Yeah Hey PETER, don't do the LYE bath treatment while driving to work...
Yes you also hit the nail on the head, HELICOILS are all the rage for strong
threads mounted in aluminum. But you need depth no matter what with them.
The only strong amp stuff I've seen with bolts into aluminum were my Collins
208's and if any of us are building like that, they are way to cool to be
hanging around here.
BOB DD
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Peter Chadwick
Sent: Tuesday, April 10, 2007 3:02 PM
To: amps@contesting.com
Subject: [Amps] RE : amp hardware
I've gotten somewhat cynical (what me? never! - before GM3SEK says it!)
about tapping holes in aluminium unless there's plenty of thread depth
available. Another problem is using the wrong thread, and by far the 'most
wrong' is metric - ISO metric coarse is far too fine a thread for aluminium
and the like. For larger threads, use UNC, and for smaller threads, the UNC
sizes below 10-28, i.e. 8-32, 6-32 etc. Metric threads are far too fine:
BSF is too, and BSW is a good alternative, al;though it only goes down to
1/8 inch or abour 6-32. Or use the steel coil thread inserts so you can use
metric, with all the cost and fuss of those.....The smaller sizes of BA
trhead are just about OK if you don't need too much torque, they being much
stronger, size for size, than metric - or ANC for that matter. Soft
materials, such as aluminium and copper are absolute b*&^%$s to tap, and
need lubricant and much care. Plus, ideally, access to a spark erosion
machine to remove broken taps....suc
h access, by Murp[hy's Law, reduces the chances of tap breakage enormously.
But the caustic soda treatment I've used quite succesfully. Sure, you need
to be careful because it has its dangers. So does dfriving to work.......and
just look at the idiots you see on the road who manage that succesfully!
73
Peter G3RZP
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