Machining processes such as turning are used to further refine parts by removing unwanted material. Turning involves securing a workpiece to a lathe and rotating it at high speeds while a single-point cutting tool removes material. Common turning operations include external operations like turning, grooving, and threading as well as internal operations like drilling, boring, and tapping. Turning can achieve high tolerances and is well-suited for producing cylindrical or rotational parts.

1. Material Removal
Processes
EMC 2033 -LO#3(C)
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2. Machining processes and tools
 Parts manufactured by casting, forming, and other
shaping processes described before, often require
further operations before the product is considered
ready to use.
 the machining processes will add the necessary
features for the parts, such as shiny surfaces, threaded
sections, specific dimensional tolerances, and many
more.
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3. 3

4. Turning Operations
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5. Turning (lathe machining)
 Turning is a form of machining, a material removal process,
which is used to create rotational parts by cutting away
unwanted material.
 The turning process requires a turning machine or lathe,
work piece, fixture, and cutting tool.
 The work piece is a piece of pre-shaped material that is
secured to the fixture, which itself is attached to the turning
machine, and allowed to rotate at high speeds.
 The cutter is typically a single-point cutting tool that is also
secured in the machine, although some operations make
use of multi-point tools.
 The cutting tool feeds into the rotating work piece and cuts
away material in the form of small chips to create the
desired shape.
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6. Turning (lathe machining)
 Turning is used to produce rotational, typically axi-
symmetric parts that have many features, such as holes,
grooves, threads, tapers, various diameter steps, and even
contoured surfaces.
 Parts that are fabricated completely through turning often
include components that are used in limited quantities,
perhaps for prototypes, such as custom designed shafts
and fasteners.
 Turning is also commonly used as a secondary process to
add or refine features on parts that were manufactured
using a different process.
 Due to the high tolerances and surface finishes that turning
can offer, it is ideal for adding precision rotational features
to a part whose basic shape has already been formed.
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7. Turning Process Capabilities
 Turning is used for producing thin wall cylindrical or sold
cylindrical parts.
 It can be used with most types of materials, metals,
polymers, and some ceramics.
 It can achieve high precision tolerance of ± 0.001 in.
 Turning Advantages:
1. All engineering materials compatible and can be
fabricated by turning.
2. Very good tolerances can be obtained.
3. Short lead times compared to other processes.
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8. Turning Process Capabilities
 Turning disadvantages:
1. Limited to rotational parts (cylindrical shapes).
2. Part may require several operations and machines
3. High equipment cost.
4. Significant wear of tools and machine.
5. Large amount of scrap generated (chip waste).
6. Requires higher operator skills.
 Turning applications: can be used to manufacture
machine components, shafts, engine components.
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9. Turning Comparison to Casting
Parameter Turning Sand Casting
Advantages: All materials compatible,
Very good tolerances,
Short lead times.
Can produce very large
parts, Can form complex
shapes, Many material
options, Low tooling and
equipment cost, Scrap can
be recycled, Short lead time
possible.
Disadvantages: Limited to rotational parts,
Part may require several
operations and machines,
High equipment cost,
Significant tool wear,
Large amount of scrap
Poor material strength, High
porosity possible, Poor
surface finish and tolerance,
Secondary machining often
required, Low production
rate, High labor cost
Applications: Machine components, shafts,
engine components
Engine blocks and manifolds,
machine bases, gears, pulleys
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10. Turing Process Cycle
 Process cycle is the time required to produce a given
quantity of parts includes the initial setup time and the
cycle time for each part.
 setup time is composed of the time to setup the turning
machine, plan the tool movements (whether performed
manually or by machine), and install the fixture device into
the turning machine.
 The cycle time can be divided into the following four times:
1. Load/Unload Time.
2. Cut time.
3. Idle time.
4. Tool replacement time.
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11. The Turning cycle time:
1. Load/Unload time: The time required to load the
workpiece into the turning machine and secure it to the
fixture, as well as the time to unload the finished part.
2. Cut time The time required for the cutting tool to make all
the necessary cuts in the workpiece for each operation.
3. Idle time Also referred to as non-productive time, this is
the time required for any tasks that occur during the
process cycle that do not engage the workpiece and
therefore remove material.
4. Tool replacement time The time required to replace a
tool that has exceeded its lifetime and therefore become to
worn to cut effectively.
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12. Turning Operations:
 During the process cycle, a variety of operations may
be performed to the workpiece to yield the desired part
shape.
 These operations may be classified as external or
internal.
 External operations modify the outer diameter of the
workpiece, while internal operations modify the inner
diameter.
