Banjo washers

ashman said:

I will just get my 5 string banjo out and play a tune, does that count lol.

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JimNH said:

Annealing aluminum is tricky without a controlled temp oven as it doesn't change color but simply melts if you get it too hot. Yes for some reason Sharpie just disappears (burns off?) at a temperature high enough to anneal. It's only good for something like a crush washer that's been strain hardened by use and you want to use it again. It'll be soft and then again strain harden when used. It's not for something like 2024 T3 which will anneal to O but would have to be properly heat treated back and that requires some precision and an oven. Aircraft 2024 parts are often made in the O state then sent out for heat treating. You can also I'm told but haven't tried, smoke/soot the part with an acetylene flame then heat carefully until it burns off.

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JimNH said:

I didn't know than copper didn't care how cooled. As a young aircraft mechanic we'd accumulate hundreds of copper spark plug washers as spark plugs were often cleaned of the lead deposits. We'd then anneal them in huge batches on a piece of welding wire and quench. The oil would burn off and quenching would leave them nice and clean.
At some point the FAA mechanics guide removed the annealing statement and now says to use a new washer. It also used to say to wash parts in avgas.
Back in the day there were three common avgas types - 80/87 for low compression engines, 100/130 for higher, and 115/145 for mostly military high performance radials. All of the blends except the 80/87 had way more lead than today's 100LL which still has plenty. We contracted with the Army who for some reason was using 115/145 in their planes and had an order to run full rich below 5000' feet. Often even with a vibrator we couldn't get the lead out of their plugs and would have to scrap them.
The dual anti-knock rating i,e, 100/130, is a lean/rich rating that somehow disappeared with 100LL.
There, why I used to anneal copper

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dobba99 said:

Annealing Aluminium is easy, rub the part with soap and heat until the soap turns black, dunk in water. Job dun

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ashman said:

On my Triumph Thruxtons they had alloy drain plugs washers, never had to anneal them and they never leaked, when I replace the oil filter they threw in a new drain plug washer every time, same as my copper drain plug washers have never anneal them they are soft enough.

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robs ss said:

I recall an experiment in the material lab at college some 47 year ago (shit! That long?) where the lab assistant put a piece of copper (1" dia and about 2" long) in a large hydraulic press and asked us to predict what would happen.
The copper bar squashed to a barrel shape then stopped deforming as the pressure continued to rise.
Nothing, nothing, nothing... then BANG! it exploded.
We were protected by the safety cage around the piece.
We examined the exploded pieces and all looked like shattered glass. Very shiny and very sharp.
So, the copper went from relatively soft and pliable to hard and very brittle only by being work hardened by one cycle. Yes, and extreme cycle, but...
Iron, stelel and aluminium will not exhibit this behaviour.

So... look after your copper washers!
Cheers

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