AProject Report

onTOOL LIFE OF HOB & BROACH

Under the Guidance of

Mr. Krishna Kumar(Chief Manager)

Mr. D.R. Singh(Deputy Manager)

Er. Neeraj Kumar Mishra

In

Scooters India Limited, Lucknow

Submitted by

Ashish GiriDeptt. of Mechanical EngineeringBundelkhand University, Jhansi

CONTENTS

Certificate

Acknowledgement

Vision Mission

Quality Policy

About Scooter India Ltd.

Products

Departments

About Machine Shop

About Line No. 7

Machine Used in Line No. 7

Manufactured Component of Line No. 7

Main Project

DECLARATION

I certify that Mr. Ashish Giri, a student of Institute of

Engineering & Technology, Bundelkhand University, Jhansi,

Mechanical Engineering II year has completed a project on "Tool Life

on Hob and Broach" under my guidance.

I certify the originality of the project report. I wish a bright

future for him.

Date : Mr. Krishna Kumar(Chief Manager)ManufacturingS.I.L. Lucknow

DECLARATION

I certify that Mr. Ashish Giri, a student of Institute of

Engineering & Technology, Bundelkhand University, Jhansi,

Mechanical Engineering II year has completed a project on "Tool Life

on Hob and Broach" under my guidance.

I certify the originality of the project report. I wish a bright

future for him.

Date : Mr. D.R. Singh(Deputy Manager)

ManufacturingS.I.L. Lucknow

ACKNOWLEDGEMENT

It is with great pleasure that I acknowledge the support of Mr.

Krishna Kumar (Chief Manager), Mr. D.R. Singh (Deputy Manager) and

Er. Neeraj Kumar Mishra, Machine Shops as well as the employees of

Machine Shop, Tool Room, Lab Room, Assembly Shop and Quality

Department.

To be thanked also are the machine operators and other factory

employees, who cooperated with me and made it sure that I learn

something from the operation that they are performing.

(Ashish Giri)

VISION OF THE ORGANISATION

To grow into global company constantly striving meet the

changing needs of customer through constantly improving existing

product adding new products and opting new technology and

expanding the customer base.

CORPORATE MISSION

To fulfill customer needs for economical and staff made of road

transport and quality engineering product through contemporary

technology.

QUALITY POLICY OF S.I.L.

We are committed to meet the customer requirements and

continuously improve our quality management system. The company

sales and services quality objective within the frame work of this

policy.

ABOUT SCOOTERS INDIA

Incorporated in 1972, Scooters India Limited is an ISO

9001:2000 and ISO 14001 Company, situated at 16 Km mile stone,

South-west of Lucknow, the capital of Uttar Pradesh on NH No 25 and

is well connected by road, rail and air.

It is a totally integrated automobile plant, engaged in designing,

developing, manufacturing and marketing a broad spectrum of

conventional and non-conventional fuel driven 3-wheelers.

Company’s plant owes its origin to M/s. Innocenti of Italy from

which it bought over the plant and machinery, design, documentation,

copyright etc. The company also possesses the world right of the

trade name LAMBRETTA / LAMBRO.

In 1975, company started its commercial production of Scooters

under the brand name of Vijai Super for domestic market and

Lambretta for overseas market. It added one more wheel to its

product range and introduced three wheelers under the brand name

of VIKRAM/LAMBRO. However, in 1997, strategically, the company

discontinued its two-wheeler production and concentrated only on

manufacturing and marketing of 3 wheelers. These three wheelers

have become more relevant in the present socio-economic

environment as it transports goods and passengers at least cost.

The company has its own marketing network of Regional Sales

Offices all over India, catering to customer’s requirements in the

areas of sales and services.

