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Old May 17th 06, 02:55 PM posted to rec.radio.amateur.antenna
Gene Fuller
 
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Default mechanical question, aluminum swaged joints

Dave wrote:
diameter tolerance is what i am looking for. this is an antenna element
joint with 2 through bolts in the swaged area, no slitting. measured
diameters are 1.252 OD for the inner piece and 1.264-1.277" ID for the
swaged section, slightly out of round because of the 2 bolts flattening it a
bit. the bolts are vertical and when tightened 'normally' which causes a
bit of flattening, the element can move horizontally quite a bit. any
recommendations for improvements?? adding horizontal bolts? shims? any
portable tools to swage something that big, or is that a machine shop only
type of job?


Dave,

The easiest fix would be to add one or two more bolts in the horizontal
direction. The resulting shape of the outer element would be slightly
squared, but that should not cause any problems. Thin shims would be a
nuisance.

There are portable tools used for swaging. In particular, people who
make boilers for model steam locomotives often use a swaging process to
fit the boiler tubes tightly into the end plates. The key for any sort
of portable or hand-held swaging is that it is much easier to expand the
smaller tube than to shrink the larger tube. The metal needs to be soft,
however, and useful aluminum antenna elements would generally be a bit
hard. Since you need only a few mils, it might work.

73,
Gene
W4SZ