Here we go again - a long newspaper article this -
And so to the technical side, valve production is in three parts - metal components come from the components factory; glass pieces and bulbs from the glass factory and filaments and fine wire from the wire factory. Most fascinating of all was the wire factory where I saw how a tungsten bar two feet long was drawn down and stretched until it was 100 miles long to a thickness of 1/10 that of a single human hair.
But that's not the end of the wonders as the wire was then checked on a super-fine balance which weighs down to 2/100 of a gramme. These incredible dimensions are achieved by passing the wire through diamond dies - between 200 and 250 of them. As the wire passes through each one it is slimmed more and more and each die involves a separate piece of machinery. Each diamond is worth, dependant upon size, somewhere between £2 and £30 with each during it's lifetime fining down about one million miles of wire. To allow passage of the wire through the dies, the diamonds are drilled with a sewing needle coated with a special abrasive.
Part 6 will be coming soon.........