Hot or cold for expansion ?
 

I'm making a 50mm long aluminium sleeve for a 12mm steel shaft; it is
just a support sleeve, no rotary motion. I've reamed the Al. out to
the 12mm required and tried fitting the steel shaft. It went in fine,
but I suspect it's picked up a little flake of the Al as I went to
withdraw it and has stuck fast.

Do I heat it to assist removal or deep-freeze it ?

The second bush is fine with the same reamer setting, but I made sure
there was no debris lying around on the trial fit with an identical
bit of steel.

Thanks
Rob

Hot or cold for expansion ?
 

On Sun, 16 May 2010 06:04:18 -0700 (PDT), robgraham wrote:

Do I heat it to assist removal or deep-freeze it ?

Google is your friend:

"coefficient of expansion metal*"

First hit:

http://en.wikipedia.org/wiki/Coeffic...rmal_expansion

I'll leave the drawing of the answer as a excercise for the OP.

--
Cheers
Dave.

Hot or cold for expansion ?
 

"robgraham" wrote in message ...
I'm making a 50mm long aluminium sleeve for a 12mm steel shaft; it is
just a support sleeve, no rotary motion. I've reamed the Al. out to
the 12mm required and tried fitting the steel shaft. It went in fine,
but I suspect it's picked up a little flake of the Al as I went to
withdraw it and has stuck fast.

Do I heat it to assist removal or deep-freeze it ?

The second bush is fine with the same reamer setting, but I made sure
there was no debris lying around on the trial fit with an identical
bit of steel.

Thanks
Rob
http://www.engineeringtoolbox.com/li...ents-d_95.html

Looks like aluminium expands twice as much as steel, and as the ally
is on the outside, you need to heat it.

--
Graham.

%Profound_observation%

Hot or cold for expansion ?
 

On 16/05/2010 14:04, robgraham wrote:
I'm making a 50mm long aluminium sleeve for a 12mm steel shaft; it is
just a support sleeve, no rotary motion. I've reamed the Al. out to
the 12mm required and tried fitting the steel shaft. It went in fine,
but I suspect it's picked up a little flake of the Al as I went to
withdraw it and has stuck fast.

Do I heat it to assist removal or deep-freeze it ?

The second bush is fine with the same reamer setting, but I made sure
there was no debris lying around on the trial fit with an identical
bit of steel.

Thanks
Rob

Don't forget that bimetallic corrosion may occur especially in damp/wet
conditions, the results may cause the two metals to corrode and seize up.

Don

Hot or cold for expansion ?
 

Unless you've got CO2 or N2 freezing gear, you're only going to get a
20 degree difference by cooling.

With boiling water, hot air gun, or a blowtorch - you can easily get
much larger temp differences.

Hot or cold for expansion ?
 

On 16 May, 18:19, " wrote:
Unless you've got CO2 or N2 freezing gear, you're only going to get a
20 degree difference by cooling.

With boiling water, hot air gun, or a blowtorch - you can easily get
much larger temp differences.

Thanks guys - I'm afraid the quick answer was I just took a biggish
punch and drove it out. And yes, there was Al smeared on the steel
and had to be file off.

I suppose I should have remembered that Al has the larger Cf of
Expansion and just plunged it into some boiling water.

Rob