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.
In the components factory, cathodes are cut, trimmed and shaped and one automatic machine was capable of reeling off 2500 cathodes per hour and when one considers that only one or two are needed per valve, this level of production represents a lot of valves.
At the end of each bench I noticed a squared sheet headed ‘Quality Control Chart’ where defects can be recorded every fifteen minutes. This scrutiny in the search for the ideal, I found, was the forte of the entire works with 100 people in the factory doing nothing else but inspect the product in its many stages.
One process which proved interesting was the insulation of filament from cathode by coating the spiral tungsten wire with aluminium oxide then a neat gadget gets hold of this much travelled wire and bends it into either an M or V shape. This may seem very complicated but I watched a deaf and dumb boy manipulating one of these machines. He had been taught by a charge-hand purely by demonstration. The wire in this particular machine was cut off at the right length, dropped down into a slot, pushed up into rollers and formed into shape. Then along came a steel hand to hang it on what can best be described as a miniature clothes line.
A partition separated the cathode section from the plant where welding was in operation. Here, anodes were in production with two halves being welded together to form a shape like a miniature fire screen.
While an operator kept a keen eye on all the parts as they moved lifelike, the four slide machine with its many pairs of hands did nine jobs at the same time. The outcome of its activity were a tumbling mass of a minutely shaped things – like a metal snowflake of wonderful design – at the rate of 8000 an hour – beautiful anodes!
In the Grid Department, the grid backbones were being fed through a machine from reels and the tungsten wire, fitted on to a spool was wound around these backbones. The grids, up to now all bound together in one continuous strip, were later cut into single units and connections welded to them in readiness for assembly in the valve base.
The next part of the tour included the Glass Factory where I wished I had discarded my scarf as the furnaces were blazing away at 1200 degrees Centigrade. From the furnaces emerged glass tubing of varying diameter which was fed vertically in an unending cylindrical shape up through two floors to the cutting machines.
After seeing the tubes disappear through the “grill room’ ceiling we then followed them to a part of the factory where the traditional art of glass blowing by power of lungs and skill of eye was neither welcome nor respected. Indeed, I should have pitied the consciencious craftsman who would have the awesome task of keeping pace with the relentless flow of tube from the furnaces below.
Two methods of cutting the tube were in use with the first using a thin band of heat and a cold wheel to effect a break which was then smoothed by application of a flame. A mechanical pair of hands sealed off the end and heated air blew it into the desired size and shape. The second saw a diamond doing the preliminary work finished off by a fire jet. Bases were also being rolled off an assembly line at this factory, the capacitoy of one base pressing machine alone being 2000 an hour.
