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THE LATHE

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1. The Lathe (Schaublin 70)

2. General description

Manual or electric, the lathe is a machining tool. Machining consists of shaping a component by removing material using a cutting tool on the raw material. The machining operations that the lathe allows are circular in shape. It is therefore mainly intended for manufacturing parts of circular shape (cylindrical, conical, convex, concave, external or internal diameters).

3. Raw material

The raw material intended to be worked using a lathe is (almost) exclusively presented in the form of a bar or a tube. The bar of raw material is firmly fixed at the center of the rotating axis of the lathe (the headstock) using a collet or a chuck. The headstock is fixed and perfectly aligned with the axis of a linear frame (the lathe bed), which serves as a support and guide for the cutting tools (gravers).

4. Diversity of ergonomics and applications

There are lathes from all eras, of all sizes and all levels of complexity. The smallest and simplest ones can be held in the vice of a bench and manually activated using a bow. This type of lathe is still frequently used today according to artisanal manufacturing methods for the production of small-diameter components (pinions, pivots, etc.). Most lathes are nowadays powered by electric motors, which drive their headstock via a belt or gear transmission.

5. Operating principle

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

Manually, the craftsman uses a hand graver which he holds firmly while resting on a support solidly fixed to the bench of the lathe. Depending on the lathe model or the dimensions of the component to be machined, the graver will be firmly screwed to a carriage, itself solidly fixed to the bench of the lathe. Thanks to racks and a precise slide system, the carriage allows the graver to be moved using cranks along two axes. By combining these two axes, one can precisely adjust the depth and diameter of each turning operation. The rotation speed of the lathe is adjustable and adapted to the material used, its dimensions, and the desired level of finish. The amount of material removed at each “pass” of the graver is also decisive for the precision and surface condition of the component after machining. Additional tools allow milling operations to be carried out on a lathe. In such cases, the component remains fixed in its collet on the axis of the headstock. The headstock is then disengaged so that it is no longer driven by the motor. The motor then drives belts which operate a milling cutter fixed to the carriage of the lathe. 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, then cut its teeth on it. A tailstock fixed to the bench of the lathe allows workpieces to be worked between centers, to perform drilling and various other operations.

6. Different types of lathes

• The parallel lathe
• The automatic lathe
• The pivoting lathe
• The horologist’s (watchmaker’s) lathe
• The fixed graver
• The turret lathe
• The pantograph lathe
• The rose engine (guilloché lathe)