4) Lathe construction features and functions

9.4 LATHE CONSTRUCTION FEATURES AND FUNCTIONS

Lathe Machine consists –bed –headstock –tailstock –carriage assembly –quick-change gearbox

Bed

· Made of gray or ductile cast iron or fabricated from steel by welding

· Divided in to 2 ways

1. Outer ways

2. Inner ways

· Headstock and tailstock located on the inner ways

· Guides the longitudinal movement of the carriage assembly and alignsot wotje the centerline of the of lathe

· Precision machined, ground and hand scraped to provide the exactness needed for the other mating parts

· Clear the bed before using to avoid damaging

· Oil the ways for further protection to ensure that carriage assembly can move smoothly

Headstock

· Mounted at the left hand side of lathe machine.

· To turn the work piece and is where work-holding attachments mount.

· The spindle is driven by an electric motor through a system of belt drives and/or gear trains.

· The main spindle is mounted on bearings in the headstock and is hardened and specially ground to fit different lathe holding devices

· Spindle speed is controlled by varying the geometry of the drive train. (which is achieved by turning the gear level into a desired position)

· Various work holding attachments such as three jaw chucks, collets, and centers can be held in the spindle.

· Feed Reverse also located on the headstock-reverse the rotation of feed rod and lead screw and change the direction of movement of carriage

Tailstock

· Support the end of longer work piece

· The tailstock holds such cutting tools for internal machining operations.

· The spindle is graduated to control the depth of drilling operations.

· Can be moved along the ways to accommodate various lengths of work.

· Is fastened into position by tailstock clamp

· Tailstock spindle can be adjusted longitudinally by rotating hand wheel and locked by tailstock spindle lock

·

Adjusting screws hold the tailstock that made in two part.

· It allow the top part to move toward or backward from the operator

· For turning tapered parts or aligning the tailstock spindle true with headstock spindle

· Must be realigned exactly on center when turning a cylindrical part

Carriage Assembly

· Move along ways longitudinally

· Saddleà an H-shaped casting fitted to the outer set of ways

· Cross Slideà mounted on top of the saddle and moves the cutting tool laterally across the bed by cross-feed hand wheel that has a micrometer collar that allows the cuttings tool to remove metal in thousandths of an inch.

· Compound Restà mounted on the cross slide and support the tool post. can be swiveled to any angle for taper turning or threading operations. Moved by compound rest feed handle and screw tat has a micrometer collar that same with cross-feed handwheel.

· Apronà mounted beneath the front of saddle and houses the carriage and cross-slide control mechanisms. The apron handwheel is used to moved the carriage assembly by rack and pinion gears. Contained automatic fed lever that is used for engaging power feeds of either the carriage assembly or cross slide.

· Toolpostàmounted in the T-slot of the compound rest. Clamps the toolholders in the proper position for machining operations.

Carriage + saddle

Quick-change Gearbox

· Mounted on the left side of bed and below the headstock

· Houses necessary gears and other mechanisms that transmit various feed rates from the headstock spindle to either the lead screw or feed rod.

· Lead screw advances the carriage during threading operations; feed rod moves the carriage during turning, boring, and facing operations

· They have shear pins or slips clutch to avoid damage to gearbox.