 The following operations are each defined by the type
of cutter used and the path of that cutter to remove
material from the workpiece
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13. 1- External Operations
 Turning :A single-point turning
tool moves axially, along the
side of the workpiece,
removing material to form
different features, including
steps, tapers, chamfers, and
contours.
 Facing: A single-point turning
tool moves radially, along the
end of the workpiece,
removing a thin layer of
material to provide a smooth
flat surface.
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14. 2- External Operations
 Grooving: A single-point
turning tool moves radially,
into the side of the
workpiece, cutting a groove
equal in width to the cutting
tool.
 Cut-off (parting) : Similar
to grooving, a single-point
cut-off tool moves radially,
into the side of the
workpiece, and continues
until the center or inner
diameter of the workpiece is
reached, thus parting or
cutting off a section of the
workpiece.
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15. 3- External Operations
 Thread cutting: A
single-point threading
tool, typically with a 60
degree pointed nose,
moves axially, along the
side of the workpiece,
cutting threads into the
outer surface. The
threads can be cut to a
specified length and
pitch and may require
multiple passes to be
formed
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16. 1- Internal Operations
 Drilling: A drill enters the workpiece
axially through the end and cuts a
hole with a diameter equal to that of
the tool.
 Boring: A boring tool enters the
workpiece axially and cuts along an
internal surface to form different
features, such as steps, tapers,
chamfers, and contours. The boring
tool is a single-point cutting tool,
which can be set to cut the desired
diameter by using an adjustable
boring head. Boring is commonly
performed after drilling a hole in
order to enlarge the diameter or
obtain more precise dimensions.
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17. 2- Internal Operations
 Reaming : A reamer enters the workpiece axially
through the end and enlarges an existing hole to the
diameter of the tool. Reaming removes a minimal
amount of material and is often performed after
drilling to obtain both a more accurate diameter and a
smoother internal finish.
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18. 3- Internal Operations
 Tapping: A tap enters the workpiece axially through
the end and cuts internal threads into an existing hole.
The existing hole is typically drilled by the required tap
drill size that will accommodate the desired tap.
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19. Taper turning
 The method used to turn a taper depends upon the
angle of taper, its length, and the number of work
pieces to be machined.
 Three methods are commonly used:
1).Form tool: Short tapers of any angle can be produces
by grinding the required angle on the cutting tool, the
cutting tool is then fed into the work until the desired
length of taper is produced.
 This method is normally used for short tapers such as
chamfers, both internal and external.
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20. Taper turning Methods:
 2).Top or compound slide method:
 This method is used for any angle, internal or external,
but the length is restricted by the amount of travel
available on the top slide.
 Taper turning is carried out by swiveling the top slide
half the included angle required on the work.
 Turning the angle is done by winding the top slide
handle by hand. The tool will feed at the angle to which
top slide is set. After the first cut, the tool is returned to
its starting position by rewinding the top slide, the feed
for the second cut is achieved
by moving the cross slide.
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21. Taper turning Methods
 This method is used for any angle, internal or external,
but the length is restricted by the amount of travel
available on the top slide.
 3) taper turning attachment:
 Taper turning attachments can be fitted at the rear of
the cross slide and can be used to turn included angles
up to 20℃ over a length of around 250 mm, both
internally and externally.
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22. 22

23. Cutting Tools and cutting Fluids:
 Knowing the operation and the machine, you can
select the type of cutting tool; knowing the work piece
material you can decide the cutting tool material,
cutting angles, the speed at which to run the work
piece or cutting tool and whether to use a cutting fluid.
 To Maintain the cutting tools in good condition,
knowledge of regrinding the tool usually by hand,(off
hand grinding)is required.
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24. Cutting tool materials
 Properties:
 The three essential properties which make the cutting
tool effective are
 1) Red hardness: The cutting tool must be harder
than the material being cut, otherwise it will not cut. It
is also required that the cutting tool remain
hard even when cutting at high temperature.
“ The ability of the cutting tool to retain its
hardness at high temperatures is known as
RED HARDNESS”
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25. Cutting tool Properties:
 Abrasion Resistance: When cutting the edge of the
cutting tool operates under intense pressure and will
wear due to abrasion by the material being cut.
Basically, the harder the material the better its
resistance to abrasion.
 Toughness: Extreme hardness unfortunately makes
the material brittle, this means that when cutting the
cutting on impact chips away(E.g. if the component
being machined has series of slots and the cut is
therefore intermittent.)
 To prevent the chipping of the cutting edge the cutting
tool must have certain amount of toughness. This
achieved only at the expense of hardness (More
toughness will reduce hardness)
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26. Cutting tools
 Stellite: it is cobalt chromium tungsten with no iron, it
can maintain its red hardness even at 700℃.
