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A bolt and (undersized) nut which only fits
on the bolt when heated, and gives a really
secure
never-going-to-loosen-on-its-own fixing
when cooled.
Forbes: "The Taming of the Screw"
http://www.forbes.c...0919/066_print.html
Not 100% related but an interesting anecdote about what can happen when you give somebody time to think deeply about a problem. [bristolz, Sep 30 2005]
[link]
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it would be tricky if you really wanted to remove it. |
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like I said //it would be tricky if you really wanted to remove it.// |
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sheesh, some people say it in 11 words... |
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If you use an extra long bolt, and tighten the nut down, then sort of whack the end of the bolt over flat with a hammer, it is hard to get the nut off. |
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//It's also common to heat stubborn or rusted nuts because the heat causes the nut to expand thereby making it easier to remove.// |
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Just out of curiosity, why doesn't the bolt expand too? Or does the nut expand more because it's smaller? |
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it may be that the nut has more surface area so heats faster than the bolt, or else the bolt is heavier so it heats slower. |
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[Ian T]: The bolt expands as its cross-section increases, but the nut expands more, by its circumference increasing. This really would work. At the garage where I used to work, the fitters would often take a torch to a stubborn nut. However, locking nuts (particularly the Simmons type) are so efficient that I'm not sure it would be necessary. |
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//increasing heat doesn't simply 'scale up' the size of the metal//
If you heat an annulus, its outer diameter obviously increases but so does the inner diameter. Imagine that it's made of small, discrete, keystone-shaped sectors; now move them slightly apart and add another one. The metal rims of wooden cart-wheels were fitted this way. Heat them, they expand; place them over the wheel; they cool, they contract onto it.
[Antegrity]: no, it's not. A rivet cannot be removed by heating and unscrewing it. |
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You could use alloys with different heat capacities.(maybe?) |
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Good idea, but if They had just consulted me during the industrial revolution everything would be built using wing nuts and cotter pins. Nuts would never loosen and one tool would be all you would ever need. |
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Yep, cotter pins and wing nuts. |
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