pro lab manual mgr

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STUDY OF LATHE

Aim

To study about the lathe

Introduction

Lathe is called the father of machine tools. The main function of lathe is toremove metals from work piece to give a required shape and size. In the lathe the workpiece is held in a chuck. The tool is moved at an angle 90 to the axis. Variousoperations such as straight turning, taper turning, and chamfering, facing, knurling,grooving, thread cutting, taper turning are carried out. When the operations above setare done automatically, then the lathe is called automatic lathe.

Working principle of lathe

In a lathe, the work piece is held in chuck and rotates about its axis by means ofpower. A single point cutting tool is mounted in tool post. When the chuck rotated thework piece also rotated. The tool moves parallel to the axis of rotation of work piece toproduce a cylindrical surface, where as the tool moves perpendicular to the work piece

to produce a flat surface. The tool moves at an angle to the axis of work piece toproduce a turn surface. The material is removed in the form of chip from the work pieceby giving proper feed and depth of cut. So, the required size and shape of the work isobtained.

Main parts of lathe

The lathe consists of various parts. Their parts and function are discussed below.

Bed

Bed is the base of the lathe. The headstock is mounted on the left end; thecarriage is in the middle and the tailstock at the right end of bed. The bed is made up of

cast iron, alloyed with nickel, chromium. The bed is made up of cast iron to observeshock and vibration created during machining. The guide ways of the bed may be flatterinverted V shape.

Headstock

It is mounted on the left end of the bed. It carries a hollow spindle. The live centercan be attached in the spindle. The spindle nose is threaded. In chuck faceplates canbe attached to the spindle. The headstock may be back threaded type. The headstockhas two types of driving mechanism

Back geared mechanism

Belt driven mechanism

Tailstock

It is located on the bed at the right end. It is used for supports right end of workand also for holding drills, reamer tools for drilling, reaming and such other operations.The tailstock can be moved along the bed and clamped at any position, to support thedifferent length work.


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Carriage

Carriage is used for giving various feed to the tool by hand or by power.The carriage is attached with the saddle.

Saddle

It is a H shaped casting fitted on the bed and moves along the guideways. It carries the cross slide, compound rest and a tool post.

i) Cross slideIt is attached to the upper side of saddle and carries compound slide and tool

post. The cross slide can be moved cross wise by hand or power. The micrometer dialis mounted on the cross slide hand wheel, with an accuracy of 0.05mm.

ii) Compound Rest

It is attached over the cross slide. It is used during the taper turning openingoperations to set the tool for angular cuts. Here the micrometer dial is mounted to showthe depth of cut.

iii) Tool post

The tool is clamped over the tool post. It is fixed over the compound rest. Thereare four types of tool post

a. Single screw tool post

b. Open side tool post

c. Four bolt tool post

d. Four way tool post

Apron

Apron is attached to the saddle and hangs in front of the bed. It has gears,

levers, clutches for moving the carriage automatically. A split nut is attached forengaging and disengaging the carriage from the lead screw. It is used in thread cuttingwork.

Lead Screw

It is a longer screw with standard ACME square threads and used for transmittingpower for automatic feed for thread cutting operation.

Feed rod

The feed rod is the long shaft used for the movement of carriage alongthe axis of bed. It is used for operations like facing, turning and boring.

RESULTThus the lathe was studied.


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A MILLING MACHINE

A milling machine is a machine tool used to machine solid materials. Milling

machines are often classed in two basic forms, horizontal and vertical, which refers to

the orientation of the main spindle. Both types range in size from small, bench-mounted

devices to room-sized machines. Unlike a drill press, which holds the work piece

stationary as the drill moves axially to penetrate the material, milling machines also

move the work piece radially against the rotating milling cutter, which cuts on its sides

as well as its tip. Work piece and cutter movement are precisely controlled usually by

means of precision ground slides and lead screws or analogous technology. Milling

machines may be manually operated, mechanically automated, or digitally automated

via computer numerical control(CNC).

Milling machines can perform a vast number of operations, from simple (e.g., slot

and keyway cutting, planing, drilling) to complex (e.g., contouring, die sinking). Cutting

fluidis often pumped to the cutting site to cool and lubricate the cut and to wash away

the resulting swarf.

Types and nomenclature

Mill orientation is the primary classification for milling machines. The two basic

configurations are vertical and horizontal. However, there are alternate classifications

according to method of control, size, purpose and power source.

Mill orientation

Vertical mill

Vertical milling machine. 1: milling cutter 2: spindle 3: top slide or overarm 4: column 5:

table 6: Y-axis slide 7: knee 8: base
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In the vertical mill the spindle axis is vertically oriented. Milling cutters are held in the

spindle and rotate on its axis. The spindle can generally be extended (or the table can

be raised/lowered, giving the same effect), allowing plunge cuts and drilling. There are

two subcategories of vertical mills: the bed mill and the turret mill.

A turret mill has a stationary spindle and the table is moved both perpendicular

and parallel to the spindle axis to accomplish cutting. The most common example

of this type is the Bridgeport, described below. Turret mills often have a quill

which allows the milling cutter to be raised and lowered in a manner similar to a

drill press. This type of machine provides two methods of cutting in the vertical

(Z) direction: by raising or lowering the quill, and by moving the knee.

In the bed mill, however, the table moves only perpendicular to the spindle's axis,

while the spindle itself moves parallel to its own axis.

Turret mills are generally considered by some to be more versatile of the two

designs. However, turret mills are only practical as long as the machine remains

relatively small. As machine size increases, moving the knee up and down requires

considerable effort and it also becomes difficult to reach the quill feed handle (if

equipped). Therefore, larger milling machines are usually of the bed type.

