### ME2252-MANUFACTURING TECHNOLOGY II Two Marks Questions With Answers 2014

Anna University, Chennai

ME2252-MANUFACTURING TECHNOLOGY II

UNIT -1

THEORY OF METAL CUTTING

TWO MARKS QUESTIONS:

1. What is rake angle? What is the effect of nose radius in tools?

The angle between the tool face and the line parallel to the base of the tool is known as side rake angle. It is used to control chip flow.

2. What is tool?

The various angles of tools are mentioned in a numerical number in particular order. That is known as tool signature.

It is the joining of side and end cutting edges by means of small radius in order to increase the tool life and better surface finish on the work piece.

4. Name the factors that contribute to poor surface finish in cutting?

· Cutting speed

· Feed

· Depth of cut.

5. What is orthogonal cutting?

The cutting edge of tool is perpendicular to the work piece axis

6. Define oblique cutting?

Oblique cutting: - The cutting edge is inclined at an acute angle with normal to the cutting velocity vector is called oblique cutting process

7. What is cutting force?

The sheared material begins to flow along the cutting tool face in the form of small pieces . The compressive force applied to form the chip is called cutting force

8. What is chip reduction co-efficient ?

The reciprocal of chip thickness ratio is called chip reduction co-efficient.

K=1/r

9. What is the function of chip breakers?

The chip breakers are used to break the chips into small pieces for removal, safety and to prevent both the machine and work damage

10. Define machinability of metal?

Machinability is defined as the ease with which a material can be satisfactorily machined

11. How tool life is defined?

Tool life is defined as the time elapsed between two consecutive tool resharpening. During this period the tool serves effectively and efficiently

12. Write Taylor’s tool life equation?

n

Taylor’s tool life equation, VT =C

Where, V= Cutting speed in m/min.

T= Tool life in minute

C= Constant

N= Index depends upon tool and work.

13. What are the factors affecting tool life?

Cutting speed

Feed and depth of cut

Tool geomentry Tool material Cutting fluid Work material

Rigidity of work, tool and machine

14. What are the four important characteristics of materials used for cutting tools?

Hot hardness

Wear resistance

High thermal conductivity Resistance to thermal shock Easy to grind and sharpen .

Low mechanical and chemical affinity for the work material

15. Name the various cutting tool materials.

Carbon tool steel High speed steel Cemented carbides Ceramics Diamonds

16. What are the functions of cutting fluids?

It is used to cool the cutting tool and work piece.

It lubricates the cutting tool and thus reduces the co-efficient of friction between tool and work.

It improves the surface finish as stated earlier. It causes the chips to break up into small parts. It protects the finished surface from corrosion.

It washes away the chips from the tool. It prevents the tool from fouling. It prevents corrosion of work and machine

17. What are the factors responsible for built-up edge in cutting tools?

During cutting process, the interface temperature and pressure are quite high and also high friction between tool chip interfaces causes the chip material to weld itself to the tool face near the nose. This is called built up edge

18. List the essential characteristics of a cutting fluid?

It should have good lubricating properties to reduce frictional forces and to decrease the power consumption.

High heat absorbing capacity.

It should have a high specific heat, high heat conductivity and high film co- efficient.

High flash point.

It should be odorless

It should be non –corrosive to work and tool.

19. What are the causes of wear?

The tool is subjected to three important factors such as force, temperature and sliding action due tool.

20. Briefly, differentiate between orthogonal cutting and oblique cutting?

 Sl. No. Orthogonal cutting Oblique cutting 1. The cutting edge of the tool is perpendicular to the cutting velocity vector. The cutting edge is inclined at an acute angle with the normal to the cutting velocity vector 2. The chip flows over the tool face and the direction of chip-flow velocity is normal to the cutting edge. The chip flows on the tool face making an angel with the normal on the cutting edge. 3. The cutting edge clears the width of the work piece on either ends.(i.e No side flow) The cutting edge may or may not clear the width of the work piece. 4. The maximum chip thickness occurs at its middle. The maximum chip thickness may not occur at the middle.

21. Give two examples for orthogonal cutting.

Turning, facing, thread cutting and parting off

UNIT – 2

CENTRE LATHE AND SPECIAL PURPOSE LATHES

1. What is swing diameter?

The largest diameter of work that will revolve without touching the bed and is twice the height of the center measured from the bed of the lathe.

2. write the specifications of a typical lathe?

I, The length of bed.

ii, maximum distance between dead and live centres. iii, Types of bed( i,e) straight, semi gap or gap type. iv, The height of dead centres.

v, swing over the bed. vi, width of the bed. vii, spindle bore.

viii, spindle speed.

ix, H.P. of main motor and rpm. x, Number of spindle speeds.

xi, spindle nose diameter. xii, Feeds .

lathe centres, catch plates, carriers, chucks, mandrels and rests.