DESIGN AND DEVELOPMENT

DEPARTMENT

Design & Development has become the prime mover for the

organisation. The business today is customer driven. The department

remains in constant touch with the customers to transplant their

needs and thinking on the drawing board - nay on the computer

screen. The department serves the internal customers through

design, development, standardization, value engineering, defect

removal etc. Equipped with Computer Aided Design Laboratory ( CAD

lab ), Advanced Instrumentation, testing rigs prototype manufacturing

facilities and internet, the company's D & D is recognised by the

Ministry of Science and Technology, Govt. of India. It has the

distinction of the developing first zero pollution electric three wheeler

in the world. Company besides its own in-house R&D ; also works in

association with leading Research Associations & Educational

Institution like I.I.T 's. Kanpur; I.I.T. , Dehradun; A.R.A.I. Pune;

T.C.I.R.D. Patiala etc

Computer Aided Design Laboratory

The CAD laboratory provides a wide range of facilities. The

versatility of brains combines with the flavour of new creation to

evolve a quality product. All the designing & drafting process moulds

into a shape in this well-equipped environment of CAD

laboratory.Which includes FE analysis, Working model simulation &

designing through Auto-Cad 14.

ASSEMBLY DEPARTMENT

The components manufactured in plant as well as those bought

have to be finally assembled to make the product three wheelers. In

the process many sub assemblies, too, are involved. However, two

main assemblies worth mentioning are engine assembly and vehicle

assembly. Both are conveyorised. Every 5 minutes a three wheeler

rolls down the conveyor. The vehicle conveyor has 23 stations. Speed

can be adjusted to meet increasing demand.

DIE CASTING SHOP

The biggest die casting shop in this part of the country handles

both Aluminum and Zinc alloys. Equipped with pressure die casting

machines of 160, 250, 400 and 1,000 tons locking pressure, the metal

is fed to machines from individual holding furnaces of 75/150 kg.,

which in turn are fed by mother melting furnace of 500 kg. aluminum

capacity.

The shop based on projected area, is capable of producing

aluminum die casting upto 5 kg. in weight. The shop is backed by

chemical and metallurgical labs as also with a die maintenance

section. The well-equipped machineries are used in this department in

single shift, except two machines that are used in two shifts; that

produce all the accessories required by this organization. The die

casting of various type of components like Gear box housing,

Crantcase, Front wheel drum, Rear wheel drum, Bell housing,

Magneto flange, Cylinder head, lower and upper Handle bar, Levers,

Differential housing cover, Brake shoe etc are undertaken.

Die casting some components for fulfilling customers'

requirement are also taken up. Some of our customers are BHEL,

Bhopal; Greaves India Limited, Aurangabad to whom supplying the

Gear boxes and 422 cc aluminium Engine are supplied.

FABRICATION DEPARTMENT

The fabrication operations are carried out in Two departments viz. Press

Shop and Welding Shop. The Press Shop is equipped with 20 presses ranging

from 10 tons to 550 tons. Presses are fed by sheets cut to size on shearing

machines of 3000x6 & 2500x3 mm. size. Components ranging from washer to

cabin roof and door(1000x1200 mm.) are being processed in this shop.

The Welding Shop is equipped with battery of Spot welding, MIG welding,

Seam welding as well as Arc welding machines. CO2 welding is extensively used

for getting close tolerance on welded structures. The department has its own

auxillary shop for maintenance of tools and dies.

FOUNDRY LAB

The foundry, most modern in this part of the country, can

produce all grades of grey cast iron as well as S. G. iron. In fact, it had

been innovative to find new processes of modulisation, for which it

was granted 2 patents.Equipped with an Induction Melting furnace,

Shell Moulding Machines & Core Shooters, Green Sand Moulding

facilities, Isothermal Heat Treatment Furnace, one sand muller

machine, two shot blasting machine, two set jolting machines for

green sand moulding, fettling and shot blasting equipments, its

normal range of production weighs upto 8 Kgs. on a pattern plate of

450x600 mm. However, foundrymen are trained to make casting even

of 1 ton weight if emergent requirement arises.

The foundry is not fully loaded with its captive requirement.

