Centre lathe: operation

The lathe is the oldest machine tool, the first to be invented and, moreover, one of the most widely used today. On the lathe many machining operations can be carried out; it is a very easy machine to use and the tools it needs can be prepared in a short time. Among the different types of lathe that exist today, the centre lathe and how it works may interest you if you are looking to transform solid parts.

What is a centre lathe?

The lathe is one of the most widely used tools in machining workshops. Whatever the type, most workshops need them for the production of parts, mostly cylindrical ones, but also for drilling and grooving, among other tasks. The centre lathe makes it possible to transform a piece of metal (raw material) into another with a specific design.

Lathes are characterised by the fact that the workpiece is mounted on a jaw chuck, using one of the recommended clamping systems. The clamped workpiece rotates until it meets the edge of the cutting tool. These machines can use drill bits and lathe tools to machine parts by metal cutting.

Centre lathe: operation and parts

The centre lathe consists of a headstock inside which the spindle turns; its structure also includes a pair of longitudinal guideways, parallel to each other and to the spindle itself. On the spindle nose there is a universal chuck or three-jaw chuck that is used to centre the workpiece and give it the rotary movement it must make until it meets the end of the cutting tool. Once the workpiece has been placed on this chuck and clamped to it by one of the many clamping systems, the lathe can run.

On the guideways of the centre lathe, the tailstock can slide, its axis coinciding with that of the fixed headstock. In it there is a bar with one end that can be fitted to the lathe's tailstock centre; however, this is intended for machining between centres. Between the fixed headstock and the tailstock, and along a set of guideways, the tool-holder carriage slides. This movement can be manual or driven by the machine's handwheel. On the centre lathe, when the carriage is operated manually, the handwheel turns a pinion that engages the fixed rack located on the bed.

When the machine is operated according to the feed movement, this transmits the rotation to be followed by the feed rod, the lead screw or any other tool used for the various machining operations on this machine. In turn, on the lathe carriage and transversely to the guideways, the tool turret can move.

Now that you know what the centre lathe is and how it works, you should know the parts that make it up:

• Bed: this is the structure of the machine, on which all its elements rest. The tailstock, steady rests and carriage slide on the bed; this is made possible by straight guideways.
• Fixed headstock or chuck: this is where the transmissions and gears that allow the machine to run at different speeds are concentrated; these speeds are transmitted to the jaw chuck on which the workpiece is mounted.
• Tailstock or movable headstock: used to hold the workpiece correctly when turning between centres. It houses the tailstock centre.
• Carriage or turret: where the tools used to machine the parts are fixed. The carriage moves along the bed and can be manual or motorised. It can move longitudinally, but also on the other two axes.
• Steady rest: used for machining large parts.
• Cutting tools: as the lathe is a versatile machine capable of many machining procedures, it requires different tools. Most commonly it uses lathe tools, which are specific to lathes; when the machining is drilling, the lathe must use drill bits.

Operation

For the lathe to work as it should, certain aspects and recommendations must be taken into account. We begin by telling you that the operator must carry out a series of checks before machining. The operator must check that the machine is connected through a circuit with a residual-current device. This must be earthed and have a sensitivity switch.

It must also be checked that the chuck and its lock are correctly fitted and, of course, that the workpiece is firmly clamped in the chuck. It must be checked that the machining area of the machine is clean, that is, that there is no accumulated swarf that could prevent the centre lathe from working properly.