h a l f b a k e r yWhat was the question again?
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Archimedes has a monopoly on the threading industry. IF any one wants a threaded screw chances are it's going to be some type of helical coil. Well those days are over!
Picture an ANSI Key way, but instead of being straight. It would be in a sine-wave shape, normal to the surface of the shaft. Machine
1-4 of these keyways into a shaft and make a bolt with small pin like nubs at the same wavelength as the sine wave.
Now you would never forget which way to turn a bolt. It would be rotated 45 deg back and forth. Great for areas with low clearance. And to prevent back-off from rotation
At the bottom you could put a catch so positive pressure would be needed to start the unscrewing processes. Likewise you could slighty phase the sine waves at the end to increase friction friction on the pins.
With modern machining practices it wouldn't be all that hard to machine.
[link]
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Anansi Kiwi - a spider shaped green Australian fruit |
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Great. Just when I had memorized the naughty
verses of the engineers hymn, and pithy sayings like
"righty-tighty, lefty-loosy", [metarinka] has to go and
screw it all up. What now? Back and forth to tighten,
and forth and back to loosen? Doesn't have the same
ring to it... |
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"Great. Just when I had memorized the naughty verses of the engineers hymn, and pithy sayings like "righty-tighty, lefty-loosy", [metarinka] has to go and screw it all up. What now? Back and forth to tighten, and forth and back to loosen? Doesn't have the same ring to it..." |
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I work in the gas industry and it's a common to find left hand and right hand thread depending on the type of gas. Nothing like stripping a threaded brass fitting because you were trying your hardest to loosen it. |
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This way you would have an impact wrench that would simply reverse direction every so many degrees. If you were pulling on the head it would loosen, if you push it would tighten. |
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Great. Just when I thought I could delete my off-
topic post, [metarinka] has to go and quote it in it's
entirety. |
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So, OK, fine.. the wavy grooves running along the
length of your shaft (*blushes*) have to be in-phase
for the pins to engage. But if that is the case, there
will be a spot on the sinusoidal curve where the
groove is parallel to the length of the screw, and
provides no clamping force. At that position, it will
not even move under the influence of torque! |
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How do you pull on the head of a bolt with an impact
wrench? |
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"but if that is the case, there will be a spot on the sinusoidal curve where the groove is parallel to the length of the screw, and provides no clamping force" |
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This is all a function of thread geometry. At the transition point when you switch torque directions the only way for it to "know" whether it will unscrew or screw is based on the applied force on the long axis of the screw. |
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This is a big point of the design as the screw would be impossible to backout with coordinated torque and vector force both in the right direction. Hence vibration and rotating force would never back the screw in or out more than half a sine wave. |
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it also can be a security feature because it would be very hard to apply upwards force on counter-sunk screws. |
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I think I need a sketch to be sure, but it sounds like you've got a really small bearing surface here. |
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Most bolts are designed with thread pitch and depth (and nut width) such that under tension, it's not the thread that fails, but the shank of the bolt. This is for a number of good reasons. Also, most bolted connections are designed such that the bolt stretches when tightened ie the thread grip must be strong enough, and the thread pitch fine enough to enable you to stretch the bolt. In your design, I don't see you being able to provide anywhere near that kind of bearing surface. |
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If you want a simple to use fastener with not much tensioning capability - use an interrupted thread instead. Very strong, very quick. |
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