Physics lesson required!

[offshore]

First to admit to paying little attention during my physics classes all those years ago!

So can some one tell me, if I apply heat to a bezel ring ( I am trying to install a new bezel insert on a 6138-0040 Seiko) will the expansion with heat, make the inner circumference, greater or less?

Whilst I understand that the outer would increase, what takes place on an inner circumference?

The new bezel insert, has a lip which needs to seat under a corresponding lip in the ring, and it is just a "poofteenth" away from seating, but no amount of press seems to want to allow it to seat.

I know I could sand a little off the insert, and glue it, but would like to be as "original" as is possible.

The old bezel ring appears good as far as being true in round, and I have cleaned back some furry edges which may be preventing the insert going in, but it just won't seat.

Physics majors required here please!

Offshore

[smc]

If it was a pipe, the inside diameter woud expand as well...

In theory the same should happen to a bezel ring - HOWEVER - it's pretty thin and it's an unstable shape. I would think that heat could easily cause warping. Heat it slowly and evenly, maybe by putting it in a pot of cold water on the stove, and bringing it up to a boil? When at temperature, I would also not force it at all to avoid creasing.

But what the heck do I know LOL.

[Ronin]

Heat will cause expansion.

You might want to chill the case in the fridge/freezer, and warm the bezel (or room temp -vs- cold case). It should come together flawlessly.

-Ronin

[drhydro]

Ronin's right- heat causes expansion. Both the inside and outside diameter of something like a bezel ring will increase when heated. (And, conversely, decrease when cooled.)

Diameter after heating = diameter before heating X (1 + (coefficient of expansion) X (change in temperature) X (diameter before heating)).

Coefficient of expansion for stainless steel is about .000011 inch per inch per deg Celsius.

If ya had a bezel with an ID of 38 mm, heating it 100 deg C would increase its diameter to about 38.04 mm. Not much, but maybe enough to make the difference. I wouldn't heat it much more than that- and you have to be quick! And wear gloves.

Edit:

Aluminum's coefficient is about twice that. And the exact numbers vary, depending on the alloy. So YMMV.

[offshore]

Thank you gentlemen!

So I put the bezel ring in the sun here today, (about 30-33C room temp- maybe ?40C in the sun) and then placed the insert on and put it in my press.

Voila, in it went!

So the inside circumference, certainly increased, as did the outside.

It had been previously difficult to repress on the crystal/case as well.....another sunbathe, and on it went. (Bigger inside circumference again!)

Ahhh the joys of watch repair.....and the things we learn on the way.

Offshore.