Features and working of a lathe

A lathe is basically composed of a long horizontal base, one end of which is attached with an accurate turning apparatus, called the headstock. The headstock contains the spindle, which is an axle parallel to the base. The opposite end of the base consists of the tailstock. The material to be polished, cut, or shaped is held rigidly between the headstock chuck and the tailstock. Both the headstock and the tailstock can be slided over the base with a handwheel and then locked into place depending on the length of the workpiece or the task to be performed. When the workpiece is clamped between the headstock and the tailstock, it is considered to be ‘between centers’, while when it is fixed only to the spindle, it is regarded as being ‘face work’. While the ‘between centers’ mode of fixing the workpiece is more stable, the ‘face work’ method allows tasks to be carried out on the cross section of the workpiece.

The cutting or shaping bit is normally attached to a tool post that is attached to a cross slide that essentially slides over a rail on the base. The cutting bit is positoned to touch the material being shaped. When the lathe is started, the spindle begins rotating rapidly and this initiates the cutting action when the cutting bit is brought into contact with the material. For polishing and smoothening tasks, the cutting bit is replaced with a sandpaper roller. During usage, the headstock is continuously oiled to ensure smoothness and prevent disruptions due to friction. The movement of the tool post is either managed through computer controlled motors or manually with the handwheels. While the cutting or scraping action is being carried out a nozzle over the tool post sprays a cooling and lubricating fluid over the cutting area to prevent overheating and also to minimize the occurrence of kickbacks due to any kinks in the material or the cutting bit being plunged in too deep.

The rotational motion of the spindle is powered by an approximately 2 amp motor, generating a maximum output speed of around 3000 revolutions per minute (rpm). The power is transmitted only to the spindle and not to the tailstock. A variable speed feature allows the user to choose between around 8 different speeds, depending on the intended task. Apron mounted inch metric dials are provided for efficient spindle actuation control. The tool body is generally made of cast iron to increase sturdiness and reduce vibrations during operation. The spindle power transmission is mostly achieved with a V-belt.  
 
Most lathes have a 14 swing and a 42 turning capacity, with a complete 4 ram travel limit on the tailstock. For added versatility, the headstock can be swiveled 360 degrees, with positive stops provided at 45 and 90 degrees. The spindle, too, offers positive indexing in regular increments of 10 degrees, which is useful for veining and fluting. Often, an approximately 12 inch cast iron tool rest and a 6 inch face plate with a ball bearing live center are incorporated into the lathe.

What to look for in a lathe

Depending on space constraints and the intended location of the tool, the operator can chose between a bench-top and a floor model having legs. A precision ground spindle with tapered roller bearings increases the accuracy of the tool. An enclosed gearbox enhances the smooth and noiseless operation of the lathe. Hardened and ground gears increase rigidity and durability. A digital readout enables the user to instantly see the speed of the spindle, so that quick changes can be made as and when needed.

Some lathes have a tool caddy which can be hung just below the headstock to provide a convenient place to store the regularly used accessories. Some reputed manufacturers of lathes include Delta, Jet, Kwik-Way, Performance, Powermatic, and TD Industrial.

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