Knife making competition 2013

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HillBill

Bushcrafter through and through
Oct 1, 2008
8,113
57
W. Yorkshire
The little cost as possible was my plan with the Bowie i did. If i had stayed with yew and not switched to blackwood, it wouldn't have cost me anything. I ain't gonna make a standard type knife....wheres the fun in that :D.. This time i think i'm gonna go for something special. Like you, its for fun for me. A reason to go a bit mad and do something different.



Not sure yet. I could easily make a knife for less than £50 (even factoring in the greatest expense that is fuel). The question then is, if I do, what to make? Obviously I can't just make 'a knife', that would be too simple :D

So, IF I do enter, shall I make:

A) a knife with as little total cost as possible (recycled steel, free wood, homemade charcoal fuel, etc)

or

B) a knife that comes in at £50 of materials (though it comes to £65 including the sheath according to the rules)


I'd only be entering for fun, not to win, so don't expect me to make a sinsible knife (or take it at all seriously!) :nana:
 

Jack_D

Full Member
May 11, 2009
72
0
50
Midhurst
Grind height and angle are interrelated. For a given thickness, one can be worked out from the other using trig. Calculations based on right-angled triangles are done using SOH-CAH-TOA. For this, TOA can be used - TOA means "the tangent of the angle is equal to the opposite divided by the adjacent". The opposite is the length of the side of the imagined r/a triangle that is opposite the angle we want to find, and the adjacent is the length of the side that meets the angle we want to find. The opposite and adjacent are the two sides that have the right angle between them.

We know the opposite - it's half the thickness of the blade. What needs to be decided is whether we start with a grind height to get an angle, or start with an angle to get a grind height.

I'm not a knife maker, but I would have thought that it's desirable to have a certain amount of meat behind the cutting edge to make it less likely to chip, but not too much so that it can still cut and slice. If we assume an overall angle of 20°, the grind height can be calculated, but we need to transpose the formula (which, as 'TOA', is set up to find the angle from two known sides).

It starts with Tan = Opp / Adj

We know Opp (opposite) and we know Tan (tangent of angle), and we want Adj (grind height).

When transposed, it becomes Adj = Opp / Tan

We need the half angle to work with a r/a triangle, so our angle is 10°. The tangent of this is 0.176. To get the grind height, divide the half-thickness by the tangent...

1.5 / 0.176 = 8.5mm


On my woody copy, I get a grind height of about 8.4mm (measuring along the flat surface of the blade - not along the sloping part of the grind). It's 4mm thick, giving a half thickness of 2mm. To find the angle on this knife...

Tan = Opp / Adj
Tan = 2 / 8.4
Tan = 0.238

To get the half angle, find the arctangent of 0.238, which my trusty calculator tells me is 13.39°. A full angle of very nearly 27°.

If you wanted to use that same angle on a 3mm blade (to get a similar amount of meat behind the edge), you'd do...

Adj = Opp / Tan
Adj = 1.5 / 0.238
Adj = 6.3mm

Thanks for your efforts there Nomad - 6.3 seems about right for the size of the knife. I appreciated the effort to explain the maths behind it, I may need to read it a few more times though.

Jonathon
 
N

Nomad

Guest
Thanks for your efforts there Nomad - 6.3 seems about right for the size of the knife. I appreciated the effort to explain the maths behind it, I may need to read it a few more times though.
Just keep a note of the calculation bits. ;)

I think it generally starts from a desired angle, so half blade thickness over the tan of the half angle is all you really need. ( A = O / T )
 

Skaukraft

Settler
Apr 8, 2012
539
4
Norway
Well, why not.
I'm in if you allow foregin prticipants:)

A Frosts Lapplander 75 blade with birch burl scales.
 
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plastic-ninja

Full Member
Jan 11, 2011
1,676
39
cumbria
I ain't gonna make a standard type knife....wheres the fun in that :D.. This time i think i'm gonna go for something special. Like you, its for fun for me. A reason to go a bit mad and do something different.
A thought for Mark and Dave.How about making a knife without any steel? Any other materials acceptable.It would be different and also a handicap.:bandit:
Just a thought though.
Cheers , Simon
 

HillBill

Bushcrafter through and through
Oct 1, 2008
8,113
57
W. Yorkshire
No steel? Doesnt leave much does it :) Flint, obsidian..... iron....... bronze..... stone... any more for any more?
 

Dave Budd

Gold Trader
Staff member
Jan 8, 2006
2,755
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Dartmoor (Devon)
www.davebudd.com
interesting idea. I have a knapped blade that a friend gave me a while back (my flint knapping is passable but not upto lovely bifaces sadly :( ). and I can certainly do the whole cast bronze thing.....

