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Hopefully material science can come to the party.
A screwdriver tip made of ultra strength, 0.25 mm diameter ended, pins arranged in a circular matrix. When pressed into the desired screwhead, the needed form is moulded and locked for use.
Screw to you hearts content.
Just unlock for a new
screw type or change size if you really have to.
telescoping_20torx_2fallen_20tool
[xaviergisz, Feb 27 2013, last modified Feb 28 2013]
Existing tool, works on the outside of worn bolts
http://www.amazon.c...ocket/dp/B000065CJ8
[Vernon, Feb 27 2013]
[link]
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What magic material will this 0.25mm screwdriver shaft be made from? |
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Yes, I'm thinking this will work to no extent. |
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A bundle of thin rods has very little stiffness in
bending, and the net result will be something like a
screwdriver made out of hard rubber. |
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Here's a variation on your idea: a screwdriver (or Allen key)
with telescopic sheaths that can be slid on/off to make the
tip have an adjustable size (actually, now that I think
about it I think I might have seen this on HB before). |
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This Idea reminds me of an existing tool for gripping the deformed heads of bolts (link). The main difference is that the moving pins of the existing device surround the outside of the bolt-head, while in this Idea the smaller pins would fill the slot or cross or square or hexagon or whatever, in the head of a screw. |
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I don't know to what extent [MaxwellBuchanan] is correct in saying that the small pins won't be able to handle the load, because, per the link, it is obvious to me that those pins are being supported by lots of surrounding pins. |
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I will recommend, however, that the shafts of all those small pins be hexagons or squares, and not be round (like in the link), to increase their ability to support their neighbors that are "in the slot" and are experiencing torsional load. |
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The narrower the pins are the worse it gets, because the gap between the pins will be roughly constant but will be an ever-increasing proportion of the total width - and it is this that determines the tip's flexibility. |
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If there's an external collar surrounding the pins, which extends down to the point of contacting the surface around the screwhead, that will minimize the unsupported length of pins. Doesn't eliminate the problem, but it might make the device usable. |
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The problem is that if your screws are harder than
your pins, they will tend to deform and not slide. |
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If your pins are harder than your screws, this will
tend to round out corners, simply because pins won't
land perfectly in the driving feature, so force will be
applied unevenly, and slightly away from the corners. |
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And ignore the locking bit, because that's going to be
just about impossible in any durable mechanism. |
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I don't believe the gator grip actually locks. The
problem with a friction/squeeze grip is that
anything that had enough play to lock the center
pins would have enough play to allow pins to bend
around the bolt head. |
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And there is generally a difference between an
interior and exterior driver with regards to where
the peak load is applied on the tool. Also the pins
on the exterior driver can be backed up by a solid
outer wall. The pins on an interior driver cannot
be backed up by anything if you truly want this to
handle all driver shapes. |
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I broke three Gator Grips before I gave up on the things.
They work well, but they don't stand up to industrial use. |
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The fact is that a bundle of narrow pins will have less bending strength than a rod of the same mass. [Hippo]'s point about inneficient circular packing is correct, but also misleading. |
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The term you're missing is transverse shear. |
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One steel flat bar 10mm thick is much stiffer than 10 X 1mm bars stacked together. By binding the bars together with increasing strength you can approach the stiffness of the 10mm bar, but ultimately you'll never match it. This is because as the stack of bars bend, they slide across each other. In the solid bar this sliding effect is resisted by the shear strength of the steel. A useful analogy is the epoxy or binder holding the fibres in a carbon or glass fibre composite together. It's there to resist shearing between filaments. |
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Most people don't "get" transverse shear. |
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Anyhoo, I think what [Vernon] is referring to doesn't rely on the bending strength of the rods because they're enclosed, and just relies on their hardness and friction. |
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I chose a circular shape of the pin because I imagined any other shape with corners being lipped by the form it is trying to model. Though, it any comes down to sampling size the smaller the pins the better the model fit but the stronger the material has to be. Maybe the pins need a point to try to catch lips and internal curves such as in the corners of pozi-drive. |
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Maybe a Ferrofluid can be lowered between the pins. |
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