Experiment Name: To study the construction of lathe machine and its different operations.
Introduction: Lathe machines create sophisticated parts for medical, military, electronics, automotive, and aerospace applications. Read on to find out the top 10 machining operations performed on a lathe. A lathe is capable of performing numerous machining operations to deliver parts with the desired features. Turning is a popular name for machining on a lathe. Nevertheless, turning is just one kind of lathe operation.
Objectives:
To explore the different of lathe machine.
To explore the different operations performed in lathe machine.
Figure: Lathe Machine
Bed: It is the main part of lathe machine. All the parts of machine are bolted on the machine bed that mainly comprise of headstock, tailstock, carriage guideways and other parts. It is made up of cast iron.
Head stoke: Headstock present on the left way of lathe. It is in alignment with tailstock. The headstock is made up of cast iron.
Tail stock: It is present on to the right side of the lathe machine. It provides the support to workpiece.
Carriage: It is situated between headstock and tailstock. It carries following parts as well like apron, saddle, compound rest, cross slide, and tool post.
Spindle: A hole in the back of the headstock assembly through which the rod stock is fed.
Chuck: A multi-jaw clamp to hold the rod stock in place while it is being machined. These can either be self-centering or independent of based on the number of jaws. Can be modified to mount oddly shaped workpieces that are not round/square/hexagonal.
Feed Rod: The primary power transition mechanism to move the carriage along the axis of the lathe. It will have two reversing gears attached to a piston to move the carriage forward or reverse.
Mandrel gear and pulley system: A workpiece which cannot be held between centers because its axis has been drilled or bored, and which is not suitable for holding in a chuck or against a faceplate, is usually machined on a mandrel. A mandrel is a tapered axle pressed into the bore of the workpiece to support it between centers.
Dead Center: A dead center (one that does not turn freely, i.e., dead) may be used to support the workpiece at either the fixed or rotating end of the machine. When used in the fixed position, a dead center produces friction between the workpiece and center, due to the rotation of the workpiece.
Saddle: It is H-shaped casting. The saddle connects the pair of bed guide ways as a bridge. It fits over the bed and slides along the bed between head stock and tail stock. The saddle can be moved by providing hand feed or automatic feed.
Tool Post: It is located on the top of the compound slide. It is used to hold the tools rigidly. Tools are selected according to the type of operation and mounted on the tool post and adjusted to a convenient working position. There are different types of tool post, which are as follows.
Lead screw: The lead screw of a lathe is used to advance the carriage of the lathe in time with the rotation of the spindle. It is used to make threads by having different gearing between the spindle and the drive for the lead screw.
Different Operations of Lathe Machine:
Turning: Turning is the most common lathe machining operation. During the turning process, a cutting tool removes material from the outer diameter of a rotating workpiece. The main objective of turning is to reduce the workpiece diameter to the desired dimension. There are two types of turning operations, rough and finish.
STEP TURNING
Step turning creates two surfaces with an abrupt change in diameters between them. The final feature resembles a step.
TAPER TURNING
Taper turning produces a ramp transition between the two surfaces with different diameters due to the angled motion between the workpiece and a cutting tool.
CHAMFER TURNING
Similar to the step turning, chamfer turning creates angled transition of an otherwise square edge between two surfaces with different turned diameters.
CONTOUR TURNING
In contour turning operation, the cutting tool axially follows the path with a predefined geometry. Multiple passes of a contouring tool are necessary to create desired contours in the workpiece. However, form tools can produce the same contour shape is a single pass.
2. FACING
During the machining, the length of the workpieces is slightly longer than the final part should be. Facing is an operation of machining the end of a workpiece that is perpendicular to the rotating axis. During the facing, the tool moves along the radius of the workpiece to produce the desired part length and a smooth face surface by removing a thin layer of material.
3. GROOVING
Grooving is a turning operation that creates a narrow cut, a "groove" in the workpiece. The size of the cut depends on the width of a cutting tool. Multiple tool passes are necessary to machine wider grooves. There are two types of grooving operations, external and face grooving. In external grooving, a tool moves radially into the side of the workpiece and removes the material along the cutting direction. In face grooving, the tool machines groove in the face of the workpiece.
4. PARTING
Parting is a machining operation that results in a part cut-off at the end of the machining cycle. The process uses a tool with a specific shape to enter the workpiece perpendicular to the rotating axis and make a progressive cut while the workpiece rotates. After the edge of the cutting tool reaches the center of the workpiece, the workpiece drops off. A part catcher is often used to catch the removed part.
5. THREADING
Threading is a turning operation in which a tool moves along the side of the workpiece, cutting threads in the outer surface. A thread is a uniform helical groove of specified length and pitch. Deeper threads need multiple passes of a tool.
6. KNURLING
Knurling operation produces serrated patterns on the surface of a part. Knurling increases the gripping friction and the visual outlook of the machined part. This machining process utilizes a unique tool that consists of a single or multiple cylindrical wheels (knurls) which can rotate inside the tool holders. The knurls contain teeth that are rolled against the surface of the workpiece to form serrated patterns. The most common knurling pastern is a diamond pattern.
7. DRILLING
Drilling operation removes the material from the inside of a workpiece. The result of drilling is a hole with a diameter equal to the size of the utilized drill bit. Drill bits are usually positioned either on a tailstock or a lathe tool holder.
8. REAMING
Reaming is a sizing operation that enlarges the hole in the workpiece. In reaming operations, reamer enters the workpiece axially through the end and expands an existing hole to the diameter of the tool. Reaming removes a minimal amount of material and is often performed after drilling to obtain both a more accurate diameter and a smoother internal finish.
9. BORING
In boring operation, a tool enters the workpiece axially and removes material along the internal surface to either create different shapes or to enlarge an existing hole.
10. TAPPING
Tapping is the process in which a tapping tool enters the workpiece axially and cuts the threads into an existing hole. The hole matches a corresponding bit size that can accommodate the desired tapping tool. Tapping is also the operation used to make a thread on nuts.
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