Re: Brass screws
Brass is not only to be avoided because of residual ferromagnetism but
is also unsuitable for use in ultrahigh vacuum because zinc has a high vapour
pressure. In an H-maser I used beryllium-copper BeCu for small screws and
springs, aluminium-bronze for larger components and of course pure Al. BeCu
requires special care when being cut as it is toxic, but finished items are
safe to handle when all microscopic swarf and filing "dust" has been removed. I
think magnetic instruments, such as steering compasses, magnetometers etc are
traditionally made of bronze. I have an invaluable but very simple and
sensitive astatic-magnetometer supplied by the Danish Meteorological Institute
in Copenhagen.
John P
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