Spare capacity is utilised for producing sophisticated castings of

prestigious customers like BHEL, Indian Railways, Aerospace, Brakes

India Limited, Crompton Greaves limited. The induction furnace has a

capacity of 1.3 tons. The two types of moulding is been done here. 1.

Shell moulding 2. Green sand moulding. The foundry can manufacture

a wide range of products namely Differential housing, Differential

cages, Power transimission wheel, Crankcase flange, Magneto motor,

Engine output flange, Adapter plate for electric vehicle, Cylinder for

both Vikram 410 petrol version and Vikram 750 diesel version.

ABOUT MACHINE SHOP

Machine shop has a wide variety of machines like General purpose

machine, Special purpose machine, Multispindle automatic machine,

Single spindle automatic machine etc; which are mainly working on

single shift through eight different lines. Line no 2 is basically

machining the aluminium components. crank shaft and cylinder

machining is usually done on line no 3. Line no. 4 is the Grinding line

where the grinding process is done. Heat treatment is performed in

line no 5, while different turning of shafts and gear shaping and

shaving are carried on line no 6.Line no. 7 includes the functioning of

gear manufacture process mainly broaching, hobbing, finish turning,

gear shaving etc. Machining of different levers, centreless grinding of

tubes and shafts, serration / thread rolling operations is achieved in

line no. 8 & lastly different components are fed in two other lines by

line no. 9. Blank turing of gear and machining of parts is done on

multi spindle and single spindle automatic machine. Engine

components and some vehicle component are the prime production

PAINT SHOP

Paint shop includes three sections namely Paints section, spray

phosphating section, pickling.Paint section includes two convention

painting spray booth & one electrostatic painting plant. The first one

is called conventional primer where mainly frame paintings are done.

The equipments used for conventional painting are Bullow's 230 spray

gun and pressure fit tanks (we prepare paints). The various types of

frames like Diesel 750, Mini petrol, Mini diesel, Diesel floor mounting,

Diesel Nepal, Diesel scrubber, Electric vehicle are painted here. The

other conventional booth is known as conventional finish booth. Here

the frame accessories like cabin front, roof top, front fork, axle

housing are painted. In electrostatic plant the accessories of the

frame, the component of lighter weight and minimum size like

silencer, pillar and various brackets are painted here.

In spray phosphating the main work is to clean the components

before painting or to make surface according to paint requirement.

After phosphating the products goes to passivation for converting

ferrous to ferric for paintings need. The products comes from welding

shop, press shop and machine shop to phosphating, and after the

process is being done the products go to vehicle assembly. The

pickling department is mainly for maintaining the surface of heavily

corroded materials.

TOOL ROOM

The tool room is a cell where brain combines with versatility to

evoke the new era of invention. The designs of tool coming from main

tool planning departments are implemented here. The tool room is

furnished with well equipped machineries namely, CNC machine

(Taiwan), Jig Boring machine (Czec Republic), Jig Grinding machine

(Switzerland), Profile Grinding machine (Germany), Die shielding

machine (Czech Republic), EDM (USA), Schaublin machine

(Switzerland).

Tool room evoke a high performance output, consisting almost

99.9% of company's requirement : one die casting die per year, 1-10

press tools per month, 8-10 jigs per month, 10-12 gauges per month

and 400 C.T. tools per monthThese machines are efficiently used to

manufacture different tools and dies like Jigs & fixture, Gauges,

Cutting tools, Forging dies, Die casting dies, Development items etc.

The different activities like like turning, milling different shapes,

grinding, heat treatment, jig boring, jig grinding, checking in the

standard room, heat treatment according to the job requirement, final

inspection are undertaken in the tool room.

DEPARTMENTS

The organisation has various departments to perform different

activities competently. SIL has an organised system to control

different activities. Personnel & administration department looks after

the employees welfare, medical benefits, conveyance facilities,

maintains their personal records and controls their regularity. It also

take care of the security for the organisation. Marketing & services

department looks after the marketing of the products, provide

services to the customer and regulates the activities in its various

regional offices.

