So, I am looking to design a knife.
August 24, 2012 07:15PM
I wouldn't mind at all smiling smiley. I don't think that woodsman's pal has the belly I am looking for however.
Re: So, I am looking to design a knife.
August 25, 2012 01:44AM
And it makes me think to a roncola lucca (italian billhook pattern), amongst billhooks that are still in production. There were many french patterns with even more belly, but not a single company making them survived.



The problem with making a billhook type of knife/tool, is you either have to get a very wide sheet if you're doing it in stock removal, and there is lot of waste, or either forge it (which is also the best way to get tapers).
Re: So, I am looking to design a knife.
August 25, 2012 02:57AM
Hmm, looking closer to what I was looking for. THough couldn't that same stock material be used for other knives as well? i do see the concern with waste however.

Do you think the companies died as a result of poor design? Or lack of interest?
Re: So, I am looking to design a knife.
August 25, 2012 03:20AM
Cost of production combined with deminishing demand as agricultural handtools fell out of use in 1st world countries.
Re: So, I am looking to design a knife.
August 25, 2012 03:42AM
Aah, that'd make sense.

Oh to tell Styx, I am gonna call it a billhukri.
Re: So, I am looking to design a knife.
August 25, 2012 08:17AM
OK I'm gonna get on it ASAP.
From what I understand you want a curve of the kuk and the point of a billhook. That Italian billhook might actually help me out a good bit.
Re: So, I am looking to design a knife.
August 25, 2012 09:45AM
This is the first rough sketch



From what I understand you want the billhook front part and the back curve of the kukri.
Re: So, I am looking to design a knife.
August 25, 2012 07:37PM
Yes, design is correct, though it looks as though it'd somewhat weak in the back ( thins out alot. )
Re: So, I am looking to design a knife.
August 26, 2012 08:28AM
Yep. This is where someone who has a kukri would come in handy, or a maker. How thin can it get and at what angle does it break?
I also think that the tip is a bit too pointy
Re: So, I am looking to design a knife.
August 26, 2012 04:51PM
I tried to draw different sketches to mix the curve of a kukri and the tip of a billhook, and however I try, it just doesn't work. Not only it's ugly, but it's also obviously ill-balanced and not fonctional. The curve/belly of the kukri and hook of the billhook are just incompatible, because with a kukri you chop mostly around the belly, and with a billhook mostly with the part before the hook, not only because of edge curvature, but also because of CoG, CoB, weight distribution, etc... If you add the weight displacement induced by the kukri blade curvature + hook, you end with something unusable. You can straighten a kukri, it makes a falcata or kopis, you can curve a billhook upward, it ressembles some rare patterns, but you can't curve a billhook downward and give it the narrow "neck" and the belly of the kukri.
Re: So, I am looking to design a knife.
August 30, 2012 01:30PM
Quote
Madnumforce
I tried to draw different sketches to mix the curve of a kukri and the tip of a billhook, and however I try, it just doesn't work. Not only it's ugly, but it's also obviously ill-balanced and not fonctional. The curve/belly of the kukri and hook of the billhook are just incompatible, because with a kukri you chop mostly around the belly, and with a billhook mostly with the part before the hook, not only because of edge curvature, but also because of CoG, CoB, weight distribution, etc... If you add the weight displacement induced by the kukri blade curvature + hook, you end with something unusable. You can straighten a kukri, it makes a falcata or kopis, you can curve a billhook upward, it ressembles some rare patterns, but you can't curve a billhook downward and give it the narrow "neck" and the belly of the kukri.

It makes more sense to put the belly and hook on opposite sides. That way the weight of the belly still contributes when you use the hook but you have two optimized cutting edges. Yorkshire billhooks are like this:

Re: So, I am looking to design a knife.
August 30, 2012 04:19PM
Quote
thiswayup
It makes more sense to put the belly and hook on opposite sides. That way the weight of the belly still contributes when you use the hook but you have two optimized cutting edges.

I was thinking the same thing... and also thinking about turning a large Bowie into something like that. If a Bowie was long enough you could make a very exaggerated sharpened clip point to hook lighter vegetation and for general cutting duties.

Make the spine thickest right where the clip point starts, and taper it back to the butt as well as to the tip. That should keep the majority of the weight in the front third of the blade even with a very long clip point.
Re: So, I am looking to design a knife.
August 30, 2012 06:18PM
Usually, and that is true from Italy to England, including France, when there was a back edge, it wasn't just the sharpened spine of a simple edge billhook, but an offset straight edge. It could wear off with time and use, ending rounded at the end and getting a curb almost similar to the spine of a one edge billhook, but it's by accident rather than on purpose (depending on the use, it could be the middle section of the edge that could be worn, resulting a wave shaped back edge). It could be relatively long and not much rised, being a real back edge, or narrower and significantly offset, ressembling almost a hatchet bit. Also the clean part near the spine is probably not an edge, it's too thick here to have a working edge that would have such a narrow bevel: it's probably the result of an agressive clean-up, and the deeply pitted surface of the blade indicates it once was heavily rusted.

