Exhaust flange nuts


aviationeyes
 

A couple years ago I overhauled my exhaust system and replaced the exhaust flange fastening hardware. I had noticed during dis-assembly that I had a mix of nuts on the flanges. Some were badly corroded and some looked perfect. The ones that were perfect were easier to remove and turned out to be stainless steel. During re-assembly, I re-used the stainless steel nuts and used brand new Lycoming plain steal nuts.

The plain steal nuts are now rusting badly and will be a pain for service. I believe the Vetterman exhaust kits use SS nuts. I asked them what alloy nuts they use, 304, 316, 324, and if they would sell me some nuts but no response. Aircraft Spruce now sells 324 studs, but no SS nuts specific to the application.

What stainless steel nuts are enlightened people using?

--Jose




David A Froble
 

On 9/26/2021 11:39 AM, aviationeyes wrote:
A couple years ago I overhauled my exhaust system and replaced the
exhaust flange fastening hardware. I had noticed during dis-assembly
that I had a mix of nuts on the flanges. Some were badly corroded and
some looked perfect. The ones that were perfect were easier to remove
and turned out to be stainless steel. During re-assembly, I re-used the
stainless steel nuts and used brand new Lycoming plain steal nuts.

The plain steal nuts are now rusting badly and will be a pain for
service. I believe the Vetterman exhaust kits use SS nuts. I asked them
what alloy nuts they use, 304, 316, 324, and if they would sell me some
nuts but no response. Aircraft Spruce now sells 324 studs, but no SS
nuts specific to the application.

What stainless steel nuts are enlightened people using?

Don't know who might be "enlightened", however a few minutes on the computer/internet gives a bit of information.

304 tolerates higher heat than 316

316 includes molybdenum, grade 316 stainless steel is more corrosion resistant than similar alloys, such as 304 stainless steel, when exposed to corrosive chemicals

Frankly, just about any SS will be much more corrosion resistant then steel, therefore, I'd suggest concentrating on what you can get.

Don't count on Aircraft Spruce for everything, they are a good resource, but not the only one. Lots of sources for SS hardware. Doesn't have to be an aviation source. SS is still SS, no matter who is selling it.

If you want to experiment, purchase several grades of SS nuts, document which are used where, and if some out perform others, replace the lesser performers in the future. Or just replace all of them periodically.

As for me, I'd start with the 304, for heat tolerance.

--
David Froble Tel: 724-529-0450
Dave Froble Enterprises, Inc. E-Mail: davef@...
DFE Ultralights, Inc.
170 Grimplin Road
Vanderbilt, PA 15486


aviationeyes
 

David, thanks for,your comments. Your perspective is right that any 300 series SS would be better than the Lycoming std steel nuts. I guess I'll just try the 304 from McMaster Carr.
--Jose

On Sun, Sep 26, 2021, at 11:57 AM, David A Froble wrote:
On 9/26/2021 11:39 AM, aviationeyes wrote:
A couple years ago I overhauled my exhaust system and replaced the
exhaust flange fastening hardware. I had noticed during dis-assembly
that I had a mix of nuts on the flanges. Some were badly corroded and
some looked perfect. The ones that were perfect were easier to remove
and turned out to be stainless steel. During re-assembly, I re-used the
stainless steel nuts and used brand new Lycoming plain steal nuts.

The plain steal nuts are now rusting badly and will be a pain for
service. I believe the Vetterman exhaust kits use SS nuts. I asked them
what alloy nuts they use, 304, 316, 324, and if they would sell me some
nuts but no response. Aircraft Spruce now sells 324 studs, but no SS
nuts specific to the application.

What stainless steel nuts are enlightened people using?

Don't know who might be "enlightened", however a few minutes on the
computer/internet gives a bit of information.

304 tolerates higher heat than 316

316 includes molybdenum, grade 316 stainless steel is more corrosion
resistant than similar alloys, such as 304 stainless steel, when exposed
to corrosive chemicals

Frankly, just about any SS will be much more corrosion resistant then
steel, therefore, I'd suggest concentrating on what you can get.

Don't count on Aircraft Spruce for everything, they are a good resource,
but not the only one. Lots of sources for SS hardware. Doesn't have to
be an aviation source. SS is still SS, no matter who is selling it.

If you want to experiment, purchase several grades of SS nuts, document
which are used where, and if some out perform others, replace the lesser
performers in the future. Or just replace all of them periodically.

As for me, I'd start with the 304, for heat tolerance.

--
David Froble Tel: 724-529-0450
Dave Froble Enterprises, Inc. E-Mail: davef@...
DFE Ultralights, Inc.
170 Grimplin Road
Vanderbilt, PA 15486


--

skyeyecorp@...


Jim Evans
 

Might not be a good idea using stainless on stainless.  Threads tend to gawl when trying to disassemble. Generally would use a good grade of antiseaze but on exhaust may be futle. Folks here of higher intelligence may contradict this and would like to hear the arguments.


On Sun, Sep 26, 2021, 11:37 aviationeyes <skyeyecorp@...> wrote:
A couple years ago I overhauled my exhaust system and replaced the exhaust flange fastening hardware. I had noticed during dis-assembly that I had a mix of nuts on the flanges. Some were badly corroded and some looked perfect. The ones that were perfect were easier to remove and turned out to be stainless steel. During re-assembly, I re-used the stainless steel nuts and used brand new Lycoming plain steal nuts.

The plain steal nuts are now rusting badly and will be a pain for service. I believe the Vetterman exhaust kits use SS nuts. I asked them what alloy nuts they use, 304, 316, 324, and if they would sell me some nuts but no response. Aircraft Spruce now sells 324 studs, but no SS nuts specific to the application.

What stainless steel nuts are enlightened people using?

--Jose




johntoelaer
 

I used brass nuts rethreaded to coarse thread
n138ez