My SB-220 has a lot of American-style coarse metal tapping screws to hold
on the top cover, but it also has some special little press-in fixtures
under the front edge of the chassis - I believe these are actually some
sort of fixed nut, but don't know what the nomenclature is. Anyway,
another option.
73, Pete N4ZR
At 04:43 PM 4/10/2007, Robert Bonner wrote:
>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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