Knife Thread

[Brian the brain]

Hmm...pneumatic-ballistic bajonet.......
That would be a cool addition to any project...

I guess you'd be a hit on youtube....

[jackssmirkingrevenge]

here's a brain fart, a "valveless" launcher that could fire an unmodified knife with an appropriately shaped handle silently...

[jakethebeast]

jsr, what kind of attaching method you are going to use? just thinking that what kind of tang im going to forge to it...

[jackssmirkingrevenge]

Is it possible to have a short cylindrical one?

[jakethebeast]

thin and round you mean? just thinkign that the balde is going to be like 5mm thick from the thikest part so it would be pretty weak spot... our ballistick knife has m5 thread on the tang but i dont know if the powerfull penumatic version would hold it so well...

[Zeus]

JSR, it would indeed fire the knife, but it would absolutly f*** the blade. My L1A1 bayonet was used as a throwing knife by some fool, it's got a horrid ding in the blade and the tip won't sharpen well anymore.

I hold onto the bayonet as it's the closest I'll get to owning a L1A1, unless I become a dual citizen and hang around MrC 6 months in the year.

[jakethebeast]

it depens of the material, heat treatmen and tempering of the blade

[jackssmirkingrevenge]

thin and round you mean? just thinkign that the balde is going to be like 5mm thick from the thikest part so it would be pretty weak spot... our ballistick knife has m5 thread on the tang but i dont know if the powerfull penumatic version would hold it so well...

I can have it threaded? a short length of M5, say about 2 cm, sounds about perfect. Remember that this part won't be under any real stress with a lightweight synthetic tail.

Give me a couple of minutes and I'll draw up a diagram.

it depens of the material, heat treatmen and tempering of the blade

... and what you're throwing it at, and how good you are at it - if you're shít and been practicing over hard floor, well...

[inonickname]

thin and round you mean? just thinkign that the balde is going to be like 5mm thick from the thikest part so it would be pretty weak spot... our ballistick knife has m5 thread on the tang but i dont know if the powerfull penumatic version would hold it so well...

For a knife that's made to be shot I'd use thicker spring steel (at least 6, preferably 7 or 8mm) with higher grind angles and duller edges. Only the point needs to be particularly sharp. Temper it to only moderate hardness to prevent chips/cracks. I wouldn't bother with a good finish either, if you fire it, it's going to look like trash.

And JSR, tang length is basically irrelevant, the point where the blade reduces down to the tang is a massive weak spot due to the amount of moment (torque/leverage) the blade has on it, and it's small diameter. It needs to be beefed up, especially for a ballistic knife.

Edit: Hmm, didn't think of the light weight of the tail. I'd still go with thicker spring steel for the blade. Don't have any? Well cut up a leaf spring and beat it flat (either heat it up first or tie a noose for yourself). You will find few steels that are more bastardly to work, but nothings going to damage it. I have a bowie I made from a leaf spring that can be used as a blocksplitter, then used to shave with after. It's hard metal.

[jakethebeast]

yeah i was just thinking to get the blade semi-light, 5mm thick 0.8C carbon steel would be good, its pretty tough steel and the thinckness is ok, and of course with very high grind angle, but still razor sharp

EDIT: yeah i have 150cm x 3cm x 10cm truck leaf spring, im just lazy

[jackssmirkingrevenge]

This is how I picture it:

[jakethebeast]

that blade is pretty wide, so if i make it that way it would not be strong enough... let me draw you a picture...


EDIT: nah, with my drawing skills that was impossible but you see, the dagger blade in your picture has pretty low grind angle, so its not strong enough... the attaching metod i was thinking was to weld a piece of m6 thread to serve as tang, that would be soft material and it would hold pretty well...
to get enough high grind angless, i need to sand them, forging so high angles is very hard

[inonickname]

that blade is pretty wide, so if i make it that way it would not be strong enough... let me draw you a picture...


EDIT: nah, with my drawing skills that was impossible but you see, the dagger blade in your picture has pretty low grind angle, so its not strong enough... the attaching metod i was thinking was to weld a piece of m6 thread to serve as tang, that would be soft material and it would hold pretty well...
to get enough high grind angless, i need to sand them, forging so high angles is very hard

Agreed, the angles in the FS (that probably play a big role in making it an appealing blade to you, JSR) are shitty for a throwing/ballistics knife. If you look at grind angles on throwing knives they're really high, like so:



You really need those high angles for any kind of impact. Good news is grinding them is quicker and easier than big bevels (but like Jake said, you basically can't forge them).

[jackssmirkingrevenge]

Hmmm... That shape isn't very appealing though.

How about something like this?



Remember this is travelling head first, unlike a normal throwing knife.

[jakethebeast]

That looks that it could take some beat, and looks like easier to make