On Jul 5, 7:12*am, riverman wrote:
On Jul 5, 12:01*pm, rw wrote:



On 7/4/10 9:38 PM, george9219 wrote:

On Jul 4, 1:02 pm, *wrote:
On 7/4/10 10:41 AM, riverman wrote:

However, the female end is less clear. Think of a donut (as the female
end of a ferrule resembles a donut in cross-section): first instincts
may say to heat the female end to expand it, but when a donut expands,
the hole actually gets smaller. SO heating the female end may make the
ferrule tighter.

I'm afraid that you're wrong. Heating the female ferrule will cause the
hole to expand. So it's best to heat the female ferrule and cool the
male ferrule.

--
Cut "to the chase" for my email address.

What RW said. Heat the female ferrule. The wall section of the female
has less mass and will expand faster than the male section.

The donut analogy is misleading. A cooking donut doesn't expand like a
"normal" material undergoing classic thermal expansion. A better analogy
is that the cross section of the ferrule would expand like a
photographic enlargement, in all directions, hole and all. That's why
mechanics sometimes use a torch to free a stuck nut. (I wouldn't use a
torch on a ferrule, but I'd use a XC ski waxing iron, carefully. You're
in Sweden, right?)

In any case, I wouldn't hold much hope for the thermal method of getting
the ferrules apart, although it's worth a try. Brute force is the
answer, I think, and if you aren't strong enough you need to find a way
to get mechanical advantage (or more hands to help).

BTW, riverman, is this a real problem you're facing or is it a quiz
question?

--
Cut "to the chase" for my email address.

It's mostly a quiz question, generated at the end of a string of
musings while casting. I dipped my travel rod in the icy water while
fishing, then noticed a short while later that the ferrule had
loosened, maybe (or maybe not) because of the immersion. So I jammed
the ferrules tightly together, however, when I tried to disassemble
the rod later, it was jammed. Although I was able to get the sections
apart using the 'behind the knee' method, I wondered about the role of
cold water immersion, and the effect on the seated ferrules and when
the rod warmed up. So I started thinking about what role hot or cold
water would have on each section.

The male section is easy....it should contract with cold water, even
if just a little. But the question began nagging me about the action
of the female section. Specifically, would cold water expand or
decrease the radius of the hole, and if it decreased it, would it
decrease less then the decrease of the male section (effectively
loosening the ferrules).

I'm not convinced that heat expands the radius of the hole, as in a
photographic enlargement. Objects expand around their physical mass.
There is a classic physics demonstration with a steel ring and a steel
ball where you heat the ring and find that the ball will not fit
through the ring. So, just as the hole in a rising donut (or bagel is
more like it) gets smaller, I would expect the hole to get smaller if
you heated the female section. But countereffecting that would be that
the circumference of the torus would also increase. Maybe there is
some sort of ratio of circumference to torus thickness where the hole
actually does not change....I don't know. But the action of the female
end of a ferrule is a very thought-provoking thing.

--riverman

The hole expands. I hope you're not a physics teacher;-) Many years
ago, I was involved in the production of M-14 rifles. In order to
prevent corrosion and limit wear, a Stellite liner was permanently
inserted at the breech end of the barrel. The OD of the liner was an
interference fit (about .0002" larger, IIRC) with the ID of the
barrel. To accomplish the assembly, the liners were kept in a bucket
of dry ice, while the barrel was held in a fixture with an induction
coil surrounding the breech end. There were witness marks on the
barrel and liner, so the rifling would line up after assembly. The
induction coil would be turned on for a short period of time, (I don't
remember exactly how long), the liner would be picked up with tongs,
inserted into the barrel, and turned to line up the witness marks.
When the induction coil was turned off, there would be a audible
"click" as the ID of the barrel shrunk. The liners never moved after
that, even when the rifle was fired repeatedly on rapid fire.