Production Engineering
(MET 351)
B.Tech. (6th Sem) Spring 2024
Department of Mechanical Engineering
NIT Srinagar
Course In-charge
Dr. Noor Zaman Khan
Course Outcomes
At the end of the course, a student should be able to:
• CO1: Determine the shear angle and cutting force in machining and understand the basics
of metal cutting.
• CO2: Estimate tool life and explain the tool wear mechanisms and abrasive machining
process.
• CO3: Analyze the forming process behavior for conventional and advanced metal forming
processes.
• CO4: Understand the basics of limits, fits and tolerances in manufacturing.
UNIT II
• Mechanisms of tool wear; Types of tool wear, Tool life: Variables
affecting tool life-Cutting conditions; Tool angles specification
systems; Tool materials; Desirable Properties of Cutting Tool;
Determination of tool life; Machinability, Economics of machining.
• Abrasive Machining Process: Introduction; Grinding: Characteristics
of a grinding wheel; Specification of grinding wheels; Mechanics of
grinding process; Grinding operations; Wheel wear; Surface Finish;
Selection of grinding wheels.
Tool life: Growth of flank wear for different speeds
• Using ℎ𝑓 = 0.3 mm as the tool life criterion, we note that the tool lives are
𝑇1 , 𝑇2 , and 𝑇3 .
• Also, it is obvious that a higher speed of cutting leads to a lower tool life.
• It has been experimentally established that the tool life equation is
• 𝑣𝑇 𝑛 = 𝐶
• Where, C and n are constants depending on the tool and work material,
tool geometry, and cutting conditions (except speed).
• Though cutting speed is the most dominant variable, the other cutting parameters, e.g., the uncut
thickness and width of cut, also affect the tool life.
• When machining is through the production of continuous chips without a built-up edge, the
generalized Taylor equation can be written as
• Where, 𝐶 ′ , n, p, q are constants. The units of v, T, t, and w are m/min, min, mm, and mm, respectively.
Cutting speed-tool life relation for different cutting tool materials
• Typical variation of tool life with speed for
HSS, WC, and ceramic tools, keeping the
other conditions the same.
• It is clear that the tool life for a given speed is
normally much higher with WC than that with
HSS.
• A ceramic tool performs better at a high
cutting speed.
Effect of tool geometry on tool life
•
Effect of tool geometry on tool life
• The rake and the clearance angles, also affect the
tool life.
• When the α increases, the tool life starts improving
because the cutting force reduces.
• A further increase in the α results in a larger
temperature since the tool becomes thinner and the
area available (Fig. a) for heat conduction reduces.
• When the clearance angle increases, the tool life
increases at first. This is due to the fact that for the
same volume of flank wear, ℎ𝑓 reduces (Fig. b).
• However, with a further increase in the clearance
angle, the tool becomes thinner and the tool life
decreases due to the higher temperature.
Numerical 2.1
• During machining of mild steel by carbide tool, the tool life is 30 min at a
cutting speed of 25 m/min. The tool life becomes 2 min, if the cutting
speed is increased 70 m/min. Estimate the tool life for this operation at a
cutting speed of 60 m/min.
Solution 2.1
• During machining of mild steel by carbide tool, the tool life is 30 min
at a cutting speed of 25 m/min. The tool life becomes 2 min, if the
cutting speed is increased 70 m/min. Estimate the tool life for this
operation at a cutting speed of 60 m/min.
n = 0.38, C = 91.0429, T = 2.99 = 3 min
Numerical 2.2
• During a metal cutting operation, the relationship between tool life and cutting speed is as
follows:
T1 = 120 min, 𝑣1 = 100 m/min
T2 = 50 min 𝑣2 = 130 m/min
Determine
(a) n
(b) tool life at v = 2.5 m/s
(c) cutting speed for tool life of 80 min.
Solution 2.2
• During a metal cutting operation, the relationship between tool life and cutting speed is as
follows:
T1 = 120 min, v1 = 100 m/min
T2 = 50 min v2 = 130 m/min
Determine
(a) n = 0.299, C = 418.48
(b) tool life at v = 2.5 m/s (T =
(c) cutting speed for tool life of 80 min. (v = 11247 m/min)
Cutting fluid
• The ways in which a cutting fluid affects machining can be summarized and classified as
follows:
1. Cooling down of the chip-tool-work zone by carrying away some of the generated heat.
2. Reducing the coefficient of friction at the chip-tool interface due to the formation of a
weaker compound at the interface.
3. Reducing the thermal distortion caused by temperature gradients generated during
machining.
4. Washing away the chips and clearing the machining zone.
5. Protecting the finished surface from corrosion.
• Cooling down obviously increases the tool life and reduces the thermal distortion.
• An ideal cutting fluid should
1. have a large specific heat and thermal conductivity,
2. have a low viscosity and small molecular size (to help rapid penetration to the chip-tool
interface),
3. be non-poisonous and noncorrosive,
