Square holes can be cut with a good drill press and a milling table.
this table can be cranked in both directions while you are using a
milling bit.
These tables are available from the tool companies like Harbor Freight.
They are made overseas and do not have the precision to make watch
parts, but they beat a file and saber saw.
The milling process is hard on the drill press, because they are not
designed for a side load. But, if you do not extend the spindle down
(leverage magnifies the load) and make no more than a few amplifiers a
month, the drill press should be able to stand it.
It is easier to find a friend who owns a machine shop that can do the
whole thing for you on an automated machine while both of you sit there
and sip coffee.
As an aside, I recently had a bet with a fellow ham about who could
receive the first shortwave broadcast stations on a crystal set. I
constructed one using a Johnson Matchbox backwards into a diode and old
1915 earphones. Logged 4 stations - 3 on the 49 meter sw band and one
on 3925. Sensitivity is about 2,000 uv and selectivity is about 200-250
khz. The relevance of this information is that I am still waiting to
hear my first ham station on the crystal set. That should be on 3870
when the converted broadcast transmitters get on am in the early
evening. I am planning on breaking in and telling them I am copying
them on a Johnson Matchbox.
73, Colin K7FM
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