Screws (or more specifically, the drive mechanism on the head of the screw) can look unattractive when installed. This can be overcome with screw head covers, but this is fiddly and can look tacked on.
I want a screw with a head that is completely flat and flush with the surface it's screwed into.
So I propose a screw with: a) the drive mechanism around the edge of the head; and b) a head that can be slid a small way down the top portion of the shank.
To install the screw: - a hole and countersink are drilled - a screw is screwed in with a matching screw driver - when only the head of the screw remains above the surface, the head is tapped with a hammer. This pushes the head down the top portion of the shank into a locked position.-- xaviergisz, Feb 14 2010 illustration http://imgur.com/a/UgIEa [xaviergisz, Feb 14 2010, last modified Dec 12 2011] flush head screw https://v.redd.it/45h1w54jt9v71More complicated and harder to manufacture. Will cost $40 each if he decides to commercialise [xaviergisz, Oct 24 2021] I think this is a good idea, but I can't quite tell from the text or illustration.
Why require a special screwdriver? Why not have a regular slot or philips-head drive, and then use your hammer-tap to make the innards flush with the top surface?
There might need to be some sort of latching mechanism, to prevent the recessed head from being pulled back out under stress.
(+) conditional on further description / illustration.-- csea, Feb 14 2010 The usefullness is sort of dubious. You'd start pulling them thinking they're nails. Then you'd think they were ringshank nails. Then you wouldn't know what to think when you start pulling the heads off of them.
The problem with making the head cone-shaped is that it will be difficult to anchor. A cylindrical head would anchor much better.
Either way if the purpose is for appearances only, you wouldn't want to try to hammer them in flush with a hammer, you would need a punch. And if this screw head is hollow, it's likely the punch will disfigure it or penetrate it.-- rcarty, Feb 14 2010 csea, The top of the head of the screw is completely a flat, unitary surface, hence the need for the screw-driver engaging mechanism being around the edge of the screw head.
Your idea for making the //innards flush with the top surface// is good, but I figure if you're going to the effort of getting a flat screw head, you may as well get it perfect.
rcarty, I'm sure there is some kind of device that could be used to gently transfer the impact of the hammer to the screw head.-- xaviergisz, Feb 15 2010 It's actually better if there's not, then you can invent that too.-- rcarty, Feb 15 2010 Screw then tap, all structural strength is lost--- zeno, Feb 15 2010 //all structural strength is lost//
depends on the strength of the locking mechanism doesn't it?-- xaviergisz, Feb 15 2010 How do you unscrew it?-- xenzag, Feb 15 2010 A cheaper and structurally better option would be to screw your (cross-head) screw in so that the head is about 1mm below the surface of the wood. You'd then stick over it a 1mm circular shim which has a plastic 'x' stuck on the back which fits into the screw head. This would look good, you'd still be able to use your normal cheap screws, it would be as strong as a normal screw, and it would be unscrewable (just prise off the shim).-- hippo, Feb 15 2010 The circular shim is a good idea, but it doesn't quite have the aesthetic I'm after: I want to make a functional element attractive, rather than trying to hide it.
how to remove it? drill a pair of holes co-linear with and equidistant from the center and (obviously) use a screw driver that matches these holes (this is known as a 'Spanner head' or 'Snake-eye' screw according to Wikipedia).-- xaviergisz, Feb 15 2010 Ah right - but I think the functional element, the cross-headed screw head, is already quite attractive.-- hippo, Feb 15 2010 xenzag and zeno are right.
A carpenter uses screws over nails for two reasons: For the extra strength, and so that they can be removed easily if required.
If you tap it, it will deform the wood around the screw and loosen the thread, so you will lose the extra strength. And since there is no easy way to remove them (certainly without damaging the wood - although I don't understand your strange method of removal)*, you might as well just use nails anyway. They can easily be made to sit flush and are can have completely flat heads as well.
*Obviously a powerful magnet could pull the head out so that they could be unscrewed - and pushing them in by hand would be easy and prevent damage to head or thread.-- Mrlemonjelly, Feb 15 2010 With a normal screw, the head itself pulls the top part tight to the second part, but in this case, the head never makes contact until after the screw is set. How do you pull the two parts tight? It seems the final tap with the hammer is all you get to tighten the parts, a one time deal. If it's not right, how do you re-set it?
I'm having trouble imagining applications where this would work.-- oxen crossing, Feb 15 2010 I was thinking the countersink depth and initial screw depth would be accurately controlled with the tools (with stop-depth mechanisms), so the tap would lead to a near-perfect flush head.
Yes, the tap is a one time deal, so make sure it looks right before you make the tap. I envisioned the locking mechanism would be ratcheting barb(s).
Good point about loosening the screw when you tap it; I hadn't considered that.-- xaviergisz, Feb 15 2010 the back of a screw head is a very important functional part of the screw. For this to work, you'll need to have the screws screw into a recessed hole in the wood.
Might I suggest an alternative mechanism for making the head lie flush?
Build the screws in two parts. When pressure is applied, and the head is turned clockwise, the screw screws in. When no pressure is applied, the screw head can turn counterclockwise independantly of the threaded shaft. A quarter turn would allow it to fall down into slots, and you might then be able to lock it in place by turning it via a magnet. (the force to lock it in place, or later unlock it, if needed, is of course less than to drive it into the wood.)-- ye_river_xiv, Feb 15 2010 How about just screw the screw in a little deeper than the surface and pop in a plug or use putty...etc....-- ShaneSezWhat, Feb 15 2010 Hey, pretty interesting. [+]-- doctorremulac3, Jul 22 2014 The screw has a countersink and a hollow splined shaft, like a Torx, running for 50% of its length.
Drill a pilot hole.
Screw in the shank using the special driver bit until the countersink is just below flush.
Push the blanking pin into the hollow shank, where it is retained magnetically.
To release, apply the electromagnet-based removal tool to the head.
Et viola.-- 8th of 7, Jul 22 2014 Only works if you have a double head, since, as several posters pointed out, the head is what serves to pull the two parts together. This would also set a fairly deep minimum thickness, since you're going to have enough counter-bore to take the lower head, and have enough depth for the upper head to grip the sides of the bore.
Not saying it can't be done, but I think wood putty or the little snap in caps end up being less of a hassle.-- MechE, Jul 22 2014 This is an excellent idea!
The solution (as with so many things) is magnets.
Make the hittable part out of steel, and magnetize the whole thing so that the top part is gently pulled into the body by the magnetization.
Then, if you want to undo the screw later, a strong magnet (maybe built into the driver) will overcome the force holding the top part and pull it out, ready to be gripped and unscrewed.-- MaxwellBuchanan, Jul 22 2014 aka bolt-- popbottle, Jul 22 2014 Reduce the size, use a gibb screw gun to insert the inital shaft to the correct depth. Push in a choice of two magnetic covers giving a dot array of any S and N pattern. Outcome, a designed magnetic surface.-- wjt, Oct 24 2021 random, halfbakery