[TheForge] Re: Shrink fitting steel to wood

[Mike Spencer]

> Farenheit 6.7x10^-6
> Centigrade 12x10^-6
> Bet Mike was talking centigrade.

Yeah.  Worse than that, I mixed C & F in the calculation.

> ...METALS AND HOW TO WELD THEM... says its 6.5 x 10^-6...
> Any one else know who's right.

Not me. :-) I omitted the minus sign in "10^-6".  You knew that. But I
failed to note that the coeff I looked up was per degree Celsius.
Gak!  I should know better.  13 x 10^-6/deg C is ca. 6.5 x 10^-6/deg
F, just what your source gives.

I *did* use deg F for the estimated 400 deg heat-up.  Since a degree C
is roughly twice as big as a degree F, my number was roughly twice as
big as it should have been.  So a 4" ring would expand diameter only
about 0.005" when heated to 400 deg F.  Doesn't seem like enough to
make much difference in a steel-on-wood application unless you're
*real* fussy about the size of the wood, humidity etc.

Mike Linn says the CTE for low carbon can be twice that for tool steel
and its a SWAG.  For fitting a wagon hub band a SWAG ought to be close
enough. :-)

- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                 						   /V\ 
mspencer@tallships.ca            						  /( )\
http://home.tallships.ca/mspencer/						  ^^-^^

--