Nah, I like my ferrous metals :pirate: I could go iron and steel that I make myself ;)
 

Mesquite

Anyone for sailing?
Mar 5, 2008
23,627
799
58
~Hemel Hempstead~
I've been asked if the combined total for a knife and sheath (£65) can be put towards a knife kit where all the materials for making both are included in the kit.

That is perfectly fine so long as there's before pics of everything and the completed knife and sheath are entered in the appropriate sections. If you don't enter both items then the one that has been entered will be disqualified.
 

JohnC

Full Member
Jun 28, 2005
2,624
74
58
Edinburgh


I got started this afternoon, I had a car spring I found when out running last week, plus another one I'd found some time back and straightened out before.




Id got my "forge" out, and hooked it up to an old hair dryer..



a variety of tools, gloves and goggles, Ive an old section of rail for hammering on...




I got as far as straightening out the longer piece and flattening out the shorter one, the metal is pretty tough and I needed to get it very hot to do anything, the charcoal is ordinary B&Q stuff...

It was getting late and I dont like to make too much noise into the evening, so I stopped and checked the small piece against the "plan"...



So far so good, Im not sure how heating and re-heating affects the metal? Ive let them air cool so far.. Think I need to hit harder and/or faster..... Ill have a go at more thinning of the blade next time, then squaring the tang down...
 
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Mesquite

Anyone for sailing?
Mar 5, 2008
23,627
799
58
~Hemel Hempstead~
That's a nice start John, I do like the look of your design :)

So far so good, Im not sure how heating and re-heating affects the metal? Ive let them air cool so far.. Think I need to hit harder and/or faster..... Ill have a go at more thinning of the blade next time, then squaring the tang down...
I'm sure our resident blacksmith guru Dave Budd will come along soon and let you know if it affects the metal
 

Dave Budd

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Jan 8, 2006
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JohnC, Good effort! :beerchug: Nice to see somebody not falling into the idea that a forge is a complicated thing that takes weeks to build and lots of kit to do. All you need to forge stuff is a container to hold fuel, an air supply,a way of getting the air into the container and then fuel. Nothing fancy needed, just don't get hung up on what you think you need ;) All I use is a hole in the ground, clay pipe and bellows. I also use 'just BBQ charcoal', but then there is no other sort aside from briquttes :nono:

Regarding heating your metal. As long as you didn't get it white and sparkly*, then you can reheat it as often as you like. You should be working that stuff in the red to orange range. If it gets to a bright orange/yellow then you run the risk of it falling apart and if you hit it when it is no longer red (or a very dull red) then you are likely to get cracks in it. When you are done forging it, you will want to normalise it a few times. That's heating to a uniform orange and leaving to cool in still air, this will refine the grain structure of the steel, relieve stresses built up and make it easier to grind/file. The key is a uniform colour; if the end is much brighter then it may air harden and the file won't touch it, in which case reheat to a dull red and leave to cool.

Looking forward to seeing how it comes on :)



* If you did gets sparkles, chop that bit off and reforge the burnt bit is knackered!
 
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JohnC

Full Member
Jun 28, 2005
2,624
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Edinburgh
Hello, thanks for the advice Dave! I shall make some notes from that for this weekend. I did find it was easier as the light faded to judge colour, so I may set up some shade..
 

Dave Budd

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Jan 8, 2006
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yeah get a shade. Even just something to cast a shadow like a wheelbarrow can help. when you think it is hot enough take the metal out and put it in teh shade to see how hot it is and then to the anvil or forge depending on what you see ;)

Direct sunchine is a pain, you can't see how hot it is and you will end up burning it! Although as the light fades you can think it is hotter than in reality because it glows brightly. can't win :rolleyes:
 

JohnC

Full Member
Jun 28, 2005
2,624
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Edinburgh
I did a bit more the other weekend



I used a grinding wheel to rough it out, I have used files before now for making a knife, so I know it can be done, but it does take a while..

I was getting happier with the general shape..

I cut a thread on the end to take a nut.

I'd shaped the knife blade, but not sharpened it too much as I've burned off the edge of a blade before.
The smaller piece is for a hook knife and to use as a test piece for tempering.


I got the blade to a decent heat and checked it with a large magnet, when the steel becomes non-magnetic, it is (I am told) an indicator of a change in the structure and a good time to quench it..

I used old vegetable oil, but old engine oil gets used as well. Sometimes flames up or spits...

I cleaned up the scale on it and checked with a file, it scraped over the top without biting in, so I reckoned it was hardened..

I'd read and seen a block of metal being used to temper the metal, I'd had this heating as well..

I held the test piece to it and gota play of colours as it heated. I believe this is oxides forming at different temperatures and can be used to judge the "hardness" of the piece. I was looking for a straw colour..

Test piece doen I went ahead with the blade..