This is two square nails in cross-section that are weakly joined side by side to form a rectangle in cross-section. The heads of the two nails would be strongly joined together. The two tips of the nail would be wedge shaped so they diverge from one another as the nail is driven. The result is a nail that has split into two curved metal shafts joined by a common head. This should be exceedingly difficult to remove, so don't drive it where you don't want it to stay.
-- saprolite, Mar 08 2009

US patent 4179975 http://www.google.c...AAAAEBAJ&dq=4179975
A self anchoring nail with a longitudinal split [xaviergisz, Mar 09 2009]

I understand what you want it to do, but I don't think it would actually work. I think they would just go in parallel. I don't think the wedge would do anything. There would have to be a space between the tips, so the nails go in at an angle.
-- plasticspoon, Mar 08 2009


[pspoon] yeah...I think softwoods would be the most problematic
-- saprolite, Mar 08 2009


A sort of dum-dum nail?
-- AbsintheWithoutLeave, Mar 08 2009


[plasticspoon] I actually think this would work just fine, I have used a brad nailer for years and have found that using a too long brad causes the nails to curl around hard and come out the side of the work piece. I think the key here is these could only be so thick before they would become too inflexible to allow for the split to occur.
-- jhomrighaus, Mar 08 2009


[Absinthe] sort of...hopefully with negligible compressional distortion along the long axis of the two shafts
-- saprolite, Mar 08 2009


The shape of the tips should roughly control which direction the two nail halfs travel in. I'm thinking of a W shaped nail head for this, allowing some wood to be caught between the tips.
-- Worldgineer, Mar 09 2009


A tip with straight outer edges and curved inner edges should produce some of the desired result. Imagine the slashes with a shallow belly curve towards the center.
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It will definitely work better in harder woods. In pine it would either have to be a very soft metal or a very long pre- separated point to have any chance of bending.
-- MechE, Mar 09 2009


I guess you could always bend the nail yourself a bit too before you hammer it.
-- plasticspoon, Mar 09 2009


(+) That's hittin the nails on the head.
-- 2 fries shy of a happy meal, Mar 09 2009


You should include an explanation of why we would want to have nails that are impossible to remove and bend off in unpredictable directions.

I don't see the use, personally. Wouldn't this just make it harder to build things without screwing up and harder to recycle old wood?
-- Smurfsahoy, Mar 09 2009


//You should include an explanation of why we would want to have nails that are impossible to remove and bend off in unpredictable directions.//

Squeaky floors.
m'just sayin.
-- 2 fries shy of a happy meal, Mar 09 2009


//impossible to remove//

I'm told that in certain high-crime neighbourhoods (specifically, South Africa), it's normal to use un-removable screws to fasten security grilles to window frames, so maybe there's a comparable use for this idea.
-- pertinax, Mar 09 2009


[Smurf] [ 21Q] This nail would definitely be a beast to remove without ripping off the head or tearing up some wood, but the point is it will also hold fast. The problem of nails backing out is what I was trying to fix. Some "back out" will still occur from the drying/shrinking of the wood, but one good whack should fix it if that happens. The directions this nail would diverge should be far from "unpredictable." Only two really, out each side. The degree of divergence should be between nil and whatever is allowed by the specific angle in the angled tips (barring striking something like another piece of metal). You should have a good idea about the overall divergent width from trial and error (often a lot of error), so don't drive it too close to the edge of anything (with divergent trajectory towards the edge). Also, this nail would be problematic for removal and recycling, but I'm trying to build something that will hold together under tough conditions, not recycle it. Applications could be decking, modular construction, or plain old framing. A gun would probably be the best way to drive this.
-- saprolite, Mar 09 2009


Re-inventing the wheel is what we do here. So that is why we need this nail. [smurfs]
-- blissmiss, Mar 09 2009


Security (crimewise and structurally) and squeaky floors are good answers.

I'm still concerned about unpredictability, though. Normally, yes, it would just go in two known directions, but especially since, as has been mentioned, this is mostly for hardwoods, if you come anywhere close to a knot or dense area (in interwoven grain lumber), you are way more likely to have nails curling up around, snaking through the wood in weird ways, etc. Plus, whenever you get anywhere near a corner, it's very difficult to place one of these without some surprise cracking of the wood from who knows which direction.

I think a rivet would do much the same job in most situations without that unpredictability.
-- Smurfsahoy, Mar 09 2009


I am not that convinced it would be that difficult to remove, compared with how difficult it would be to get it to go in.
-- Frank3, Mar 09 2009


//Security (crimewise and structurally) and squeaky floors are good answers.//

That's one of the ways the Samurai guarded against ninjas so it must be good, but I think I'll just stick with soundless floors and a good dog.
-- 2 fries shy of a happy meal, Mar 10 2009


Thinking about this further, it seems that barbs would be the best way to make a nail stay in place. Of course, such nails already exist - they have ringed bumps along their shaft for her pleas... I mean to keep the nail in the wood.
-- Worldgineer, Mar 10 2009



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