1 Buying Your First Lathe

WHAT SIZE OF LATHE DO I REQUIRE?

The first thing to consider when buying a lathe is the size of the work that you want to do. What is the largest diameter you will want to turn on it and what is the longest length you will need to turn? A 3½ × 18in (90 × 457mm) lathe will allow a maximum diameter of 7in (178mm) to be turned over the lathe bed; the latter figure is known as the swing. In practice, though, this is atheoretical maximum as it is still necessary to hold and clamp the article being turned. The swing over the cross slide is usually much smaller, typically 2in (50mm).

Many lathes, however, are manufactured with a gap bed at the headstock end to enable short items of a large diameter, such as locomotive or traction engine wheels, to be turned.

Lathes are also sometimes available as standard and long bed lathes. The long bed lathe, as the name suggests, allows longer material to be turned within the capacity of the lathe. When turning longer material, the diameter will be limited by the swing over the cross slide. This will be a lot smaller than the swing over the bed.

If building a model such as a traction engine or a locomotive, the deciding factor for the size of lathe is likely to be thediameter of the largest pair of wheels that need to be turned. Before deciding on the size of lathe required you should determine the size of the largest diameter and the longest length of material that needs to be turned. Another factor in determining what lathe to buy is the availability of spares and accessories: is the company still trading, will it still be trading in the future, and are there large amounts of second-hand parts and accessories available from tool dealers or on eBay?

LATHE ELECTRICS

Single phase electric is where the lathe plugs into the mains supply in your house. The motor will have the usual live, neutral and earth leads. Lathes supplied for factory use usually have three phase motors and require three live wires, each of a different phase. Think of a phase as an incoming wave on the seashore; three successive waves make up the three phases needed. Each phase is the same as the preceding one but they are out of sync and all peak at adifferent time.

Converters and inverters

You can run some 3 phase motors from a single phase supply via a converter or an inverter. The motor information plate will usually say 240 volts/440 volts if it is capable of running on an inverter. Inside the motor there will be changeover tags to change the motor from 440V down to 240V. Follow the converter/inverter manufacturer’s instructions for further information. It is not usually very complicated to run a 240V 3 phase motor from an inverter and this will give a quieter and smoother running motor than a single phase supply can provide. Thisusually requires some simple programming, explained in the inverter’s instructions, and it usually takes five minutes to get the motor working properly.