[modeleng] Re: Technical education
- From: "alan stepney" <alan@xxxxxxxxxxxxxxxx>
- To: <modeleng@xxxxxxxxxxxxx>
- Date: Sat, 5 Aug 2006 19:11:53 +0100
John,
I knew I had it somewhere, but will come onto that.
If the thicker nut is screwed down onto the thin nut "to within a few
degrees of its limit", I doubt that the lower nut COULD be undone. However,
that depends on how one defines "tightened in normal way" and all the othe
terms used.
Now, moving on, the hoary old topic of thin nut at top or bottom keeps
coming up, in ME, EIM, and almost everywhere else.(And this is what I was
looking for.)
ME for 17 March 1995 carried an article by Tubal Cain, in which he traced
the origins of the thin-nut-at-the-bottom idea to Manual of Machine Drawing
& Design, in 1893, and reprinted continuously thereafter, and that
information being repeated in other later publications.
He then goes on to dismiss that idea, with proofs to show its fallacy.
My own view is that for anyone making a model of an early machine should
stick to the thin at top, as that was the way it was usually done, way back.
Of course, today with nuts tightened to torques that deliberately stretch
the studs / bolts, it has moved into an entirely different field.
I still feel that the statment in that book is so loose to be worthless, and
the information, which is stated as fact, far too liable to
misinterpretation, plus, if TC was right, and he usually was, incorrect.
Alan
----- Original Message -----
From: "John Pagett" <john_pagett@xxxxxxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Tuesday, August 01, 2006 9:18 PM
Subject: [modeleng] Re: Technical education
Alan,
Well I'm going to stick my head above the parapet.
This is what I think the guy's going on about. The thin nut is tightened,
stretching the bolt slightly and making the upper flanks of the nut thread
bear against the lower flanks of the bolt.
The other nut is bought down to bear against the lower nut, but not tightly.
Again the upper flanks of the nut thread bear against the lower flanks of
the bolt thread.
By "loosening" the lower nut, the clearance in the thread is taken up in the
opposite direction, so now the lower flanks of the nut thread push against
the upper flanks of the bolt thread. In the meantime the clamping load has
been transferred to the upper nut threads. The tension in the bolt should
remain the same.
As to whether he's right.... I dunno.
As those who remember leisurely Saturday afternoos with Kent Walton's
measured wrestling commentaries might recall
Seconds away, round one
JohnP
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