MACHINE TOOLS - LATHE

MACHINE TOOLS:
- Machining equipment that cuts, shears, punches, presses, drills, grinds.

- The removed part of materials from the work piece is called as chips
- Machine tools are generally the power driven metal cutting or metal farming machines used to
alter/change the workpiece to the required shape and size by:

1. Cutting away the unwanted sections
2. Pressing, drawing, punching or shearing
3. Controlled electrical machinery process

LATH MACHINE

PARTS OF LATH MACHINE

1. BED :

- The bed is a heavy, rugged casting in which are mounted the working parts of the lathe.

- It carries the headstock and tail stock for supporting the workpiece

- provides a base for the movement of carriage assembly which carries the tool.

- Bed is a massive single casted component 

2. HEAD STOCK

- The headstock is permanently clamped on the left hand side of the bed

- it serves as housing for the driving pulleys, back gears, headstock spindle, live centre and the feed

reverse gear.

- The headstock spindle :

- is a hollow cylindrical shaft that provides a drive from the motor to work holding devices.

- Spindle is the primary working unit

- Chuck is fixed to the spindle and work piece is fixed to the chuck

- Live centre is the tapered section with included angle 60* , the work piece is attached to the live

centre, work piece rotate based on live centre

3. TAIL STOCK

- The tailstock is a movable casting located opposite the headstock on the ways of the bed.

- The tailstock can slide along the bed to accommodate different lengths of workpiece between

the centers.

- A tailstock clamp is provided to lock the tailstock at any desired position.

- The tailstock spindle has an internal taper to hold the dead centre and the tapered shank tools

such as reamers and drills.

- Dead centre is provided to hold long work piece ( L/D > 4 ) to support the both ends

- The lower portion - comprises of the movable part on which the tail stock slides

- The upper portion - can be made inclined or straight position

- Quill : similar mechanism and function as that of spindle in headstock ( has only sliding motion )

dead centre is fixed at the centre of quill

4. CARRIAGE

- Carriage is a moving part which moves on the bed and provide movement to the tool

- LEAD SCREW : leads the movement of the carriage

- CARRIAGE PARTS :

- SADDLE :

- H shaped casting fit over the bed and slides along the way

- Cross slide and tool post are carried by the saddle

- CROSS SLIDE :

- Mounted on top of saddle

- Provides manual or automatic cross movement for cutting tool

- Provides cross feed to the tool

- COMPOUND REST :

- fitted on top of crossslide

- Used to support cutting tool and has a circular base

- Swiveled to any angle for taper-turning

- Has graduated collar that ensure accurate cutting-tool settings (.001 in.)

- TOOL POST :

- Mounted on the compound rest

- Rigidly clamps the cutting tool or tool holder at the proper height relative to the work

centre line.

- APRON :

- Apron is fastened to the saddle and it houses the gears, clutches and levers required to

move the carriage or cross slide. 

- Locking-off lever inside apron prevents engaging split-nut lever and automatic feed lever

at same time

- Apron hand wheel is turned manually to move carriage along lathe bed

DRIVES 

1. MAIN DRIVE: Drives the spindle 

2. FEED DRIVE: Drives the feed tools 

SURFACES 

1. CYLINDRICAL: Tool feed parallel to the axis of spindle while work rotates 

2. FLAT SURFACE: Tool feed perpendicular to the spindle axis while work rotates

LATH OPERATIONS 

1. TURNING : Removal of exess amount of material from outer diameter to inner diameter to form conical or cylendrical shape 

- ROUGH TURNING : removal of metal in minimum time with high feed speed and high depth – hence less accuracy 

- FINISH TURNING : low feed speed and depth of cutting – hence high accuracy and smooth surface 

- PLAIN TURNING: Plain turning is the operation of removing excess amount of material from the surface of a cylindrical job. 

- STEP TURNING: Step turning produces various steps of different diameters

- TAPER TURNING : Turning with a uniform increase or decrease in diameter of work piece along the length 

2. FACING: 

- The facing is a machining operation by which the end surface of the workpiece is made flat by removing metal from it. 

- Also used to cut the work piece in desired length 

3. PARTING: The parting or cutting off is the operation of cutting away a desired length of the workpiece, i.e., dividing the workpiece in two or more parts. 

4. DRILLING:  Drilling is the operation of producing a cylindrical hole in the workpiece.

5. REAMING: 

- The holes that are produced by drilling are rarely straight and cylindrical in form. 

- The reaming operation finishes and sizes the hole already drilled into the workpiece. 

6. BORING: The boring operation is the process of enlarging a hole already produced by drilling

7. KNURLING: 

- The knurling is a process of embossing (impressing) a diamond-shaped or straight-line pattern into the surface of workpiece. 

- Knurling is essentially a roughening of the surface and is done to provide a better gripping surface.

8. GROOVING: Grooving is the act of making grooves of reduced diameter in the workpiece. 

9. THREADING: Threading is the act of cutting of the required form of threads on the internal or external cylindrical surfaces. 

10. FORMING: The forming is an operation that produces a convex, concave or any irregular profile on the workpiece.

11. CHAMFERING: Chamfering removes the burrs and sharp edges, and thus makes the handling safe. Chamfering can be done by a form tool having angle equal to chamfer which is generally kept at 45°.   

12. FILING AND POLISHING: The filing is the finishing operation that removes burrs, sharp corners and feed marks from the workpiece. After filing, the surface quality is the workpiece is improved by the polishing operation with the help of emery cloth of fine grades. 

13. TAPER TURNING: The taper turning is an operation of producing a conical surface by gradual reduction in the diameter of a cylindrical workpiece. 

14. MILLING : Work piece is fixed in the head stock and is feed on to the rolling cutter having multiple cutting edges 

15. GRINDING : Metal is removed in the form of minute chips by feeding on to a rotating abrasive wheel known as grinding wheel 

FIGURES RELATED TO LATHE MACHINE