Materials controls the purchasing of the raw material, keep an

eye on the cost of the material in the market, store the different

materials and products and establishes a company-vendor

relationship. Workshop manufacture different products in steps in

different lines. Design & development is the prime creative unit for

the organisation. It brings out some brilliant design with modern

technologies. Finance & accounts section keeps track on the financial

growth and the maintenance of various types of accounts.

PRODUCTS OF S.I.L.

Scooters India Limited makes various & versatile types of three

wheelers: Vikram 450D, Vikram 410G, Vikram 600G, Vikram 750D,

Vikram 750D (WC), Vikram EV.

The products have a high payload capacity and efficiency.

These are specially designed and developed for local transportation.

However, the generation of Vikram run successfully in different

countries also. Our product is very demanding in various countries all

over the world . Germany, Italy, Sudan, Nigeria, Nepal, Bangladesh

are few of the countries. For product details click on the product

options.

MACHINES USED IN LINE NO. 7

Broaching Machines

1. Internal Splines Broaching 4976

2. Oil groove broaching machine 3505

3. Bore Broaching 2021

4. Bore Broaching 3271

5. Bore Broaching 2997

Hobbing Machines

1. Semi Automatic Hobbing Machine – 10488

2. Semi Automatic Hobbing Machine – 10576

3. Semi Automatic Hobbing Machine – 10120

4. Tag Teeth Hobbing – 2014

5. Semi Automatic Hobbing Machine – 10290

6. Eight Head Shaft Hobbing Machine – 2586

7. Eight Head Shaft Hobbing Machine – 2585

Hydraulic Press & Turning Facing, Chamfering Machines

1. Fresh turning, facing & bore chamfering Machine – 2148

2. Hydraulic Press – 392

3. Fresh Turning, Facing & Bore Chamfering – 10489

4. Hydraulic Press – 728

5. Turning – 3249

6. Hydraulic Press – 2773

7. Turning – 296

8. Turning – 10498

9. Hydraulic Press – 383

10. Turning Machine – 10490

11. Turning Machine – 10387

Shaving Machines

1. Teeth Shaving – 4817

2. Teeth Shaving – 4102

3. Speed Gear Teeth Shaving – 4395

Milling Machines

1. Milling Machine – 10466

2. Horizontal Milling Machine – 2732

3. Horizontal Milling Machine – 10621

4. Cam Milling – 10388

5. Cam Milling – 91

6. Cam Milling – 513

7. Cam Milling – 511

Lathe Machine

1. Central Lathe Machine – 441

Drilling Machines

1. Portable Drilling Machine – 2419

2. Portable Drilling Machine – 5035

Teeth Chamfering Machine

1. Teeth Chamfering Machine – 2168

2. Teeth Chamfering Machine – 2992

3. Teeth Chamfering Machine – 10623

Bench Grinding Machine for Deburring

COMPONENTS MADE IN LINE NO. 7

1. Ring Nut

2. Speed Gears (I, II, III & IV)

3. Primary Transmission Wheel

4. Engine output Gear

5. Reverse Gears

6. Spline Sleeve

7. Transmission Shafts

8. Big Spockets

9. Couplings

10. Sliding Dog

11. Reverse Gear Sprockets

12. Central Lug

ABOUT LINE NO. 7

Broaching :-

Broaches tools for cutting metal, comprising a plain pilot

portion, a tapered toothed portion and a plain shank engaging with

the pulling head on a broaching machine. The teeth have normally

single cutting edges and on a circular broaches run in series round

the tapered portion, gradually increasing in cross section as they near

the shank. They are either pushed or pulled mechanically through a

previously cored or drilled round, square, rectangular or hexagonal

hole to produce the current form. They will also finish flat surfaces,

irregularity – formed holes and open grooves such as key ways in

hubs. Another application is to the forming of teeth in internal gears

and rachets, splines in shafts etc.

