Expansion in an isotropic media such as most metals is the same in all
directions. Think of enlarging something for printing by a fraction of
a percent.
Everything gets larger by the coefficient of expansion/deg C. Thus,
holes get larger, OD's get larger, and circumference the same as
Diameter * pi. A shrink fit only needs to consider the radial
interference that is desired.
The 0.00034" change in the radial gap I calculated for 100 deg C
temperature change is meaningless if the two parts were slipped together
by hand. It doesn't matter in this case whether the inside part has a
higher coefficient of expansion or not, since the gap machined as was
described was certainly several thousandth of an inch.
Extruded tubing is not round and welded pipe/tubing is even more out of
round, which is probably why the machining was needed.
Grant KZ1W
On 10/4/2021 11:21, David Gilbert wrote:
I'm not sure that percentage of expansion is the relevant consideration
here. I would think that the gap between the cylinders (i.e., portion
of the diameter) is the important part, and since the expansion occurs
in the circumference the gap changes by a factor of pi less.
Even less reason to be concerned, I think.
73,
Dave AB7E
On 10/4/2021 8:00 AM, Lux, Jim wrote:
Circumference and diameter grow by the same percentage (since C = d *
pi), so CTE wise, it's the same whether you use diameter or
circumference.
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