LATHE

Manual or electric, the lathe is a machining tool. Machining involves shaping a component by removing material using a cutting tool from the raw material. The operations that a lathe allows are circular, so it is mainly used to manufacture parts of circular shapes (cylindrical, conical, convex, concave, outer or inner diameters).

The raw material used to be worked with a lathe is (almost) exclusively in the form of a bar or tube. The bar of raw material is securely fixed at the centre of the lathe’s rotating axis (the headstock) using a clamp or chuck. The headstock is integral and perfectly aligned with the axis of a linear frame (the lathe bed) serving as support and guide for cutting tools (chisels).

There are lathes of all ages, sizes, and complexities. The smallest and simplest can be held in a bench vice and manually operated using a bow lathe. Such types of lathes are still frequently used today in artisanal manufacturing methods for producing components of small diameters (pinions, pivots, etc.). Most lathes nowadays are powered by electric motors driving their headstock through a belt or gear transmission.

By operating the bow lathe or the motor of the lathe, the headstock rotates on its own axis and thus drives the raw material. Unlike other machining tools (drilling machines, milling machines), with a lathe, it is the material that rotates and the tool that remains “fixed”.

Manually, the artisan uses a hand chisel that he holds firmly while resting on a support securely attached to the lathe bed. Depending on the lathe model or the dimensions of the component to be machined, the chisel will be securely screwed to a carriage, itself firmly attached to the lathe bed. Through racks and a precise system of slides, the carriage allows the chisel to be moved using cranks on two axes. By combining these two axes, the depth and diameter of each turning can be precisely adjusted. The lathe’s rotation speed is adjustable and set according to the material used, its dimensions, and the desired level of finish. The amount of material removed for each “pass” of the chisel is also significant in terms of precision and surface finish of the component after machining. Additional tools allow milling operations to be performed on a lathe. In such cases, the component remains fixed in its chuck on the headstock axis. The headstock is then disengaged so that it is no longer driven by the motor. The motor drives belts that actuate a mill attached to the lathe carriage. A dividing tool allows the headstock to be positioned at precise predefined angular intervals. It is thus entirely possible to fully turn (machine) a wheel on a lathe, and then cut its teeth.