The headstock - The back gear LATHE

The headstock The headstock is secured permanently on the inner ways as the left hand end of the lathe bed, and it provides mechanical means of rotating the work at multiple speeds. It comprises essentially a hollow spindle and mechanism for driving and alternating the spindle speed. All parts are housed within the head stock casting. The spindle of headstock is made of carbon or nickel-chrome steel. The back gear The back gear is an additional feature of a belt driven lathe and is used to obtain wider range of spindle speeds, for the number of speeds obtained from “direct speeds” is limited to number of steps only. When the back gear is engaged, the spindle is speed is reduced considerably. So it is also used when it is necessary to have a slow speed of the spindle that cannot other wise be obtained by direct speed. A slow speed is necessary in the following cases. 1.In turning jobs of large diameter within the available cutting speed of the material 2.In turning jobs tough or hard material when the material is hard it becomes necessary to apply greater cutting force by the tool to shear out the metal. This increase in cutting force will require greater turning torque necessitating slower spindle speed. 3.In operations like thread cutting, reaming, e.t.c. 4.In taking deep cut as rough turning.
fr. NTTF ( NETTUR TECHNICAL TRAINING FOUNDATION)