4. What are the operations can be performed on a lathe?

Turning, facing, forming, knurling, chamfering, thread cutting, drilling, boring, recessing, tapping, grooving etc.

5. Write down the names of any four lathe accessories?

lathe centres, catch plates, carriers, chucks, mandrels and rests.

6. What are the functions of feed rod and lead screw?

Feed rod:

It is used to guide the carriage in a straight line when it moves along the bed. Lead screw:

It is used to move the carriage while thread cutting operation is carried out. It also ensures the proper speed of work relative to the tool thread cutting operation.

7.Mention four types of chucks used in a machine shop?

i, Three jaw chuck (or) self centering chuck ii, Four jaw chuck (or) independent chuck. iii, magnetic chuck.

8. What is the application of Air operated chuck?

Heavy work piece are mounted with the help of air operated chucks because they will require more power to hold the work piece.

9. What is the purpose of mandrel? How many types of mandrels is there in common use?

Mandrels are used for holding hollow work pieces.

1. plain mandrel

2. collar mandrel

3. cone mandrel

4. special mandrel

5. step mandrel

6. Expansion mandrel

7. Gang mandrel

10. What is thread cutting operation?

Thread cutting is the operation of producing continues helical groove on a cylindrical work piece.

11.Name any four work holding devices?

1, collets

2, chucks

3, Fixtures

4, power chucks

Automatic machine or simply automats are machines tools in which all the operations required to finish off the work piece are done automatically with out the attention of an operator.

13. What are the advantages of automatic lathes?

a, Mass production of identical parts. b, High accuracy is maintained.

c, Time of production is minimized.

d, The bar stock is feed automatically.

UNIT – 3

OTHER MACHINE TOOLS

1. Compare hydraulic shaper with mechanical shaper?

 SL.NO Hydrulic shaper Mechanical shaper 1. 2. 3. 4. smooth cutting operation changing of cutting speed is easy Higher cutting to return ratio can be obtained Stroke length can be easily adjusted without stopping the machine Rough and noisy cutting operation changing of cutting speed is difficult Lower cutting to return ratio Change of stroke length is not possible with out stopping the machine.

2. Write down any four operations performed by a shaper?

Machining horizontal surfaces. Machining vertical surfaces. Machining inclined surfaces. Machining irregular surfaces.

3. Mention the operation performed by planer?

The following operations generally performed in a planer are a.Planning horizontal surface b.Planning vertical surface c.Planning curved surface d.Planning of an angle

4. What is the function of clapper block in a planer?

During cutting stroke, the tool block fits inside the clapper block rigidly. During the return stroke, the tool block lifts out of the clapper block to avoid rubbing of the tool on the job.

5. State the difference between a vertical shaper and a slotter?

 vertical shaper slotter 1. vertical shapers generally fitted with rotary table to machine curved surfaces 2. Rotary table along with tools will remove. 3. vertical shaper is not fixed in the vertical plane 1.The slides are fitted 2.slides will move to perform slotting. 3. slotter is fixed in the vertical plane.

6. What are the common work holding devices used on milling machines?

a.‘v’ blocks. b.machine vises. c.milling fixtures. d.Dividing heads

7. What is a shell mill?

A shell mill is a large type of face or end mill that mounts onto an arbor, rather than having an integral shank. Typicaly, there is a hollow or recess in the center of the shell for mounting hardware onto a separate arbor.

8. What is meant by up-milling and down milling?

In up milling, cutters rotates opposites to the direction of a feed of the work piece whereas in down milling, the cutter rotates in the same direction of travel of the workpiece.

9. What are the differences between up milling and down milling?

 SL.NO EVENT OF OPERATION UP MILLING DOWN MILLING 1. 2. 3. Direction of Travel Chip thickness cutting force Cutter rotates against the direction of travel of workpiece. Minimum at the beginning of cut Greeches max when the cut terminates. Increases from zero to max per tooth Cutter rotates in the same direction of travel of workpiece Maximum at the beginnining Greeches min at terminates Decreases from max to zero per tooth.

A thread milling has no chamfer. The mill is inserted into the hole along the axis of the spindle, deep enough to produce full thread depth required

11. write down the rule for gear ratio in differential indexing

Rule for gear ratio in differential indexing: Gear ratio = (A-N)/A

A- Selected no which can be indexed by plain indexing and approximately equal to N.

N- Required no. of divisions to be indexed.

12. How do specify radial drilling machine?

A drilling machine is specified by the job following items.

1. Maximum size of the drill in mm that the machine can be operate.

2. Table size of maximum dimension of a job can mount on a table in square meter.

3. maximum spindle speed and range of spindle speeds in r.p.m

13. Write down any four operations that can be performed in a drilling machine?

1. Drilling

2. counter sinking

3. Tapping

4. reaming.

