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| SEM's ... ?? |
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| Bluechip:
Hi Troops .. I know what they are, ie. machine screws with captive washer(s). Used them for donkey's years ... but ... never thought about them much, until earlier today one of the nauseating spotty erks young folk I know asked me what a screw with captive washer was called. I said they are SEM's ... What does that mean ??? from n.s.e .. I don't know :scratch: , a trawl around produced all sorts of stuff, ie. Scanning Electron Microscope etc. Anyone any ideas ?? Apart from taking Laundry Personnel Hostage ... :lol: Dave BC |
| Brass_Machine:
Hmmm... Seems the origin of the name is a but confused: --- Quote ---SEMS A screw and washer assembly. A screw or bolt which has a captive washer. The washer is frequently loose on the plain shank of the fastener, the shank diameter being equal to the effective diameter of the thread; the thread being rolled from this diameter. The origin of the word is a frequent question. In the 1930's E. C. Crowther was a representative for a company that sold both shakeproof washers and screws. He came up with the idea of placing the washer on the screw before it was thread rolled. The major diameter of the screw being larger than the washer hole prevents it from coming off. The Illinois Tool Works made machines that produced these patented pre-asSEMbled washers and screws. The s at the end of SEMs is thought to have been subsequently picked up because they are not usually purchased individually. In spite of the original patents and trademarks the word SEMS is generally recognised as a generic term applicable to screw and washer assemblies. --- End quote --- Eric |
| Bluechip:
Thanks Eric :thumbup: Where did you get that? I spent about half an hour looking, came up with all manner of irrelevant stuff, but missed that one. :scratch: Seems a good account, I'll leave it at that ... life's too short etc.. I suppose it's a comment on my lack of imagination, I've used the things for half a century, it's never occured to me to ponder what the origin was ? Dave BC |
| Brass_Machine:
David, Got it from HERE. Eric |
| snub:
The question of how they get those washers on over the threads has been bothering me for 40 years. So they put the washer on, then form the threads. Oy, that never occurred to me. I learn something new every day! |
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