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Tech 3113Manufacturing Tooling
Nageswara Rao Posinasetti
05/03/2023Nageswara Rao Posinasetti 1
3B Cutting Tool Design
05/03/2023Nageswara Rao Posinasetti 2
Cutting Tool Materials Required properties
Higher hardness Hot hardness Wear resistance Toughness Low friction Better thermal characteristics
May 3, 2023(c) TMH New Delhi, Manufacturing Technology Vol 2,Metal Cutting and
Machine Tools by P N Rao3
Carbon Tool Steels These are essentially plain carbon
steels with carbon percentages between 0.6 to 1.5% and some very small alloy additions such as Manganese, Silicon, Tungsten, Molybdenum, Chromium and Vanadium.
Beyond 200C (392F ) they loose their hardness and cease to cut.
May 3, 20234
High Speed Steel This class of tool materials have significant
quantities of tungsten, molybdenum, chromium and vanadium.
The complex carbides of tungsten, molybdenum and chromium distributed through out the metal matrix provide very good hot hardness and abrasion resistance.
For the same hardness, less amount of molybdenum (compared to Tungsten) needs to be added, however more care need to be exercised in hardening as decarburizing takes place in molybdenum steels.
May 3, 20235
High Speed Steel The main advantages of high speed
steels is in their high hardness, hot hardness, good wear resistance, high toughness and reasonable cost.
Toughness of high speed steels is highest among all the cutting tool materials.
May 3, 20236
Cemented Carbides Cemented carbides are produced by
the cold compaction of the tungsten carbide powder in a binder such as cobalt, followed by liquid-phase sintering.
High hot hardness. Higher Young's modulus. Carbides are more brittle and
expensiveMay 3, 20237
Cemented Carbides The usual composition of the straight
grade carbides is 6 wt% Co and 94 wt% WC with the cobalt composition ranging from 5 to 12 wt%.
Addition of titanium carbide (TiC) increases the hot hardness, wear resistance, and resistance to thermal deformation, but decreases the strength. The usual composition is about 5–25 wt%. May 3, 20238
Cemented Carbides Choose a grade with the lowest cobalt content
and the finest grain size consistent with adequate strength to eliminate chipping.
Use straight WC grades if cratering, seizure or galling are not experienced in case of work materials other than steels.
To reduce cratering and abrasive wear when machining steel, use grades containing TiC.
For heavy cuts in steel where high temperature and high pressure use a multi-carbide grade containing W-Ti-Ta and/or lower binder content.
May 3, 20239
Cemented Carbides Cemented carbides being expensive are
available in insert form in different shapes such as triangle, square, diamond, and round.
Each of the edge would act as a cutting edge. As seen from the Fig 2.26, the tool bit is
made of tungsten carbide, while the tool holder shank is made from alloy steel to provide the necessary strength and reduce the total cost.
May 3, 202310
May 3, 202311
Coated Carbides Several coatings and coating methods have
been developed for cutting tools. Since late 60's thin (about 5 m) coating of TiN
has been used on cemented carbide tools. Ceramic coatings used are hard materials and
therefore provide a good abrasion resistance. They also have excellent high temperature
properties such as high resistance to diffusion wear, superior oxidation wear resistance, and high hot hardness.
May 3, 202312
May 3, 202313
Cemented Carbides Choose a grade with the lowest cobalt content
and the finest grain size consistent with adequate strength to eliminate chipping.
Use straight WC grades if cratering, seizure or galling are not experienced in case of work materials other than steels.
To reduce cratering and abrasive wear when machining steel, use grades containing TiC.
For heavy cuts in steel where high temperature and high pressure deform the cutting edge plastically, use a multi carbide grade containing W-Ti-Ta and/or lower binder content.
Ceramics Ceramics are essentially alumina (Al2O3) based
high refractory materials introduced specifically for high speed machining of difficult to machine materials and cast iron.
These can withstand very high temperatures, chemically more stable and have higher wear resistance than the other cutting tool materials.
The main problems of ceramic tools are their low strength, poor thermal characteristics and the tendency to chipping.
May 3, 202314
May 3, 202315
Ceramics Use the highest cutting speed recommended and
preferably select square or round inserts with large nose radius.
Use rigid machine with high spindle speeds and safe clamping angle.
Machine rigid workpieces. Ensure adequate and uninterrupted power supply. Use negative rake angles so that less force is
applied directly to the ceramic tip. The overhang of the tool holder should be kept to
a minimum; not more than 1.5 times the shank thickness.
May 3, 202316
Ceramics Large nose radius and side cutting edge angle on
the ceramic insert to reduce the tendency of chipping.
Always take a deeper cut with a light feed rather than a light cut with heavy feed; ceramic tips are capable of cuts as deep as one-half the width of the cutting surface on the insert.
Avoid coolants with aluminium oxide based ceramics.
Review machining sequence while converting to ceramics and if possible introduce chamfer or reduce feed rate at entry.
Diamond Diamond is the hardest known (Knoop hardness ~
8000 kg/mm2) material that can be used as a cutting tool material.
It has most of the desirable properties of a cutting tool material such as high hardness, good thermal conductivity, low friction, non-adherence to most materials, and good wear resistance.
Artificial diamonds which are basically polycrystalline (PCD) in nature. These are extensively used in industrial application because they can be formed for any given shape with a substrate of cemented carbide.