 Being casted hence, it is more expensive than HSS.
 Stellite tips are brazed to the tough steel shank.
 Cemented Carbide: these are produced by powder
metallurgy technique.
 They contain 70-90%(tungsten carbide- hard part)
and 10-30% ( cobalt – binding material).
 They are used for milling, turning, drilling and boring in
the form of tips brazed to shank.
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27. Types of cutting tool materials
 High speed steel (HSS)
 HSS consists of iron and carbon with different alloying
elements such as chromium, vanadium Tungsten and
cobalt.
 A general purpose HSS tool contain 18%Tungesten,
4% chromium and 1% vanadium and is referred to as
18-4-1 tool steel
 Lathe tool are made in two parts instead of one solid
part of expensive HSS.
 A cutting edge at the front is HSS and is butt welded to
the tough steel shank
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28. Cutting tools
 Diamond : it is the hardest known material. It is
expensive and difficult to shape.
 Synthetic or man-made material is now available with
its hardness approaching natural diamond.
 HSS are employed up to 1200m/min on non ferrous
materials and carbide tools can offer between 150-500
m/min depending upon the conditions.
 Synthetic diamond will outlast all other cutting tool
materials under the same conditions.
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29. Cutting tool angles
 All cutting tools whether held by hand or in the
machine, must possess certain angles in order to cut
efficiently. The first essential is the clearance angle,
which is the angle between cutting edge and the
surface of the material being cut.
 This clearance prevents any part of the cutting tool
other than cutting edge and the surface of the material
being cut, and eliminate rubbing.
 If more clearance angle is given the edge weakens
seriously, therefore a primary and secondary clearance
angles are provided.
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30. 30

31. Tool Angles
 Rake Angle: This is the angle between tool face and a
line at right angles to the surface of the material being
cut.
 This angle varies with the type of material being cut.
 Some material slide more easily than others, while
some breakup in to pieces ( Brass for instance has a
tendency to break in to small pieces therefore
0° 𝑖𝑠 𝑢𝑠𝑒𝑑. )
 Aluminum on the other hand, has a tendency to stick to
the face of the tool and requires a steep rake angle,
usually in the region of 30°
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32. 32

33. Rake Angle
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34. Rake Angle
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35. Cutting Tool Angles:
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36. Tool angles
 For general purpose machining a positive rake angle is
given and for brittle type materials the rake angle is
negative( to provide maximum strength to the tips.)
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37. The Equipment (Lathe Machine)
 Turning machines, typically referred to as lathes, can
be found in a variety of sizes and designs.
 While most lathes are horizontal turning machines,
vertical machines are sometimes used, typically for
large diameter workpieces.
 Turning machines can also be classified by the type of
control that is offered.
 A manual lathe requires the operator to control the motion
of the cutting tool during the turning operation.
 Turning machines are also able to be computer
controlled, in which case they are referred to as a
computer numerical control (CNC) lathe.
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38. Cutting Fluids:
 In general, the use of cutting fluids can result in:
1) Less wear on cutting tool
2) The use of higher cutting speed
3) Improved surface finish
4) Reduced power consumption
5) Improved control of dimensional accuracy
 The ideal cutting fluid, in achieving the above,
should:
1)Not corrode the work or machine
2) Have low evaporation rate,
3)Be stable and not foam of fume,
4)Not injure or irritate the operator
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39. Types of cutting fluid
 Neat cutting oil: These oils are blend of mineral oil
together with additives for extreme pressure
application.
 Used where extreme cutting condition exists, such as
cutting tough steel, for low speed and feed or places
there is risk of water based cutting fluid mixing with
machine oil.
 The main advantage of this oil is its excellent
lubricating property and good rust control.
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40. Cutting Oil:
 Soluble Oil: It is a blend of mineral oil and water.
 The excellent cooling property of water is combined with the
lubricating property of the mineral oil. (Emulsifiable Oil)
 If It is diluted with a ratio of 1:20 ( 20 part water for 1 part of oil)the
emulsion is milky white and is used for general purpose cutting on
lathe and milling and shaping.
 In the ratio 1:60 the emulsion is used for grinding and it has a
translucent appearance.
 The advantage is, it has greater cooling capacity than neat cutting
oil, lower cost reduced smoke and elimination of fire hazard.
 Disadvantage includes poor rust control compared with neat
cutting oil and if not used for several days the emulsion can
separate from water, be affected by bacteria and become rancid.
 Other types of oils used are: Synthetic oil, semi synthetic oil
and vegetable oil.
