mt-ii

1. DEPARTMENT OF MECHANICAL ENGINEERING
ACADEMIC YEAR 2017 -2018 EVEN SEMESTER
ME6402 & Manufacturing Technology–II
UNIT TEST - I -ANSWER KEY
PART – A
1. Typesofcutting tool:
 Single point cutting tool
 Multipoint cutting tool
2. Tool signature:
The various angles of tools are mentioned in a numerical number in a particular order. This
order is known as tool signature.
3. Effectof rakeangleduringcutting:
Rake angle has a great effect on the cutting forces. Increasing and decreasing or keeping the rake
angle negative and positive, the cutting force and power increases and decreases respectively. A
higher value of rake angle weakens the cutting edge.
4. Chipthicknessratio:
The ratio of chip thickness before cutting to chip thickness after cutting is called chip thickness
ratio.
Chip thickness ratio, r = t1/t2
5. Tool life:
Tool life is defined as the time elapsed between two consecutive tool resharpening. During this
period, the tool serves effectively and efficiently.
6. Reasonfor lubricationisnotrequiredwhile machiningcastiron:
The high carbon content in cast iron is present in the form of graphite. It acts a self cooling agent
while machining the cast iron.

2. PART – B
7. (A) (i) Metal CuttingProcess:
 A cutting tool exerts compressive force on the work piece which stresses the work material
beyond the yield point and therefore metal deform plastically and shears off.
 Plastic flow takes place in a localized region called the shear plane.
 Sheared material begins to flow along the cutting toolface in the form of chips.
 Applied compressive force whichleads to formation of chips is called cutting force.
 Heat produced during shearing action raises the temperature of the work piece, cutting tool
and chips.
 Temperature rise in cutting toolsoftens and causes loss of keenness in cutting edge.
 Cutting force,heat and abrasive wear are important features in metal cutting.
(ii)Comparisonoforthogonal and obliquemetal cuttingprocesses:
Sl.No Orthogonal metal cutting Oblique metal cutting
1. Cutting edge of the tool is perpendicular
to the direction of tool travel.
The cutting edge is inclined at an angle less
than 90O to the direction of tool travel.
2. The direction of chip flow is
perpendicular to the cutting edge.
The chip flows on the tool face making an
angle.
3.
The chip coils in a tight flat
spiral The chip flowssideways in a long curl.
4.
For same feed and depth of cut the force
which shears the metal acts on smaller
areas. So the life of the toolis less.
The cutting force acts on larger area and so
tool life is more.
5. Produces sharp corners. Produces a chamfer at the end of the cut
6. Smaller length of cutting edge is in
contactwith the work.
For the same depth of cut greater length of
cutting edge is in contact withthe work.
7.
Generally parting off in lathe, broaching
and slotting operations are done in this
method.
This method of cutting is used in almost all
machining operations.

3. (B) Varioustypesofchipsproducedinmachiningprocess:
Chips are separated from the workpiece to impart the required size and shape. The chips
that are formed during metal cutting operations can be classified into three types:
a. Continuous chips:
 Chip is produced when there is low friction between the chip and tool face.
 This chip has the shape of long string or curls into a tight roll.
 Chip is produced when ductile materials such as Al, Cu, M.S, and wrought Iron are
machined.
 Formation of very lengthy chip is hazardous to the machining process and the
machine operators.
 It may wrap up on the cutting tool, workpiece and interrupt in the cutting operation.
 It becomes necessary to deform or break long continuous chips into small pieces.
 It is done by using chip breakers and this can be an integral part of the tool design or a
separate device.
b. Discontinuous or segmental chips:
 Chip is produced in the formof small pieces.
 These types of chips are obtained while machining brittle material like cast iron, brass
and bronze at very low speeds and high feeds.
 For brittle materials it is associated with fair surface finish, lower power consumption
and reasonable tool life.

4. c. Continuous chips with built-up edge:
 When high friction exists between chip and tool, the chip material welds itself to the tool
face.
 Welded material increases friction further which in turn leads to the building up a layer
upon layer of chip material.
 Build up edge grows and breaks down when it becomes unstable.
 Chips with build-up edge result in higher power consumption, poor surface finish and large
tool wear.
8. (A) (i) Tool Wear:
The various types of tool wears are,
a.Flank wear:
 Occursbetween tool and workpiece interface.
b.Crater wear:
 Due to pressure of the hot chip sliding up the face of the tool, crater or a
depression is formed on the faceof tool. (Ductilematerials)
 By diffusion shape of crater formed corresponds to the shape of underside of the
chip
c.Nose wear:
 Mechanical chipping of nose an cutting edge of the tool are commonly observed
causes fortool failure.
 This type of failure is pronounced in carbide tipped and diamond tools due to high
brittleness of tool material.

5. (ii)Cutting fluids:
Used to carry away the heat produced during machining.
Functions of cutting fluids:
 Cools the tool and workpiece
 Lubricates the cutting tool
 Reduces co-efficientof frictionbetween tool and workpiece
 Improves surface finish
 Causes the chip to break up into small pieces
 Washes away the chips from the tool
 Prevents corrosion of workand machine
Properties of cutting fluids:
 Should possess good lubricating properties
 Should have high heat absorbing capacity
 Should have high specific heat
 Should be odorless
 Should be non-corrosive
 Should have low viscosity
 Should be harmless
 Should not stain
 Should be economical
 Should be transparent
Types of cutting fluids:
 Water based cutting fluids
 Straight or heat oil based cutting fluids
 Mineral oils
 Straight fatty oils
 Mixed oils
 Sulphurised oils
 Chlorinated oils
Methods of applying cutting fluids:
 Flood under gravity
 Form of liquid jet

6. (B) Given:
V1=110m/min
T1=20min
V2=85m/min
T2=40min
Solution:
From Taylor’s tool life equation,
V1 (T1)n=V2 (T2)n
n=0.372…………………………………………….(ANS)
V1 (T1)n=C
C=335.26…………………………………………..(ANS)
95m/min speed,
T=29.66m/min…………………………………..(ANS)
For 30 min life,
V=94.6m/min……………………………………..(ANS)
PART – C
9. (A) CuttingTool Materials:
Selection of cutting tool material depends on
 Volume of production
 Tooldesign
 Type of machining process
 Physicaland chemical properties of work material
 Rigidity and condition of machine
Properties / Characteristics of cutting tool material
 Hot hardness
 Wear resistance
 Toughness
 Low friction
 Cost of tool
Types of tool materials:
a. Carbon toolsteel- with stand temperature up to 200oC
b. High Speed steel- withstand temperature up to 900oC
 18-4-1 high speed steel
 Molybdenum high speed steel
 Cobalt high speed steel

7. c. Cemented carbides- with stand temperature up to 1500oC
d. Ceramics- with stand temperature up to 1700oC
e. Diamonds- withstand temperature up to 1250oC
f. Cubic boron nitride- with stand temperature up to 1500oC
(b) Merchantcirclediagramofforces:
The followingassumptions are made by merchant to workout the force relations.
 The chip may be considered as a separate body held in equilibrium under the action of
twoequal, opposite and collinear resultant forces.i.e. F and F’
 The chip formation will be continuous without built up edge
 During cutting process, the cutting velocity remains constant.
 The cutting tool has a sharp cutting edge so that it does not make a flank contact with the
workpiece.