Chapter1 Basic knowledge in the metal cutting process

Chapter2 Manufacture
processing Equipment
Section1 Basic knowledge in
the metal cutting process
Section1 Basic knowledge in the metal
cutting process
• 2.1.1 Basic definition
1 、Cutting motion and cutting regime
2、 Essential definition for the working parts of cutting tools
3 、Conversion of tool angles
4 、Working angles for cutting tool
5 、Parameters of the cutting layer and cutting mode
2.1.1 Basic definition
• The process in which the excess metal on
a blank is cut off by a cutting tool, and formed
into a required part, is called metal cutting.
1、 Cutting motion and cutting regime
(1) Cutting motion
1)Main motion
2)Feeding motion
3)Combination of cutting motions and combined speed
Figure2-1 Cutting motion in turning
Figure2-2 Cutting motions in planning, drilling, milling
Figure2-3 Combination of cutting motions
(2)Three elements of cutting regime
1)Cutting speed
2)Feeding speed, feed and feed per tooth
3)Back engagement of the cutting edge
2、 Essential definition for the working
parts of cutting tools
(1)Structure elements for the working part of cutting
1)Rake face
3)Cutting edge
4)Tool nose
Figure2-4 Working part of typical turning tool
(2)Reference system for the marked
angles of cutting tools
1)Tool reference plane
2) Tool cutting edge plane
3)Predetermine condition for motion
4)Predetermine condition for setup
5) Main section and main section reference system
6)Normal section and normal section reference system
7)Transverse section, longitudinal section,
transverse section or longitudinal section system
Figure2-5 Main section and normal section Figure2-6 Transverse section and longitudinal
reference system
section reference system
(3)Reference system for the working angles
of cutting tools
Figure2-7 Working angles of cutting tool
(4) Marked angles of the cutting
1)Rake angle
2)Clearance angle
3)Cutting edge angle
4)Minor cutting edge angle
5)Tool cutting edge inclination angle
Figure2-8 Nominal angles of cutting tool in main section reference system
3 、Conversion of tool angles
Figure2-9 Conversion of tool angles between in main section and in normal section
4、 Working angles for cutting tool
(1)Influence of feeding motion on working angle
1)Transverse turning
2)Longitudinal turning
(2) Influence of setup for cutting tool on working angle
1)Influence of locating position for tool nose on working angle
2)Influence of the direction for the center line of the tool bar
on working angles
Figure2-10 Influence of transverse feeding motion
Figure2-11 Working angles in turning
Figure2-12 Influence of locating position for
tool nose on working angles
5、 Parameters of the cutting layer
(1)Cutting layer
1) Undeformed chip thickness
2)Width of uncut chip
3)Cross-sectional area of uncut chip
(2) Cutting mode
Figure2-13 Parameters of the cutting layer in longitudinal turning
Section1 Basic knowledge in the metal
cutting process
2.1.2 cutting tool materials
• 1、 Performance for cutting tool materials
• 2 、Frequently-used cutting tool materials
• 3 、Other tool materials
1 、Performance for cutting tool materials
(1)High hardness and wear –resistance
(2)Sufficient strength and toughness
(3)High heat resistance
(4)Good technological properties
(5)Good economy conditions
2 、Frequently-used cutting tool materials
At present, the most commonly used of
cutting materials are high-speed steels
and carbide alloys. Carbon tool steels
such as T10A, T20A, alloy tool steels such
as 9SiCr, CrWMn, are only used in some
hand tools or cutting tools working at low
cutting speed, due to their poor heat
(1) High-speed steels
• There are high alloy tool steels having more tungsten,
molybdenum, chromium, vanadium etc elements so that
these possess higher heat resistance and strength,
toughness as well wear resistance, can work from
500~650 ℃. Due to their good technological properties
these are the main material of complex tools, such as
drills, formed cutters, broaches, gear cutting tools
etc .According to applications, high-speed steels can be
divided into plain high-speed steels and high property
high-speed steels, and melting high-speed steels and
powder metallurgic high-speed steels according to its
manufacture technology.
(2)Carbide alloys
The carbide alloys are made of metallic
carbide powder (WC, TiC, etc.) and bonding
mediums (Co, Mo, Ni) through powder
metallurgy. It is usually referred to as sintered
carbide and sometimes it is called cemented
The performances of carbide alloys are decided by the
varieties, properties, content and grain size of the carbides, and
the content of bonding medium. The higher the carbide content
in carbide alloys, the higher the hardness of carbide alloys but
the lower the bending strength of carbide alloys. When the
content of the bonding medium is higher, the status reverses. In
general, carbide alloys posses high hardness, wear-resistance
and heat –resistance because they mainly consist of metallic
carbides with high melting point and hardness, good chemical
stability and heat stability. The cutting temperature for carbide
alloys reaches up to 800~1000℃, therefore, the chief
advantages of carbide are its ability to remove metal much faster
(higher cutting speeds) and it required less frequent sharpening.
