What are the major components of a lathe machine? Enlist various machine operations that can be carried out on the lathe machines.
Answer: Components of a lathe machine
The lathe machine essentially comprises the following major units:
1. Bed 2. Headstock 3. Tailstock 4. Carriage assembly 5. Tool post 6. Feed mechanism 7. Split nut mechanism 8. Compound rest.
1. Bed: The bed of the lathe forms the base of the machine. It is supported on two legs at a convenient height. It carries the headstock and the tailstock for supporting the work. It must also absorb vibrations likely to arise during the machining process.
2. Headstock: The headstock houses the spindle and the means for supporting and rotating the spindle. It is rigidly fixed on the bed. The spindle is made of steel.
3. Tailstock: Tailstock is the counterpart of the headstock fitted at the right-hand side of the bed.
4. Carriage assembly: The carriage assembly of the lathe consists of a number of components that support, move, and control the tool. The carriage assembly consists of a saddle, cross-slide, compound rest, top slide, tool post, and apron.
5. Tool post: It is the tool holding device located on the top of the compound rest. In addition to holding the tool, it enables the tool to be adjusted to a convenient working position.
6. Feed mechanism: It is used for transferring power from spindle to lead screw for obtaining different automatic feeds of the cutting tool.
7. Split‐nut mechanism: The split‐nut or half nut mechanism is used to engage or disengage the carriage with the lead screw for threading.
8. Compound rest: It is used for rotating the tool and tool post to perform the taper turning operations.
The various operation that can be performed on lathe machines are:
1. Facing: It is an operation for generating flat surfaces in lathes. The feed is given in a direction perpendicular to the axis of revolution.
2. Turning: It is a widely used operation in a lathe. The work held in the spindle is rotated while the tool motion is parallel to the axis of rotation, generating a cylindrical surface.
3. Knurling: It is the operation of plastically displacing metal into a particular pattern for the purpose of creating a hand grip or roughened surface on a workpiece.
4. Tapers and taper turning: A taper is defined as a uniform increase or decrease in the diameter of a piece of work measured along its length. In a lathe machine, taper turning means to produce a conical surface by a gradual reduction in diameter from a cylindrical job. The taper angle is given by relation.
tan a = ( D – d)/l
where D = The diameter of the large end of the cylindrical job,
d = The diameter of the small end of a cylindrical job, and
l = The length of the taper of cylindrical job, all expressed in inches.
A taper is generally turned in a lathe by feeding the tool at an angle to the axis of rotation of the workpiece. The angle formed by the path of the tool with the axis of the workpiece should correspond to the half taper angle.
5. Thread cutting: Thread of any pitch, shape, and size can be cut on a lathe using a single-point cutting tool. Thread cutting is the operation of producing a helical groove on a spindle shape.
6. Drilling: It is the operation of making cylindrical holes in the solid material. For producing holes in the workpiece on the lathe, the workpiece is held in a chuck or on a faceplate. The drill is held in the position of the tailstock and which is brought nearer to the workpiece by moving the tailstock along the guideways, thus the drill is fed against the rotating workpiece as shown in the figure.
7. Chamfering: Chamfering is used to avoid sharp edges, make assembly easier and improve aesthetics.
- Grooving :
- It produces a groove on the workpiece.
- The shape of the tool decides the shape of the groove.
- Carried out using a grooving tool, which is called a form tool.
- It also called turning.
- Cutting workpiece into two parts.
- Similar to grooving.
- A parting tool is used.
- Coolant is used for heat reduction.