Freeing two metal pieces

[BelleSerene]

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?

 

[cliff]

Plus gas and patience

 

[savageseadog]

Heating is the key. I would douse the area with hot oil

 

[sarabande]

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.

 

[Lady Campanula]

Plus gas and patience

Cliff's the man! Plus Gas frees seized outboards.... What else?

 

[Neil_Y]

ACF-50

 

[JayBee]

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.

 

[BelleSerene]

Many thanks to all for this fabulous advice. PlusGas did the job, and heating helped too.