The headstock is normally mounted rigidly to the bed and holds all the mechanisms, like combinations of pulleys or gears, controlling etc. Also it contain spindle. The spindle can be made to turn at different speeds.
The end of the headstock spindle is usually machined so that it can carry a faceplate,chuck,drive plate, internal or external collets – or even special attachments designed for particular jobs. In turn, these attachments hold the workpiece that is going to be machined.
As its name implies, backgear is a gear mounted at the back of the headstock (although in practice it is often located in other positions) that allows the chuck to rotate slowly with greatly-increased torque (turning power). Backgeared lathes are sometimes referred to a “BG” or “BGSC” – the latter meaning “backgeared and screwcutting”. At first, the ability to run a workpiece slowly might seem unnecessary, but a large-diameter casting, fastened to the faceplate and run at 200 rpm would have a linear speed at its outer edge beyond the turning capacity of a small lathe. By engaging backgear, and so reducing the speed but increasing the torque, even the largest faceplate-mounted jobs can be turned successfully.
important part on a lathe machine. Originally termed a “master thread”, or described as the “leading screw”, but now always referred to as the “leadscrew”, this is a long threaded rod normally found running along the front of the bed or, on some early examples running between the bed ways down the bed’s centre line. By using a train of gears to connect the lathe spindle to the leadscrew – and the leadscrew to the lathe carriage the latter, together with its cutting tool, could be forced to move a set distance for every revolution of the spindle.