On 22 May 2007 19:59:46 -0700, CB wrote stuff
and I replied:

I have a serious concern about a machine thread in the relatrively
thin wall of an almmunium mast. Al does not takew threads well, and
then not fine threads, adn then most thin metals a happier with
coarser threads.

Use a reivet if at all possible. Ironically, even self-tappers of
reltatively coarse thread, with large flutes, are better in thin
sections.

Apart from that, use 316 and some sort of insulator. It's worked on
many boats.


I need to tap out a 1/4" hole in my mast to 5/16" 18 (no threads in
there right now) and put a machine screw in there.

I have some options in terms of metal types and there have been a
number of discussions about corrosion and so on with SS in contact
with aluminum and how really useless the isolating compounds are in a
sal****er environment etc etc

So what's the metal of choice? I'm seeing brass, SS, silicon bronze,
zinc plated steel.. what's optimal for the aluminum (non-)interaction?
These other discussions don't have a consistent conclusion. (And no
rivets, this is a small job, I really do need the machine screw).

This is a freshwater boat and has been for a long time. However I
wouldn't rule it out of taking it down the east coast one day.

Thanks for any comments,

-CB