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In partial answer to Walter Dodson's questions in his recent post, regarding
Bellville washers.

These devices are washers that are "dished" so that in cross section, they
are slightly conical in shape. They come in various thicknesses and spring
rates, and are made of a number of different materials, like spring steel
for instance. When compressed by tightening a bolt, they are essentially a
linear force spring designed to present constant clamping force as they are
flattened.

The idea is to stack the correct number of the correct spring rate Bellville
washers to partially compress at the required bolt torque. As long as they
are properly (partially) compressed, the Bellville washer(s) will maintain
constant clamping forces with expansion and contraction of the bolt and/or
the mating parts. They work as the washer under the head of a bolt with the
added feature of maintaining bolt clamping forces.

These devices have been used in the aerospace arena for quite some time when
joining components that require constant clamping forces and have some
unruly temperature expansion coefficients.

I don't have a URL for the manufacturer but a Web search may turn up the
data. As I remember, the manufacturer makes a wide range of washers, suited
for a wide range of applications.

Dan Schaefer


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Please send your photos and drawings to marvkaye@olsusa.com.
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