Wilsons Sandbox

Hi gang, Here's my two-pence worth on copper washers: There are two types of copper washers in use to stop things leaking. The first as used on our cars which are basically stamped from copper sheet of around 1/16inch thickness. These are annealed before use and work by being deformed by the tightening force, thus filling any voids in the mating surfaces. These can be re-annealed by heating to cherry red and either being left to cool or quenched. At school, more years ago that I admit to , we used to quench copper in a weak solution of acid to take away any oxide layer and leave them bright and shinny. The other type of copper washers, which are referred to as crushable, are made from much thinner sheet material which is then rolled to form a toroidal (dough nut) shape. These are commonly used on modern cars, under the sump nut for instance. They are not soft and are definitely designed to be used once only, although I guess we have all reused them on occasions. Peter Cole.