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PostPosted: Sat Apr 17, 2010 7:08 pm 
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Joined: Fri Feb 12, 2010 12:57 am
Posts: 85
Location: Ashby de la Zouch
We've all been there - half way through an oil & filter change when we realise we forgot to buy a new sump plug washer. Do we re-use the existing washer? Well, you can, and it's quick, cheap & easy!

Copper (Cu) and Aluminium (Al) are used for washers because they are soft, and when you tighten up your sump plug, the metal washer material deforms to match both surfaces, resulting in a nice tight seal. Unfortunately after being used once, they start to harden meaning next time you try to use them they will not seal as well.

Metals have a crystalline structure, being made up of thousands of tiny crystal grains, and much of their inherent hardness is actually due to the boundaries between these grains. "Working" a metal (i.e. by tightening your sump plug) will split some of the grains, resulting in an increase in the number of grain boundaries, and hence harden the metal. Conveniently, all we do to reduce the number of grain boundaries is heat up the metal and allow the grains to grow again - this process is called annealing. The trick is knowing just how hot to get them, and this is different for Cu and Al:

Cu:
  • Take the washer (cleaned) and 2 pairs of long nosed pliers.
  • Holding the washer with one set of pliers, heat it over a gas burner (like your kitchen hob or a camping stove, but not a cigarette lighter) until it starts to glow a dull red colour. If it gets hotter than that, it'll glow with a cherry red colour, and that's fine, but don't get it much hotter because it'll melt.
  • Now pass the washer into the second set of pliers, holding it by the other side and heat it again, so that the part of the washer that was underneath the first set of pliers gets hot this time.
  • Allow the washer to cool at it's own rate - don't quench it in water
  • Clean off any deposits of soot with some fine emery paper.

Al:
  • Take the washer (cleaned) and 2 pairs of long nosed pliers.
  • Hold the washer over a burning candle until it's covered in soot.
  • Holding the washer with one set of pliers, heat it over a gas burner until the soot burns off.
  • Now pass the washer into the second set of pliers, holding it by the other side and heat it again, so that the part of the washer that was underneath the first set of pliers gets hot this time.
  • Allow the washer to cool at it's own rate - don't quench it in water
  • Clean off any deposits of soot with some fine emery paper.

That's it! You may now re-use the washer, with the smug satisfaction that you could have saved as much as £0.03 - every little helps.

Disclaimer: If you decide to try this technique, don't come crying to me if you burn yourself or leave a washer-shaped mark on your kitchen worktop - things that are heated get hot, and things that are heated until they glow red get very hot, but you already know this and so it's your own stupid fault and you probably deserve all the grief that your other half will bestow upon you.

Fozberry

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PostPosted: Sun Jun 06, 2010 1:08 am 
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Joined: Fri Feb 05, 2010 9:04 pm
Posts: 16
Location: Kent - The Garden of England
Great tip..... Thanks


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PostPosted: Wed Jun 23, 2010 10:55 pm 
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I'd rather race a Honda 90

Joined: Fri May 08, 2009 8:31 am
Posts: 3493
Location: Rhodesia.
From annealing position.... ;)

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Spencer Racing... www.spencerracing.co.uk


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