Also of note is a lighter machine, called a mill-drill. It is quite popular with hobbyists,

due to its small size and lower price. A mill-drill is similar to a small drill press butequipped with an X-Y table. These are frequently of lower quality than other types of

machines.

Horizontal mill

Horizontal milling machine. 1: base 2: column 3: knee 4 & 5: table (x-axis slide is

integral) 6: overarm 7: arbor (attached to spindle)
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A horizontal mill has the same sort ofxytable, but the cutters are mounted on a

horizontal arbor (see Arbor milling) across the table. Many horizontal mills also feature a

built-in rotary table that allows milling at various angles; this feature is called a universal

table. While endmills and the other types of tools available to a vertical mill may be used

in a horizontal mill, their real advantage lies in arbor-mounted cutters, called side and

face mills, which have a cross section rather like a circular saw, but are generally widerand smaller in diameter. Because the cutters have good support from the arbor and

have a larger cross-sectional area than an end mill, quite heavy cuts can be taken

enabling rapid material removal rates. These are used to mill grooves and slots. Plain

mills are used to shape flat surfaces. Several cutters may be ganged together on the

arbor to mill a complex shape of slots and planes. Special cutters can also cut grooves,

bevels, radii, or indeed any section desired. These specialty cutters tend to be

expensive. Simplex mills have one spindle, and duplex mills have two. It is also easier

to cut gears on a horizontal mill. Some horizontal milling machines are equipped with a

power-take-off provision on the table. This allows the table feed to be synchronized to a

rotary fixture, enabling the milling of spiral features such as hypoid gears.
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A GRINDING MACHINE

A grinding machine, often shortened to grinder, is a machine tool used for

grinding, which is a type ofmachining using an abrasive wheel as the cutting tool. Each

grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear

deformation.

Grinding is used to finish workpieces which must show high surface quality (e.g.,

low surface roughness) and high accuracy of shape and dimension. As the accuracy in

dimensions in grinding is on the order of 0.000025mm, in most applications it tends to

be a finishing operation and removes comparatively little metal, about 0.25 to 0.50mm

depth. However, there are some roughing applications in which grinding removals high

volumes of metal quite rapidly. Thus grinding is a diverse field.

Introduction

The grinding machine consists of a power driven grinding wheel spinning at the

required speed (which is determined by the wheels diameter and manufacturers rating,

usually by a formula) and a bed with a fixture to guide and hold the work-piece. The

grinding head can be controlled to travel across a fixed work piece or the workpiece can

be moved whilst the grind head stays in a fixed position. Very fine control of the grinding

head or tables position is possible using a vernier calibrated hand wheel, or using the

features ofnumerical controls.

Grinding machines remove material from the workpiece by abrasion, which can

generate substantial amounts of heat; they therefore incorporate a coolant to cool the

workpiece so that it does not overheat and go outside its tolerance. The coolant also

benefits the machinist as the heat generated may cause burns in some cases. In very

high-precision grinding machines (most cylindrical and surface grinders) the final

grinding stages are usually set up so that they remove about 200 nm (less than

1/100000 in) per pass - this generates so little heat that even with no coolant, the

temperature rise is negligible.

Kinds of Grinding

Surfaces of almost all conceivable shapes and materials of all kinds are suitable for

grinding. This operation can classify broadly into two groups:
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1. Rough or non-precision grinding.

2. Precision grinding.

Principal grinding operations

Principal operations which may be done on grinding machines includes the

grinding of external and internal cylindrical grinding, tapered and formed surfaces, gear

teeth, threads and others using appropriate wheels and fixtures of each job. External

and internal cylinder grindings have been explained in connection with external and

internal cylinder grinders.

Types

Surface Grinder

These machines include the:

Belt grinder, which is usually used as a machining method to process metals and

other materials, with the aid of coated abrasives. Sanding is the machining of

wood; grinding is the common name for machining metals. Belt grinding is a

versatile process suitable for all kind of applications like finishing, deburring, and

stock removal.

Bench grinder, which usually has two wheels of different grain sizes for roughing

and finishing operations and is secured to a workbench or floor stand. Its uses

include shaping tool bits or various tools that need to be made or repaired. Bench

grinders are manually operated.
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Cylindrical grinder which includes the centerless grinder. A cylindrical grinder

may have multiple grinding wheels. The work piece is rotated and fed past the

wheel(s) to form a cylinder. It is used to make precision rods.

Surface grinder which includes the wash grinder. A surface grinder has a "head"

which is lowered, and the work piece is moved back and forth past the grinding

wheel on a table that has a permanent magnet for use with magnetic stock.

Surface grinders can be manually operated or have CNC controls.

Tool and cutter grinder and the D-bit grinder. These usually can perform the

minor function of the drill bit grinder, or other specialist tool room grinding

operations.

J ig grinder, which as the name implies, has a variety of uses when finishing jigs,

dies, and fixtures. Its primary function is in the realm of grinding holes and pins. Itcan also be used for complex surface grinding to finish work started on a mill.

Gear grinder, which is usually employed as the final machining process when

manufacturing a high precision gear. The primary function of these machines is

to remove the remaining few thousandths of an inch of material left by other

manufacturing methods (such as gashing or hobbing).
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Dr. M.G.R

EDUCATIONAL & RESEARCH INSTITUTE

UNIVERSITY

ADAYALAMPATTU, CHENNAI

COURSE NOTES

ENGINEERING GRAPHICS

PREPARED BY S.A.WILFRED RAJ KUMAR

LECTURER

DEPARTMENT OF MECHANICAL ENGINEERING

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