The helicopter gearbox casings are magnesium castings around the size of a car and cost around £1/4 million pound each. Rather than replace the whole gearbox, when a bearing seating is worn it is bored out and a steel liner inserted into which the new bearing is fitted. With successive replacement cycles the bored out holes get bigger and bigger, so the liners come in a number of sizes.

The biggest gearbox component is a 9 ½ in diameter ring that is faced and machined on the internal and external diameters on the Matchmaker lathe. This is fitted with an 8 in chuck as standard, but on this machine the jaws have been extended to take larger diameters.

Warren Bell says that there is plenty of clearance to swing even larger parts, and adds that it is a powerful machine. It needs to be. The liners are made from aircraft steel, with the blanks cut by water jet. The parts are rough machined to within 3mm of the final size all over the surface and then heat treated before final machining in the hardened state.

Components for helicopter gearboxes are turned on the Matchmaker Super Slant 200S lathe

www.murray-productions.co.uk