Jammed brass thumbscrews in alloy clamps

[Arbian]

I am sure this is a common question (apologies) but I can't spot an answer .... thumbscrews jammed solid and tried grease / brute force / heat from blowtorch but cant get much movement then jams solid again. Grease is being wiped off at clamp surface so not getting into thread. Any tips before brute force and extreme ignorance create broken screw? Screws seem straight and no obvious thread damage.

[headdownarseup]

Get busy with a wire brush on the threads.
Then soak with wd40 or similar for a few days and try again with some heat.(dont be afraid to put some serious heat into this area as the clamps are bronze and will take a fair bit to melt with a plumbers blowtorch)
Slowly but surely you'll start to see movement.
working the screws backwards and forwards should work the corrosion out from the threads.
Re=grease when your done

jon

[Arbian]

Jon, It is the later bracket with the alloy clamps .... same procedure and plenty heat? Cheers Ian

[Charles uk]

Only heat the aluminium, it expands more than brass, then backwards & forwards, the aluminium oxide jamming the threads will slowly work itself out as a white powder.

[Arbian]

Thanks Charles, Will give that a go at the weekend. I just got hold of a 125 on which everything was jammed soild, carb, clamps, gear lever and barrel. I got the carb moving with release oil but it will need a strip and clean and after much soaking in WD40 and a bit of gentle persuasion got the piston freed and the bore cleaned up ok so I am still living in hope!

[headdownarseup]

I had a FNR bracket in similar condition a little while back.
I found heating (gently and not too fierce with the heat) and then quenching/soaking with wd40 or similar will "pull" some of the lubricant down into the seized threads as it cools.
heat and soak/quench a few times and try again. see what happens.
It should free off ok, just dont get heavy handed with it. (keep the hammers locked away)

jon

[Arbian]

Cheers Jon, I will give that a try. Thanks Ian.

[Arbian]

Success ..... with only a minor hiccup ..... got a little heavy handed with one which was not keen to budge and snapped the tab off (no patience). Left that one a few days with a bit more WD40 and after another heat and filing two flats on the broken end got that one moving too. Screwed them both right out and managed to clean the internal threads with a wee wire brush which is meant for cleaning the bore on air rifles which worked rather nicely then a scoosh through with aforementioned release oil and screws went back nice and freely. Cheers for the advice guys, the heating did the trick.