Freeing two metal pieces

BelleSerene

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19 Sep 2005
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I left my sextant, one of these Astra 3B jobs, on the boat for many months. The micrometer drum has a brass cylinder with the worm screw on the end, rotating inside a steel part. Except that these two have corroded together so the drum won't rotate. Even using pliers.

The very knowledgeable Mr Robinson of Robinson's Compass Adjusters in Hamble (swung my compasses and also trades in rather cuter sextants including some very reasonable Soviet ones which I'd have bought instead had I known) had a look and recommended immersing that part of the mechanism in paraffin to free it. I did and it didn't.

I'm keen to use the sextant on a N Sea passage in a couple of weeks' time, but it's beyond my wits to get these two parts moving again. Can anyone with some mechanical or metallurgical knowledge advise me?
 

sarabande

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6 May 2005
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heating and allowing to cool, then repeat, as the two metals have dissimilar co-efficients of thermal expansion; this should break the bond and suck oil into the threads/spindle.
 

JayBee

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15 Sep 2004
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Bill Morris is your man. You can contact him through his website:
http://sextantbook.com/.

The website publicises his book and blog, but he will probably be pleased to give you the best advice for fixing your problem -free.
 
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