The disadvantages of carbide alloys are mainly their poor
bending strength and impact toughness so thy are not suitable
for heavy cutting or for intermittent cutting.
3 、other tool materials
(1)Coated tools
(4)Cubic boron nitride (CBN)
Section4 Machine tools and machining
2.4.1 Generating Motion of Machine Tools
2.4.2 Engine Lathes
2.4.3 Turret lathes
2.4.4 CNC turning centers
2.4.1 generating motion of machine tools
Machining is the most versatile and accurate of
all manufacturing processes in its capability to
produce a diversity of part geometries and
geometric features (e. g., screw threads, gear
teeth, flat surfaces). Casting can also produce a
variety of shapes, but it lacks the precision and
accuracy of machining. The principle used in all
machine tools is one of generating the surface
required by providing suitable relative motions
between the cutting tool and the workpiece.
Fig2-14 Generating shapes in machining
(a) Straight turning; (b) Taper turning; (c) Contour turning;
(d) Plain milling; (e) Profile milling
Fig2-15 Forming to create shape in machining
(a) Form turning; (b) Drilling; (c) Broaching
Fig2-16 Combination of forming and generating
to create shape
(a) Thread cutting on lathe; (b) Slot milling
2.4.2 Engine Lathes
• The oldest and most common machine tool is
the lathe, which removes material by rotating the
workpiece against a single-point cutter. Lathes
used in manufacturing can be classified as
speed lathes, engine lathe, toolroom lathes,
turret lathes, automatic lathes, tracer lathes, and
numerical control turning centers.
• Turning processes are very versatile. The
following processes are capable of producing a
wide variety of shapes illustrated in Fig.4-7:
• (a) Facing-The tool is fed radially into the rotating work on one end
to produce a flat surface on the other end.
• (b) Taper turning-Instead of feeding the tool parallel to the axis of
rotation of the work, the tool is fed at an angle, thus creating a
tapered cylinder or conical shape.
• (c) Contour turning-Instead of feeding the tool along a straight line
parallel to the axis of rotation as in turning, the tool follows a contour
that is other than straight, thus creating a contoured from in turned
• (d) Form turning-In this operation, sometimes called forming, the
tool has a shape that is imparted to the work by plunging the tool
radially into the work.
• (e) Chamfering-The cutting edge of the tool is used to cut an angle
on the corner of the cylinder, forming what is called a “chamfer”.
• (f) Cutoff-The tool is fed radially into the rotating work at some
location along its length to cut off the end of the part. This operation
is sometimes referred to as parting.
• (g) Threading-A pointed tool is fed linearly across the
outside surface of the rotating work part in a direction parallel
to the axis of rotation at a large effective feed rate, thus
creating threads in the cylinder.
• (h) Boring-A single-point tool is fed linearly, parallel to the
axis of rotation, on the inside diameter of an existing hole in
the part.
• (i) Drilling-Drilling can be performed on a lathe by feeding
the drill into the rotating work along its axis. Reaming can be
performed in a similar way.
• (j) Knurling-This is not a machining operation because it
does not involve cutting of material. Instead, it is a metal
forming operation used to produce a regular cross-hatched
pattern in the work surface.
Fig2-17 Engine lathe
Fig2-18 Friction clutch
Fig2-19 Manipulation Mechanism
Fig2-20 Spindle Assembly
2.4.3 Turret lathes
• Turret lathes are a major departure from engine or basic lathes.
These machines possess special features that adapt them to
production. The “skill of worker” is built into these machines, making
it possible for inexperienced operators to reproduce identical parts.
In contrast, the engine lathe requires a skilled operator and requires
more time to produce parts that are dimensionally the same. The
principal characteristic of turret lathes is that the tools for
consecutive operations are set up for use in the proper sequence.
Although skill is required to set and adjust the tools properly, once
they are correct, less skill is required to operate the turret lathe.
Many parts can be produced before adjustments are necessary.
• Horizontal turret lathes, shown in Fig. 3-10, is used for chucking
work, and the turret is mounted directly on a saddle that moves
toward the headstock by hand or power to feed the tools to the
workpiece, and withdraws to index the turret.
2.4.4 CNC turning centers
• Turret lathes have evolved into computer numerical controlled
(CNC) turning centers. These machines contain X, Y, Z, and C
axis control, so turning and milling can be done on the same
machine. The turret can hold 8 to 10 tools, with many of them
powered (having individual motors), as shown in Fig. 4-8 (a).
Some machines have automatic tool change (ATC) capability
with additional tools in a magazine. The C axis control
provides 360°location on the spindle, so the spindle can be
held in any orientation while the power tools operate. More
complex versions of these machines have two turrets and two
spindles, and parts can be automatically transferred from the
main spindle to the subspindle as shown in Fig. 4-8 (b).
Fig2-21 CNC turning center