To understand merchant cutting force diagram To learn various sources of heat in metal cutting

1. Manufacturing Processes-2
SUBJECT CODE :4ME04
SEM 4
DEPARTMENT OF MECHANICAL ENGINEERING

2. BY MR.K.P.PAWAR
LECTURER
ANURADHA COLLEGE OF ENGINEERING
*

3. LECTURE -4
Objectives of Lecture
 To understand merchant cutting force diagram
 To learn various sources of heat in metal cutting

4. Merchant cutting force diagram
Assumptions:
1.The cutting velocity always remains constant
2. Cutting edge of the tool remain sharp throughout the cutting
3. There is no side ways of flow of the chip
4. Only continuous chip is produced
5.There is no built-up edge
6. No consideration is made of the inertia force of the chip
7. The behavior of the chip is like that of a free body which is in
the state of stable equilibrium under the action of two resultant
forces which are equal, opposite & collinear

5. Fs = Shear force, which acts along the
shear plane, is the resistance to shear of
the metal in forming the chip
Fn = Force acting normal to the shear
plane ,is the backing up force on the
chip provided by the work piece
F = Frictional resistance of the tool
acting against the motion of the chip as
it moves upward along the tool
N = Normal to the chip force, is
provided by the tool
Fc = Horizontal cutting force exerted by
the tool on the work piece
Ft = Vertical force which helps in
holding the tool in position and acts on
the tool nose

7. 1. Merchant circle is useful to determine the relation between the
various forces & angles.
2. In the diagram two force triangles have been combined & R &
R’ together have been replaced by R
3. The force R can be resolved into two components Fc & Ft
4. Fc & Ft can be determined by force dynamometers
5. The rack angle (α ) can be measured from the tool & forces F &
N can then be determined
6. The shear angle (Ф) can be obtained from it’s relation with chip
reduction coefficient
7. Now Fs & Fn can also be determine

8. Relationship of various forces
F=OA=CB=CG+GB
=ED+GB
=Fc sin 훼 + Ft cos 훼
N=AB=OD-CD
=OD-GE
=Fc cos 훼 + Ft sinα
Frictional force diagram

9. Shear Force System
Fs = OA=OB-AB
=OB-CD
= Fc cosФ – Ft sinФ
Fn = AE= AD+DE
=BC + DE
= Fc sinФ + Ft cosФ

10. Ф

11. Sources of Heat in Metal Cutting

13. Around shear Plane
 Region in which actual plastic deformation of the metal occurs
during machining.
 Due to this deformation heat is generated.
 Portion of this heat is carried away by the chip, due to which
it’s temperature is raised.
 The rest of the heat is retained by the work piece.
 Region is known as primary deformation zone.

14. Tool- chip interface
 As the chip slides upwards along face of the tool friction occurs
between their surfaces, due to which heat is generated.
 A part of this heat carried by the chip, which further raises the
temperature of the chip and the rest transferred to the tool & the
coolant.
 This area is known as secondary deformation zone.
 The amount of heat generated due to friction increases with the
increase in cutting speed.
 It is not appreciably effected with the increase in depth of cut.
 When the feed rate is increased the amount of frictional heat
generated is relatively low. But, in that case,the surface finish
obtained is inferior

15. Tool- work piece interface
 That portion of tool flank which rubs against the work surface
is another source of heat generation due to friction.
 This heat is also shared by the tool, work piece and the coolant
used.
 It is more pronounced when the tool is not sufficiently sharp.

16. Question & Answer Session
Q.1 .What are various assumptions assume by merchant for
cutting force analysis ?
Q.3.What are various sources of heat in metal cutting ?