May 3, 202317
May 3, 2023Rao P N18
Cutting Tool MaterialsCarbon steels
Low strength, softer materials, non ferrous alloys, plastics
Low cutting speeds, low strength materials
May 3, 2023Rao P N19
Cutting Tool MaterialsCarbon steels
Low strength, softer materials, non ferrous alloys, plastics
Low cutting speeds, low strength materials
HSS All materials of low and medium strength and hardness
Low to medium cutting speeds, low to medium strength materials
May 3, 2023Rao P N20
Cutting Tool MaterialsCarbon steels
Low strength, softer materials, non ferrous alloys, plastics
Low cutting speeds, low strength materials
HSS All materials of low and medium strength and hardness
Low to medium cutting speeds, low to medium strength materials
Cemented carbides
All materials upto medium strength and hardness
Not suitable for low speed application
May 3, 2023Rao P N21
Cutting Tool MaterialsCarbon steels
Low strength, softer materials, non ferrous alloys, plastics
Low cutting speeds, low strength materials
HSS All materials of low and medium strength and hardness
Low to medium cutting speeds, low to medium strength materials
Cemented carbides
All materials upto medium strength and hardness
Not suitable for low speed application
Ceramics Cast iron, Ni-base super alloys, non ferrous alloys, plastics
Not for low speed operation or interrupted cutting. Not for machining Al, Ti alloys.
Rigidity Strength Weak links Force limitations Speed, feed and size Related force components Chip disposal Uneven motions Chatter
05/03/2023Nageswara Rao Posinasetti 22
Guidelines for Cutting tool Design
Back rake angle Side rake angle End relief angle Side relief angle End cutting edge angle Side cutting edge angle Nose radius
05/03/2023Nageswara Rao Posinasetti 23
Basic tool angles (Tool Signature)
Establish the operating conditions Select the
Cemented carbide grade Nose radius Insert shape Insert size Insert thickness Tool style Rake angle Shank size Chip breaker
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Selecting carbide Tools
Feed, speed and depth of cut greatly influence the machining performance.
Also lead angle affects the performance
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Establish the operating conditions
Increase the speed Decrease the feed and/or depth of
cut Change to a tougher grade carbide
insert Use a negative rake Hone the cutting edge before use Check the rigidity and tool overhang
05/03/2023Nageswara Rao Posinasetti 26
To reduce cutting edge chipping
Select the cemented carbide gradeStraight carbides - Tungsten carbide (WC) and cobalt binder
Cast iron, nonferrous and nonmetallic materials
Resistance to edge wear
05/03/2023Nageswara Rao Posinasetti 27
Select the cemented carbide gradeStraight carbides - Tungsten carbide (WC) and cobalt binder
Cast iron, nonferrous and nonmetallic materials
Resistance to edge wear
WC + Titanium carbide + Tantalum carbide with cobalt binder
Steels Resistance to cratering
Coated carbides
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05/03/2023Nageswara Rao Posinasetti 29
Based on surface finish
05/03/2023Nageswara Rao Posinasetti 30
Select the nose radius
Round – strong and large radius, good for higher feed rates
Square – medium stronger Traingular – least stronger, less
number of cutting edges, but more versatile in use
05/03/2023Nageswara Rao Posinasetti 31
Select the insert shape
05/03/2023Nageswara Rao Posinasetti 32
Smallest size based on the depth of cut used
Cutting edge should be 1.5 times that of the length of cutting edge engagement.
05/03/2023Nageswara Rao Posinasetti 33
Select the insert size
Gives the strength of the tool
05/03/2023Nageswara Rao Posinasetti 34
Select the insert thickness
Based on the geometry of the operation to be performed.
05/03/2023Nageswara Rao Posinasetti 35
Select the tool style
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Select the Rake Angle
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Select the Shank Size
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Select the Chip Breaker
05/03/2023Nageswara Rao Posinasetti 39
Tool Holder Identification
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Carbide Insert Identification
05/03/2023Nageswara Rao Posinasetti 41
Drilling Reaming Milling Gear cutting
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Multiple-Point Cutting Tools
05/03/2023Nageswara Rao Posinasetti 43
d = drill diameter, in f = feed in/rev This is valid for alloy steel 200
BHN
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Power requirement for Drilling8.18.0200,25, dfMTorque
28.08.0 625500,57, ddfTThrust
05/03/2023Nageswara Rao Posinasetti 45
Power requirement for Reaming
2.01
21
8.18.0
1
1300,23
dddd
dfkM
2.01
1
8.08.0
1
1600,42
dddd
dfkT
d1 = reamer diameter, in.
f = feed in/rev
k = constant based on number of flutes, See Table 3-11.
Power in HP
M = tool torque, in-lb N = speed, rpm Power in Watts = Hp * 746
05/03/2023Nageswara Rao Posinasetti 46
Power
025,63NMPc
Depends on the material removal rate
Uses empirical equations developed based on experiments
See Machinery’s Handbook pp 1052 – 1062 (28th Edition)
05/03/2023Nageswara Rao Posinasetti 47
Machining Power
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Pc = KpCQW
Pc = power at the cutting tool
Pm = power at the motor
Kp = power constant (see tab 24, 25 and 30)
Q = metal removal rate (tab 29)
EWQCK
EPP pc
m
DRILLING
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05/03/2023Nageswara Rao Posinasetti 50
For Inch units only:
T = 2 kd Ff Ft B W + kd d2 J W
M = Kd Ff FM A W
Pc = MN/63,025
T = Thrust; lb or N
M = Torque; in-lb or N.m
N = Spindle rpm
05/03/2023Nageswara Rao Posinasetti 51