Mate it may sound odd
but wet them up with the WD
^ You could do the same and heat it. The expansion and contraction can also loosen it.
s
Yes heat is a wonderful tool
and heat and quenching can loosen up things that seen impossible to move
One must be mindful of the materials being worked on
the repercussions can give a result that is expensive.
A commercial hair dryer is handy for general heating.
good for fitting bearings etc
be careful with one of these they can turn a bearing blue in a very short time
When fitting the new nipples make sure to use a good anti-seize on the threads
Lub the seat with a little brake fluid
Bfit