The lifeblood of a drill-making factory
The grinding of HSS to make drill bits produces metal swarf, grinding-wheel particles, and heat. The drill blank is flooded with Houghton flute-grinding oil to reduce friction; reduce wear on the grinding wheels; carry away both heat and, suspended in the oil, the metal and alumina particles formed by the grinding process.
“You can’t grind without oil,” is one of Rick Smith’s sayings. This means that the Kaiapoi factory is plumbed throughout for oil, just like the circulatory system of some gigantic beast. One set of pipes, like an animal’s arteries, carries cool, filtered oil to the machines. These dangle from the factory’s ceiling like outsized plastic umbilical cords. Another set of pipes, vein like, carries hot, debris-laden oil away to the pumps — the heart of the system. There are two separate networks, with each having a set of filters, heat exchangers, and pumps. One system circulates 30,000 litres, the other 20,000 litres. The heat exchangers transfer the heat in the hot oil to the air, reducing the oil’s temperature from about 100°C to 40°C. Cooler oil is more viscous so it evaporates less, collects heat from the workpiece better, and smokes less.
The particles filtered out of the oil are valuable because they are rich sources of scarce metals such as tungsten, chromium, and cobalt. The filtered metal and grinding-wheel particles are packed into drums and exported to Asia to be reprocessed. The grinding oil is sufficiently expensive to make it worthwhile to remove as much as possible from the filtered grindings by pressing. The high-tech and powerful presses used to do this are made in the Kaiapoi factory. So far they have made six.
Magnetite-coated HSS (top) and reduced-shank HSS (bottom) twist drills