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41. Large lathe machine
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42. The Lathe Machine components
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43. Lathe Machine components:
 Bed : is simply a large base that sits on the ground or a table and supports the other
components of the machine.
 Headstock assembly : The headstock assembly is the front section of the machine
that is attached to the bed. This assembly contains the motor and drive system which
powers the spindle. The spindle supports and rotates the workpiece, which is secured
in a workpiece holder or fixture, such as a chuck or collet.
 Tailstock assembly: The tailstock assembly is the rear section of the machine that is
attached to the bed. it is used to support the other end of the workpiece and allow it to
rotate, as it's driven by the spindle.
 Carriage: The carriage is a platform that slides alongside the workpiece, allowing the
cutting tool to cut away material as it moves. The carriage rests on tracks that lay on
the bed, called "ways", and is advanced by a lead screw powered by a motor or hand
wheel.
 Cross slide: The cross slide is attached to the top of the carriage and allows the tool
to move towards or away from the workpiece, changing the depth of cut. As with the
carriage, the cross slide is powered by a motor or hand wheel.
 Compound: The compound is attached on top of the cross slide and supports the
cutting tool. The cutting tool is secured in a tool post which is fixed to the compound.
The compound can rotate to alter the angle of the cutting tool relative to the
workpiece.
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44. Work Holding in lathe machine
 Three jaw self centering scroll chuck
 Four jaw independent Chuck
 Collect chuck
 Chuck keys
 Face plate
 Centers
 Steadies
 Mandrel
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45. Materials Machinability and Selection
 Machinability of material defined as the ease or
difficulty with which a metal can be machined.
 This will effect the cutting tool life, surface finish produced,
and power required for machining.
 The Machinability of a material is usually defined in terms
of four factors:
1. Surface finish and surface integrity of the machined parts.
2. Tool life.
3. Force and power required.
4. The level of difficulty in chip control.
 A good machinability indicates good surface finish integrity, a
long tool life, and low power requirement.
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46. Machinability and turning chip
 Machinability and chip control: many types of
chips produced as byproduct in machining
operations, some are long, thin, stringy, and curled
chips, which can interfere severely with the cutting
operation by becoming entrapped in the cutting zone.
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47. Material Structure and Machinability
 The machinability of a metal is affected by its
microstructure and will vary if the metal can be
modified greatly by operations such as annealing, and
stress relieving heat treatments.
 Chemical and physical modifications of steel for
example will improve its machinability.
 Example: to make steel machinability better, free-
machining steel modified in the following manner by:
1. The addition of sulfur, or sodium sulfite.
2. The addition of Lead.
3. Cold working, which modifies the ductility.
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48. Factors influencing Machining operations
 There are major independent variables in cutting
process:
1. Tool material and coatings.
2. Tool shape, surface finish, and sharpness.
3. Work piece material and condition.
4. Cutting speed, feed, and depth of cut.
5. Cutting fluids.
6. Characteristic of machine tool.
7. Work holding and fixing.
Other variables includes: type of produced chip, energy
dissipated during cutting and temperature rise, too wear
and failure.
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49. Turning Machining Design rules
 Rules related to the Workpiece:
 Select a material that minimizes overall cost. An
inexpensive workpiece may result in longer cut times and
more tool wear, increasing the total cost, example Hard
steel.
 Minimize the amount of turning that is required by pre-
cutting the workpiece close to the desired size and shape
(or close to dimension casting).
 Select the size of the workpiece such that a large enough
surface exists for the workpiece to be securely clamped.
Also, the clamped surface should allow clearance
between the tool and the fixture for any cuts.
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50. Turning Machining Design rules
 Rules related to design features:
 Minimize the number of setups that are required by
designing all features to be accessible from one setup (to
reduce process time).
 Design features, such as holes and threads, to require tools
of standard sizes.
 Minimize the number of tools that are required.
 Ensure that the depth of any feature is less than the tool
length and therefore will avoid the tool holder contacting the
workpiece.
 Lower requirements for tolerance and surface roughness, if
possible, in order to reduce costs
 Avoid undercuts (An undercut can be either a protrusion or
a depression (hole or pocket), which requires an additional
difficult machining.
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51. Watch videos
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Watch video: http://www.youtube.com/watch?v=H0AyVUfl8-k
Work holding: ttp://www.youtube.com/watch?v=Q7QUiCJJmew&feature=relmfu
Cutting tools: http://www.youtube.com/watch?v=J63dZsw7Ia4&feature=relmfu
Lathe controls: http://www.youtube.com/watch?v=9-YF79xGies&feature=relmfu
https://www.youtube.com/watch?v=Za0t2R
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