They are usually made of a tough, hard, sound, non distarting

steel alloy, high carbon and case hardening types, the precise steel

depending on the service life required, the material to be cut, and the

length and form of the broached areas. Relatively few are made of

case carburizing steel and hardened high speed steel is now the most

popular material for the cutting teeth of solid and some other

broaches. The tools have to be heat treated and ground and the heat

treatment is extremely important.

Broaches for finishing internal holes differ from those for

finishing the external surface of a component. Those to be pushed

through the work are shorter than those to be pulled through. For

internal work the tools are usually solid, unless their diameter is so

great as to render distortion in heat treatment probable and serious.

The teeth are of size and form for the operation and if the broach is

more than 3½ inches. How it is often made as a composite consisting

of a tough central portion of carbon steel, conically ground, on to

which cutting segments of nickel or high speed steel are mounted in

the form of toothed rings set one over the other until the cutting

portion is adequate for the job. This makes its possible tommorrow a

segment or ring when pulled or worm and insert a replacement each

ring then move up one this costs for less than replacing the entire

broach.

Hobbing :-

In this process, the gear bank is rolled with a rotating cutter

called hob. A majority of involute gears are produced by this

method. . A grear hob looks like a worm, but carries a number of

straight flutes (gashes), cut all around, parallel to its axis. This results

in the production of separate cutting teeth and cutting edges, as

shown. In operation, the hob is rotated at a suitable speed and fed

into the gear blank. The blank also rorates simultaneously. The

speeds of the two are so synchronised that the bank rotates through

one pitch distance for each complete revolution of the hob. There is

no intermittent motion of any of the two and the generating motion

continues steadily. The hob teeth are just like screw threads, i.e.

having a definite helix angle. The hob is, therefore titled to its own

helix angle while cutting the gear so that its teeth are square with the

blank and produce a true involute shape. Spur, helical and

herringbone gears and many other shapes like splines and gear

sprockets etc. can be cut by hobbing process.

Each cutting tooth of the hob is provided relief at its back to

enable clerance. In poration, the hob can be conceived as a cylindrical

body, around which the teeth of a long rack are wrapped along a

helical path and provided with straight flutes at regular intervals,

parallel to the axis of the cylinder. Cross section of every tooth across

the helix resembles that of the rack teeth.

Types of Hobbing :-

This hobbing process is classified into different types according

to the directions of feeding the hob for gear cutting. This classification

is as follows :

1. Hobbing with axial feed.

2. Hobbing with radical feed

3. Hobbing with tangential feed

Shaving :

It is a process of finishing gear teeth by running the gear at high

speed in mesh with a gear shaving tool which is in the form of a rack

or pinton. The teeth of the shaving tool are hardened, accurately

ground and their faces are provided with serrations. These serrations

form the cutting edges which actually provide a sort of scraping

operation on the mating faces of the gear teeth to be finished. The

gear is pressed into contact with the shaving tool and the latter

rotated at high speed. The gear also rotates in mesh with the tool and

is also reciprocated simultaneously. The shaving tool carries a little

inclined teeth so that their axes can be crossed as the two come in

contact. This prevents the jamming of the two. The above relative

motion of the gear and the shaving tool results in a highly finished

surface on the gear teeth. When a rack type tool is used, the gear is

mounted on a reciprocating arbor and is brought in mesh with a

horizontal rack situated under it. The rack is reciprocated

longitudinally at high speed and the gear across it. The lengthwise

movement of the rack type tool also rotates the gear. Shaving with

rack-type tool, however, suits only small gears. The shaving tools,

although costly, have a fairly long life.

Drilling :

Drilling is an operation through which holes are produced in a

solid metal by means of a revolving tool called drill. Since it is not

possible to produce a perfectly true hole by drilling, it is considered as

a roughing operation. Obviously, therefore, where a very close

dimensional accuracy is to be maintained, this forms only the basic

operation. For such holes, drilling is followed by another operation

called reaming, in which the required dimensional accuracy and fine

surface finish is obtained by means of a multi-tooth resolving tool

called reamer. Boring is the operation employed for enlarging an

existing hole. The hole may be previously drilled, cast, punched or

produced through any other suitable operation.

