From: Dave Baker
Subject: Re: How do ya get those crank gears on?!?!
Date: 10 Oct 1998
Newsgroups: rec.autos.makers.vw.aircooled

>From: veeduber@aol.com (Veeduber)

> the expansion coefficient of steel vs bronze and so forth.)

<snip>

If you have the measuring gear to find out the amount of press fit on a
component and want to know the temperature to use here are some simplified
expansion coefficients:

These are in THOU per INCH of size per 100 degrees CENTIGRADE.

Cast iron - 1.2 thou
steel or bronze - 1.7 thou
aluminium - 2.1 thou

All of the above depend on the grade of material, especially aluminium which
can vary a good bit. The exact specs can be looked up in a reference library
(or no doubt on the web).

Example - 3.5 thou fit on a 1.2 inch steel component. That works out to 2.9
thou per inch. 2.9 / 1.7 x 100 = 170 degrees C. (Multiply by 1.8 to get
Fahrenheit of course).

Always use about 20% extra temperature to allow for cooling down during fitting
and transfer of heat to the part being assembled to.

Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work.