But it could be possible to give the back edge of a billhook the shape of the first half/two thirds of a kukri. Or we can say it the other way: cut a kukri blade in the middle or last third, and turn the spine into a billhook shape. The problem with having two opposing edges is that you can't baton. It's a bit weird, but should be ok to balance empirically, and not a challenge to wield.

Re: So, I am looking to design a knife.
August 31, 2012 05:48PM
Somewhat based on the previous drawing, and limited by a 100mm wide bar, I made this blank today:





It's a prototype really, but would be usable. Next time (if there is one) the blade will be wider, so the hook will be fully developed. The actual version is a bit off balance: the hook feels not enough in front of the handle axis, while the kukri edge is very offset and feels having an advantage. You can see two red lines passing near my mark: these are axis of neutral balance (my mark is just next to the CoG).



Edited 1 time(s). Last edit at 08/31/2012 06:09PM by Madnumforce.
Re: So, I am looking to design a knife.
August 31, 2012 06:21PM
Wow! Really nice looking... "thing" there Mad thumbs up
Re: So, I am looking to design a knife.
September 07, 2012 12:34AM
That looks nice, though it's worth pointing out that this is a design for the future ( I am so broke right now with buying a car)

IT resembles a fire axe to me at the top. Though the design is pretty great actually ( Perhaps for the section about after the hook, it is made blunt so it may be used as a draw knife? )
Re: So, I am looking to design a knife.
September 10, 2012 11:05PM
Well, I roughly finished it today. Left the scale from HT, just took it to the belt grinder to give it a edge, and pinned the slabs.

After some basic use, and as I feared, the fact it's unbalanced makes the strikes with the kukri edge difficult to control, though otherwise it seems relatively powerfull for the size and crude edge bevel. The billhook side is also a bit unintuitive to use because it's unnaturally recessed. To solve both these issues, I have bought 3mm thick X46Cr13 bars, in 150mm and 200mm width, which should be plent to have a fully developed billhook side that will balance the kukri side. The billhook side acted rather poorly compared to a standard billhook, and even on light vegetation stems, the kurki side worked better. I hope the expansion of the billhook side will cure that poor performance, and make it worth sacrifiying a spine to baton.

But the design has one major security drawback. When I swang that thing in the kukri configuration, especially when chopping a standing tree, on the upward strike of my off side to make the notch, the beak of the billhook side came dangerously close to my stomach, It even cut my tee. Just some centimeters closer, and I would have cut my self very badly. These centimeters, the extra width will give them. Maybe I should be much more careful using it, and develop an adequat technique. Maybe the extra width and some more centimeters in length will increase the power of each strike so I won't have to make wide chopping motions. But maybe that design is dangerously flawed also.



Edited 1 time(s). Last edit at 09/10/2012 11:06PM by Madnumforce.
Re: So, I am looking to design a knife.
September 12, 2012 12:29AM
Quote
Chum
Wow! Really nice looking... "thing" there Mad thumbs up

Yes: definitely the coolest bill hook I've ever seen.
Re: So, I am looking to design a knife.
September 12, 2012 12:32AM
Quote
Madnumforce

But the design has one major security drawback. When I swang that thing in the kukri configuration, especially when chopping a standing tree, on the upward strike of my off side to make the notch, the beak of the billhook side came dangerously close to my stomach, It even cut my tee. Just some centimeters closer, and I would have cut my self very badly. These centimeters, the extra width will give them. Maybe I should be much more careful using it, and develop an adequat technique. Maybe the extra width and some more centimeters in length will increase the power of each strike so I won't have to make wide chopping motions. But maybe that design is dangerously flawed also.

Why not just fit a longer handle? Traditionally bill hooks have never been full tang.
Re: So, I am looking to design a knife.
September 12, 2012 06:46AM
There was one type of billhook that had a flat tang (though not technically a full tang), it was the "coltelle" or "coutelle" from the French Pyrénées:




The problem with a traditionnal tang or a socket tang is that it needs to be forged. And it's not that easy! It also relatively time consuming. Making a real billhook, with all the tapers, would be impossible for me, or I need much more serious equipment (a forge with wide hearth, a heavier anvil, maybe even a drop hammer).
Re: So, I am looking to design a knife.
September 12, 2012 04:09PM
Why not just fit a standard tang of the type you already have into am extended handle? Tufnol is extremely strong - you could use a sandwich of three layers with the middle one the same thickness of the tang. You assemble everything with golf club epoxy, then wrap some expoxy saturated cloth around the join and compress it with a string wrap over cling film. If you're really concerned you could use the bidirectional fibreglass tape used in boating making. Then, obviously, you test it! But tufnol is very high strength, and a few layers of fibreglass type in resin should be much stronger than the wood or horn that traditional tangs are embedded in.