In line no. 7 there are portable drilling machine are used.

It is very small, compact and self-contained unit carrying a

small electric-motor inside it. It is very commonly used for drilling

holes in such components that cannot be transported to theshop due

to their size or weight or where lack of space does not permit their

transportation to the bigger type of drilling machine. In such cases,

the operation is performed on the site by means of the portable

electric drill. Portabe drills are fairly light in weight so that they can be

easily handled by one or two men only. They are manufactured in

different sizes and capacities, thus being suitable for a wide range of

hole sizes. Also, on account of the high speeds available, a

considerable saving in time is affected by their use. Another

advantage is that the holes can be drilled by means of them at any

desired inclination. Usually they are made to hold drills upto a

maximum diameter of 12 mm. However, portable drills of upto 18

mm. dia. capacity are available.

Milling :

‘Milling’ is the same given to the machining process in which

the removal of metal takes place due to the cutting action of a

revolving cutter when the work is fed past it. The revolving cutter is

held on a spindle or arbor and the work, clamped on the machine

table, fed part the same. In doing so, the teeth of the cutter remove

the metal, in the form of chips, for the surface of the work to produce

the desired shape.

Milling machine has acquired an indispensible position in all

modern production workshops. Its specific significance lies in its

capability to perform a large number of operations which no other

single machine tool can perform. At the same time, it gives

production at a fairly high rate and within very close machine tools

like shapers, planers, slotters etc., but for small and medium size

jobs only; as it will prove to be too slow for machining very long jobs.

For small and medium jobs, the milling machine gives probably the

fastest production with very high accuracy. For this reason, it has

gained a very wide application in mass production work. Obviously,

therefore, it is very versatile machine tool.

In line no. 7 there are horizontal milling machine are used. In

this the vertical coumn serves as a housing for electricals, the main

drive, spindle bearings, etc. The knee acts as a support for the saddle,

worktable and other accessories like indexing head, etc. Overarm

provides support for the yoke which in turn, supports the free end of

the arbor. The arbor carrying the cutter rotates about a horizontal

axis. The table can be given straight motions in three directions :

longitudinal, corss and vertical up and down but cannot be swivelled.

For giving vertical movement to the table the knee itself, together

with the whole unit above it, slides up and down along the ways

provided in front of the column. For giving cross movement to the

table, the saddle is moved towards or away from the column

alongwith the whole unit above it. A brace is employed to provide

additional support and rigidly to the arbor when a long arbox is used.

Both hand and power feeds can be employed for the work.

Cam Milling :

The constant rise and fall cams can easily be cut on a universal

milling machine, equipped with a universal dividing head and a

switching type vertical milling attachment. The dividing head is

geared to the tabe feed scre in the same way as for spiral milling. end

milling cutters are usualy employed in this operation. If the table is

moved towards right, the blank approaches nearer to the cutter. Also,

because of the gearing at the back, the dividing head spindle revolves

simultaneously. The combination of these two movements. i.e. the

table movement and the spindle rotation, enables milling of cam on

the blank fitted on the dividing head spindle. Both, the cutter as well

as the dividing head spindle, should be inclined at the same angle.

Steeper the angle of inclination quicker will be the approach of the

blank to the cutter. Alternatively, we can have the cam axis above

and the cutter axis below. In that case, we will be required to move

the table towards the left for feeding the blank against the cutter.

Plain Step And Fresh Turning Between Centers :

When the work is held between centers for any sort of turning

operation, one end (left hand end) is firmly gripped in a table dog and

then the same end is supported on the tip of the live centre. Tail of

the dog engages with the driving plate and the other end (right hand

end) of the job is supported on the dead centre fitted in the tail stock.

Work revolves during the operation and the tool is fed against the job.

