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Atlas Zamak Components
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Atlas 6-inch with Screwcutting Gearbox

Even in pre-WW2 years Atlas had made novel use of new materials and all models had their changewheels, most other gears, handwheels, pulleys, clasp nuts and other small items made from "Zamak". Two of the three 10-inch copies made in  England under the "Acorntools",  "Sphere" and "Halifax" labels went further and had several parts including the headstock 4-step pulley, changewheel guards and shell of the bed-mounted reversing gearbox made from an early form of black plastic. Zamak (a registered trade mark) is an alloy of Zinc, Aluminum, MAgnesium, and Kupfer (kupfer is German for copper) pressure injected into hardened-steel dies. It was developed by the New Jersey Zinc Company (based near the Franklin and Sterling Hill mines of northern New Jersey where the zinc ore was extracted) and employed from the very beginning of Atlas lathe production in 1932 on the 9-inch model. The use of ZamakK would have required a number of expensive steel dies - and Atlas must have reckoned on selling substantial numbers of machines to recoup their investment. However,  one very important advantage of Zamak was a surface finish so smooth that the need for machining was often eliminated, leading to a substantial saving in both production time and cost. The mix used to produce Zamak has always varied to suit a particular application - for example Zamak 5 consists of 4% Aluminium, 1% Copper, 0.05% Magnesium with the rest Zinc - and it is known that Atlas choose to use one of the more durable varieties - even though, due to the higher casting temperatures needed, die life was shortened. The Zamak process represents one of the shortest paths available between metal raw material and a finished product; it is still widely used today and should not to be confused with "pot metal", a cheap alloy of mainly lead and zinc, often used in the production of toys, that can eventually crumble to dust. Unfortunately, one of the drawbacks of even high-quality Zamak is that any contamination at the casting stage will shorten part life and lead, eventually, to failure. Unless post-production testing is carried out on a regular basis this problem will not be picked up until, many years later, examination of identical components (used in the same environment) will show some to be as-new - but others weakened to a state of hopeless disintegration..