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

Use stainless, preferably 316 and a teflon anti-seize goo.

"CB" wrote in message
ups.com...

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

The stainless is more noble than aluminum, hence the stainless will
corrode the aluminum. But, since the bolt is so small compared to the
mast the damage done by the corrosion will be very, very, very slight
and the damage will not be localized at the hole, but over the entire
volume of the aluminum. At least, that is what I've been told and how
I've done similar work on my mast. Use the goo though.

On 24 May 2007 06:42:50 -0700, Todd wrote stuff
and I replied:

This does not sit well with me. I thought that localisation was why
stainlless screws ended up in powdered aluminium and came loose. The
way I learnt it, the actual corrosion was across the boundary of the
two.

The stainless is more noble than aluminum, hence the stainless will
corrode the aluminum. But, since the bolt is so small compared to the
mast the damage done by the corrosion will be very, very, very slight
and the damage will not be localized at the hole, but over the entire
volume of the aluminum. At least, that is what I've been told and how
I've done similar work on my mast. Use the goo though.

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

On Fri, 25 May 2007 00:14:06 +0800, OldNick
wrote:

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.

Aluminum riv-nuts are easily obtained, easily fitted, and reasonably
replaceable when the time comes. Screw a SS screw into a riv-nut

Brian Whatcott Altus OK

Brian Whatcott wrote:

Aluminum riv-nuts are easily obtained, easily fitted, and reasonably
replaceable when the time comes. Screw a SS screw into a riv-nut

Brian, do you have a link to a source for these riv-nuts? I can't seem
to find them.

Dan "dhapp-at-wmis,net" wrote:
:Brian Whatcott wrote:

: Aluminum riv-nuts are easily obtained, easily fitted, and reasonably
: replaceable when the time comes. Screw a SS screw into a riv-nut

:Brian, do you have a link to a source for these riv-nuts? I can't seem
:to find them.

Mcmaster-Carr sell them. www.mcmaster.com, look for "rivet nut" in
the fastener section.

David Scheidt wrote:
Dan "dhapp-at-wmis,net" wrote:
:Brian Whatcott wrote:

: Aluminum riv-nuts are easily obtained, easily fitted, and reasonably
: replaceable when the time comes. Screw a SS screw into a riv-nut

:Brian, do you have a link to a source for these riv-nuts? I can't seem
:to find them.

Mcmaster-Carr sell them. www.mcmaster.com, look for "rivet nut" in
the fastener section.
THANK YOU!

On Sun, 27 May 2007 20:26:14 -0400, Dan "dhapp-at-wmis,net" wrote:

Brian Whatcott wrote:

Aluminum riv-nuts are easily obtained, easily fitted, and reasonably
replaceable when the time comes. Screw a SS screw into a riv-nut

Brian, do you have a link to a source for these riv-nuts? I can't seem
to find them.

I googled "riv-nut" for 30,000 hits.
I googled "riv-nut supplier" for 3000 hits.
Here is one of them. It has a cross-section diagram to give you the
idea

http://www.cardinalcomponents.com/fasteners.htm

Brian Whatcott Altus OK