Enough care should be taken while starting the operating, particularly

by a beginner. Speed of spindle and its direction of rotation should be

checked and suitably adjusted. Rough cuts in the beginning should be

followed by finishing cuts for which the spindle speed should be

increased and depth of cut reduced. Check the controls and practice

hand feeds which, in due course, can be followed by power feeds. For

taking any sort of measurement always stop the machine. In this first

the tail stock is moved and brought near the head stock to ensure a

true alignment of dead and live centers by sighting along the axes of

the two. Work is then held between centers and revolved. A chalk is

held in hand gently against the revolving work and marks made near

both the ends. Continuity of these marks indicates the trueness of the

marked centers, otherwise the chalk marks will be found only on

elevated portions of the periphery of the work.

Once the larger part of the excess material has been removed

through rough turning, it is followed by Finish turning operation in

order to bring the job to correct size and provide a fine surface finish

on it. The amount of excess material to be removed through this

operation is very less and, therefore, lighter feed and smaller depth of

cut are used and the heavier tool is replaced by a finish turning too.

Facing :

It is an operation which enables the production of a flat surface

through machining at the end of a job. In this operation the tool is fed

at right angles to the axis of the job. Since no longitudinal feed is

needed, the carriage is usually clamped to the bed so that it remains

stationary during the operation. Feed to the tool is provided by

moving the cross-slide by hand. Depending upon the diameter of the

work piece the power feed can also be used. Two methods of holding

the tools are usually employed. One is to set the tool slightly inclined

to the exact right angle position so that only the tip of the cutting

edge remains in contact with the job face and the remainder of the

tool is free of the job. Another method is to set the tool parallel to the

axis of the job. This is done when the job is held in a chuck or a face

plate. In both the cases the tool can either be fed outwards, i.e., away

from the centre. Normally the selection of any one to these methods

is according to convenience, still the latter method is more commonly

employed.

The facing operation is usually performed in two steps. In the

first step a rough facing operation is done by using a heavy cross of

the order of 0.5 to 0.7 mm and a deeper cut upto 5 mm (maximum).

It is followed by a finer cross feed of 0.1 to 0.3 mm and a smaller

depth of cut of about 0.5 mm. In the first step the idea is to remove

major part of excess material while in the second step a fine finish is

provided to the surface.

MAIN PROJECT

Tool life :

The time interval for which the tool works satifactory between

two successive grintings (sharpenings). Thus it can be basically

conceived as functional life of the tool. The tool is subjected to wear

continiauly while it is operating. Obviaulsy, after sometime, when the

tool wear is increased considerably, the tool losses its ablity to cut

efficiently & must be reground. If not it will totally fail. The tool life

can be effecting used as the basis to evaluate the performance of the

tool material assess machinbility of the conditions tool life :

(1) As time Period in minutes between two successive grintings.

(2) In terms of no of components machined between two

successive grindings. This mode is commonly used when the

tool operates continuously, as the case of automatic

machines.

(3) In terms of the volume of material removed between two

successive grindings this mode of expression is commonly

used when the tool is primarily used for heavy stock

removal.

Factors affecting tool life :

The life of cutting tool as affected by the following factors :

(1) Cutting speed

(2) Feed & depth of cut

(3) Tool Ceometry

(4) Tool material

(5) Work material

(6) Nature of cutting

(7) Rigidity of machine tool & work

(8) Use of cutting fluids

Effect of Cutting speed :

Out of all the above factors the max effect on tool life is of

cutting speed. The tool life is various inversely as the cutting speed

i.e. the higher cutting speed, the smaller the tool life. Generally the

reduction an tool life corresponding to an increase in cutting speed is

Parabolic.

V Tn =C

V= Cutting speed in m./min.

T= Tool life in min.

C= Machining constant

n= Tool life index

For all practical purpose the average values of exponent (n) for

common tool materials can be taken as :-

n = .1 to 0.15 for high speed steal tools

= 0.2 to 0.5 for cemented carbide tools

= 0.6 to 1.0 for ceramic tools