Hi all,
I’m mostly a flute player & uilleann piper…my whistles/low whistles don’t get played much these days. However, I have a few gigs to do for St. Patrick’s Day where I’ll be playing with a singer who likes to do the occasional number in F or Bb. I got out my Phil Hardie F low whistle the other day and the tuning slide was quite thoroughly stuck. No amount of agonized twisting could get it to budge…Any suggestions on how I can get it un-stuck?
What material is it made out of?
One technique I’ve used with a composite whistle was to put it in the freezer for a short time and then twist it. It worked for me. My guess is that the cold causes contraction, but that the two parts contract at a different rate which causes the parts to release their death grip on each other.
My Kerry Songbird low D became stuck shortly after getting it.
I wrote to Phil but ended up doing my own thing. I agonised prior
to placing the whistle in a vice, using lots of protective wrapping
around it first. I was then able to twist it free without too much
force.
I cleaned up the slide surfaces and used petroleum jelly as the
lubricant as it is much thinnerand does not grab and lock the slide.
It has been fine ever since.
It’s aluminum, right?
Put it in the freezer as someone else suggested. Get your tap water running as hot as possible then run the water over just the outside female part of the slide. The cold will induce shrinkage in the male, 
while the warmth will expand the female part and it should come apart.