[TheForge] shrink fit techniques

Fri Feb 1 11:11:01 2002

Reliable heating requires heating the whole part or assembly uniformly. 
Example: Shrink fitting a coupling onto motor shaft. You put the coupling in
an oven and heat it up uniformly, and slip it on before: a) the shaft heats
up or b) the coupling cools off

With practice rosebuds could be used, or induction heating coils. But the
tolerances are tight, in the range of thousandsth of an inch. A .001 or .002
shrink fit is TIGHT!!! Especially with larger the diameters.
OF course large is relative.

For some working on steam turbine shafts of 22" diameter is large, for
others, 1" is large. (Diameter!!  ;-))

Rule of thumb:
Steel will expand .001" per inch of thickness per 100 degree rise in
temperature.

-----Original Message-----
From: Doug Ayen [mailto:[email protected]]
Sent: Friday, February 01, 2002 10:48 AM
To: [email protected]
Subject: Re: [TheForge] shrink fit techniques

"Miller, Ray (GEAE)" sang:
> 
> My experience with shrink fits is in steam and gas turbine assembly
> techniques. 
> In my experience the practice was always, make the dowel bigger than the
> hole, depending on the shrink fit desired, and then shrink the dowel with
> dry ice in a zylene bath and slip the dowel in before it warms back up.
Once
> its in, its in, and any errors require drilling.
> 
> Heating a hole to expand it never works reliably, because if you are not
> careful where you start heating, you will actually shrink the hole.
> 
> Ray Miller
> Cincinnati
> 

So, how *do* you heat it properly to get a good fit? Or is the cold method
the only method that is reliable?

--doug
_______________________________________________
http://mailman.qth.net/mailman/listinfo/theforge
theforge mail list group photo site is
http://www.photoaccess.com
Login:  [email protected]
password:  anvil
___________