functions of lathe

MAJOR FUNCTIONS:

• BED: The bed is the foundation of a lathe and supports all its parts. The top of the bed is formed by precision machined guideways. There will be two sets of guideways, viz... Outerways and Innerways. The headstock and the tailstock are mounted on the innerways which keep them perfectly aligned with each other. The outerways guide the longitudinal movement of the carriage assembly and align it with the centre line of the lathe.

• MAIN DRIVE: An electric motor mounted in the left leg of the lathe in conjunction with the transmission system like belt or gear drive from the motor to the spindle that form the main drive of the lathe.

• CONE PULLEY AND BACK GEAR: The cone pulley which drives the main spindle through belting is driven by the motor. Various spindle speed can be obtained by shifting the belt on the different steps of the cone pulley. Spindle speed can be further varied using a back gear arrangement.

• HEADSTOCK: The housing comprising of the feed gear box and the cone pulley is called headstock of the lathe. The main spindle projects out from the headstock. The headstock will be rigidly mounted on the lathe bed at its left end.

• TAILSTOCK: It is the movable part of the lathe that carries the dead centre in it. The main function of tailstock is to support the free end of the long workpiece. It also used to clamp the tools like twist drills and reamers for making holes, and taps and dies for cutting threads. Tailstock is mounted loosely on the lathe bedways and can be moved and locked in any desired position. 

• LEAD SCREW: It is a screw rod which runs longitudinally infront of the lathe bed. The rotation of the lead screw moves the carriage to and fro longitudinally during thread cutting operations.

• FEED ROD: The feed rod is a stationary rod mounted infront of the lathe bed and facilitates longitudinally movement of the carriage during turning, boring and facing operations.

• FEED GEAR BOX: The feed gear box is mounted on the left side of the lathe bed and below the headstock. It houses the necessary gears and other mechanisms that transmit various feed gear ratios from the headstock spindle to either the lead screw or the feed rod.

• CARRIAGE ASSEMBLY: The carriage assembly serves to support the tool and rides over the bedways longitudinally between the headstock and tailstock. It is composed of five main parts.

a) Saddle: is a H shaped casting slides over the outer set of the guideways and serves as the base for the cross slide.

b) Cross Slide: is mounted on the saddle and enables the movement of the cutting tool laterally across the lathe bed by means of cross-feed hand wheel. It also serves as the support for a compound rest.

c) Compound Rest: is mounted on the top of the cross slide and supports the tool post. It can be swiveled to any angle in the horizontal plane to facilitate the taper turning and threading operations. It is moved manually by the compound rest feed handle independent of the lathe cross feed.

d) Apron: is mounted at the front of the saddle beneath it and houses the carriage and the cross slide mechanisms. The apron hand wheels moves the carriage assembly manually by means of the rack and the pinion gears.

e) Tool Post: is mounted in the T slot of the compound rest. The tool post clamps the tool holder in the proper positions for machining operations.