Annealing auto plug washers?

Steve Sampson · #1 10-12-2008, 06:05 AM

With conventional aircraft plugs it is normal to anneal the washers before reinstalling.

With my P-mags I have auto plugs. What is normal procedure with these? They don't look as though they are made of copper. I don't plan to reuse them many times, but a 35 hour check appears to be appropriate.

thanks

osxuser · #2 10-12-2008, 07:20 AM

If you can get new ones, that works, if not, I think Aircraft spruce sells 14mm copper gaskets.

Bob Brown · #3 10-12-2008, 10:01 AM

That brings up a good point, would there be an upside or downside to going to a 14mm copper washer here? The one the comes on an auto plug is normally crushed on the first install...I think you could re-use it, if you retorque it, but would it just be better to replace these with copper??

rv72004 · #4 10-12-2008, 10:31 AM

Heat the copper plug washer till its red hot and then let it cool naturally. This will soften the copper and allow a proper seat/ seal when refitting plugs. I also use a bit of thread lube when reinstalling.

tommylewis · #5 10-12-2008, 06:49 PM

My IA aways anneals the copper spark plug washers by heating red hot with a torch and then dropping them in cold water. I have aways followed this practice on my C182's plugs.

On my RV7a, I have dual PMAGs and use the recommended auto spark plugs. When I take them out, I replace them with new plugs. The last set I ran 135 hours on before replacing. I will probably replace them every 100 hours in the future. After all, they are only $2 per plug times 8 plugs is $16 total.

Just my opinion.

Little_Richard · #6 10-12-2008, 08:09 PM

Auto plugs are too cheap to mess with. It is probably best to just replace them.

Mel · #7 10-12-2008, 08:23 PM

To anneal washers they should be heated and allowed to cool slowly. Quenching them in cold water will make them brittle, not soft.

RVadmirer · #8 10-12-2008, 08:52 PM

...natural cooling keeps them soft, quenching makes them hard. Google it and you'll see what my A&P explained, as did Mel. Nothing wrong with reusing good washers but then some folks feel differently about economy and confuse it with unsafe practices. Not alway the case. Why waste when tried and true methods give economical results? Little things add up, but then maybe your portfolio is still looking terrific.....!

chaskuss · #9 10-13-2008, 09:08 AM

Quote:

Originally Posted by Mel

To anneal washers they should be heated and allowed to cool slowly. Quenching them in cold water will make them brittle, not soft.

Mel,
I have to ask you why quenching them in water is bad?. I learned this method (water quenching) 30 years ago from a Triumph motorcycle repair manual. It does not make them brittle in my experience. What is the disadvantage of water quenching?
I have found it advantageous to anneal all copper washers or head gaskets (motorcycles) prior to use. These parts get work hardened at the edges, during their manufacture.
Charlie Kuss

Mel · #10 10-13-2008, 09:36 AM

The purpose of annealing the washers is to soften them so that they will "crush" and seal. If you quench them in cold water the material will become more brittle and may not seal properly.
Take 2 pieces of steel. Heat them both. Allow one to cool slowly and quench the other one. Put them both in a vise and bend them. You will find that the annealed one, the one that cooled slowly, will bend much further than the quenched one before breaking.