This document discusses the mechanics of cutting metal. It defines key terms like rake angle, shear angle, chip thickness, cutting ratio, and cutting forces. It also outlines assumptions made in analyzing the cutting process, such as orthogonal cutting and plastic deformation through shear on the shear plane. Equations are provided for chip velocity, shear strain rate, cutting forces, friction coefficient, and stresses on the shear plane.

1. Mechanics of Cutting
Mahfudz Al Huda Magister Teknik Mesin Univ. Pancasila, 2010 1
  



  
cos
sin
,
1 sin
cos
Cutting ratio, tan
c
o
t
t
r
-r α
r α
  
 

 
   
   

45
2 2
45
tan
Shear angle predictions :
Velocities, Vc 
V sin
cos 
r = cutting ratio
t0 = depth of cut, mm
tc = the chip thickness, mm
 = shear angle, 
 = rake angle, 
 = coefficient of friction
 = friction angle, 
V = cutting speed, m/min
Vc = the velocity of the chip, m/min

2. Cutting Mechanisms
Mahfudz Al Huda
Magister Teknik Mesin Univ. Pancasila, 2010
2
Asumsi-2 dlm membahas cutting mechanism:
•Proses pemotongan adl orthogonal cutting.
•Tool Speed, VT = 0
•Workpiece Speed = Cutting Speed = V
•Benda kerja terpotong krn terjadi deformasi plastis berupa slip pd bidang geser (shear plane) akibat tekanan geser (shear stress).
•Slip terjadi secara teratur pd lapisan tipis geram dg tebal X dan bergeser sejauh S, maka regangan geser (shear strain): dimana : shear angle, : rake angle.
•Chip speed VC, dan Shear speed VS:
•Shear strain speed:
•Cutting ratio: t1 & t2: tebal geram sebelum dan sesudah dipotong
•Cutting force R: FH & FV: gaya potong horizontal & vertical, dpt diperoleh dg mengukur gaya tsb menggunakan strain gauge atau tool dynamometer.
Tool
Tool
Workpiece
Workpiece

3. Cutting Mechanisms
Mahfudz Al Huda
Magister Teknik Mesin Univ. Pancasila, 2010
3
•Koefisien gesek (friction coefficient) pd rake face: : friction angle, F& N: gaya gesek & gaya normal pd rake face.
•Gaya-gaya pd bidang geser (shear plane): FS & FN: gaya geser (shear force) & normal pd shear plane.
•Sudut geser (shear angle) : shg sudut geser dpt dihitung dg mengukur tebal geram sebelum dan sesudah pemotongan dan rake angle.
•Gaya-gaya pada rake face:
•Tegangan geser (shear strain) pd shear plane: dimana AS: luas bidang geser, b: cutting width, S & S: tegangan geser (shear stress) & tegangan normal (normal stress) pd bidang geser.