14. What is meant by “sensitive hand feed”?

In drilling machines, manual sensing of the hand does feeding of the tools towards the work piece. it is called as sensitive hand feed

15. What is broaching?

Broaching is a process of machining a surface with a special multipoint cutting tool called “broach” which has successively higher cutting edges in a fixed path.

16. Why is sawing a commonly used process?

1. Easy handling of machines and spindle construction

2. Fast operation and cost of machinery is less

UNIT – 4

ABRASIVE PROCESSES AND GEAR CUTTING

1. What are the types of surfaces that could de produced using plain cylindrical grinders?

Plain cylindrical parts, cylindrical parts, cylinders, tapers, shoulders, fillets, cams, crankshaft etc.

2. State the abrasives sed in manufacture of grinding wheels?

a, corundum (75 to 90% crystalline Al2O3 +IRON OXIDE)

b, Diamond Artificial abrasives: a, Aluminium oxide b, silicon oxide

During the operation , the chips formed get entrapped in the linner granular space of abrasive particles. This is called loading.

The surface of the wheel becomes smooth and gets a glassy appearance. This is known as glazing wheel.

4. What is meant by dressing and truing?

Dressing is the process of loading and breaking away the glazed surface so that new sharp abrasive particles are again present to work for efficient cutting.

Truing is the process of trimming the cutting surface of the wheel to true with the axis.

5. Mention four important factors that influence the selection of grinding wheel?

1. constant factors

i. physical properties of material to be ground ii. Amount and rate of stock to be removed. iii. Area of contact.

iv. Type of grinding machine

2. variable Factors i.work speed.

ii. wheel speed.

iii. condition of the grinding machine iv. personal factor

6. What for lapping is used?

a, Removing small amounts of material from the surfaces of tools.

b, Removing small defects and surface cracks left during previous operations

c, Eliminating small distortion.

7. What is meant by honing?

An abrading process of finishing previously machined surfaces is known as honing.

8. What are the advantages of honing process?

1. Simple process which can be done on any general purpose machines such as lathes and drilling machines.

2. This process can be applied for both internal cylindrical and flat surfaces.

3. Honing enables the maximum stock removing capacity out of entire surface finishing operations.

9. What is meant by dressing and truing?

Dressing is the process of loading and breaking away the glazed surface so that new sharp abrasive particles are again present to work for efficient cutting.

Truing is the process of trimming the cutting surface of the wheel to run true with the axis.

10. What is roller burnishing process?

Roller burnishing is a method of cold working metal surfaces in which hardened sphere or cylindrical roller is pressed against the work to be processed. For example, in roller burnishing on a lathe, the burnishing tool is moved across the surface to be spanned.

UNIT – 5

CNC MACHINE TOOLS AND PART PROGRAMMING

1. Define NC?

Controlling a machine tool by means of a prepared program is known as numerical control or NC.

2. what are the classifications of NC machines?

1.point to point NC system

2. straight cut NC system

3.Contouring NC system

3. What are G-codes and M-codes? Give examples.

G-codes are preparatory function codes which prepare the machine are for different modes of movement like positioning, contouring, thread cutting etc.

Eg. G00 – Point to point positioning

G01 – linear interpolation

M- codes are miscellaneous function codes which denote the auxillary or switching information such as coolant on/off, spindle speed etc.

Eg. M00 – Program stop

M01 – Optional stop.

4. What is the role of computer for NC machine tool?

computer numerical control is an NC system that utilizes stored program to perform basic numerical control functions. mini or micro computer based controller unit is used.

5. Name the various elements of CNC machines?

2.Mini computer

3. servos and interface logic

4. Motion feedback

6. What is the role of computer for NC machine tool?

computer numerical control is an NC system that utilizes stored program to perform basic numerical control functions. mini or micro computer based controller unit is used.

7.What is point –to- point (PTP) system?

It is also called positioning system. The objectives of the machine tool control is to move the cutting tool to a predefined location. The speed or path is not important in this system

8. Mention the main differencebetween CNC and DNC?

CNC system can do operations on only one machine at a time. But direct numerical control involves that at a time a large central computer to direct the operations of a number of separate NC machines

9. List the commonly used co – ordinate system of CNC machine tools?

Cantilever construction Bridge construction Column construction Gantry construction

10. What is the difference between incremental and absolute system?

In absolute programming, the distance at my point at any instant will be measured from the origin ( X=0, Y=0).

Whereas in incremental programming, the instant point will be noted as (X=0,Y=0). Further measurement will be made from the particular point only.

11. Write down the types of statements in APT language.?

1. Geometric statements

2. Motion statements

3. postprocessor statement

4. special control or Auxiliary statements

12. Define subroutine?

If the same machining operations, which was carried out already, is to be performed at many different positions on the work piece, it can be executed by means of a program called as subroutines