07 lathe

Bench lathe, 1911
Ancient India Bow lathe, Roman Era
Pole lathe, 1250
Foot wheel lathe,
Leonardo da Vinci 1480
Egypt, 300 BC
Great wheel lathe, 1680
Lathe circa, 1850
2
LATHE-INTRODUCTION

 It is one of the most common and versatile metal cutting technologies. The machine is called lathe.
 In turning, a workpiece is rotated about its axis (cutting movement) as single-point cutting tools are
fed into it (feed and cutting depth movements), shearing away unwanted material and creating the
desired part.
 Typical geometries: Axially-symmetrical contoured part such as cylinders, cones and tapered shafts,
spheres, threads, etc
 Typical operations: Facing, Contour turning, Chamfering, Parting (Cut-off), Grooving, Threading,
Drilling, Knurling,…
LATHE-INTRODUCTION
N
N Spindle speed (rpm)
Vc Cutting speed (m/min)
fn
ap
Feed per revolution (mm/rev)
Cutting depth (mm)
r Positioning angle
VIDEO

MACHINE TYPES
Conventional lathes

MACHINE TYPES
Conventional lathes
• Manual movement execution.
•Manual tool and part change.
•Same part holding device for different
parts.
 Machining time: Important
 Idle time: Important
 Set-up time: small
 Series: Unitary or up to 10 parts
 Precision: IT7 , Ra:1.6 µm.
1.Bench / Center / Engine Lathe

MACHINE TYPES
Conventional lathes
 Turning of heavy and voluminous parts in
diameter and/or length.
 Several tools can work at a time.
 Machining time: Important
 Idle time: Important
 Set-up time: Important (due to the weight of the parts)
 Series: Unitary or small
 Precision: IT7 , Ra:1.6 µm.
2.Vertical Lathe

MACHINE TYPES
Conventional lathes
• SEMIAUTOMATIC lathe.
• Automatic tool change.
• Several tools can work at a time.
• Typical workholding device: collets
• Machining time: Less than in a bench lathe.
• Idle time: Less than in a bench lathe.
• Set-up time: Important at the beginning (all the
tools need to be adjusted).
• Series: 25 parts or more.
• Precision: IT 8 , Ra:1.6 µm.
3.Turret lathe
 The distinguishing feature of this type of lathe is
that the tailstock of an engine lathe is replaced by a
hexagonal turret, on the face of which multiple tools
may be fitted and fed into the work in proper
sequence.
 Due to this arrangement, several different types
of operations can be done on a job without
re-setting of work or tools, and a number of
identical parts can be produced in the
minimum time.
hexagonal turret

MACHINE TYPES
Conventional lathes
3. Capstan and Turret lathes
 Capstan lathes generally deal with short or long rod type blanks held in collet, whereas
turret lathes mostly work on chucking type jobs held in the quick acting chucks
 In capstan lathe, the turret travels with limited stroke length within a saddle type guide
block, called auxiliary bed, which is clamped on the main bed as indicated in Fig. 2,
whereas in turret lathe, the heavy turret being mounted on the saddle which directly slides
with larger stroke length on the main bed as indicated in Fig. 2.
Fig.1 turret lathe. Fig.2 capstan lathe

MACHINE TYPES
Conventional lathes
• Automatic movements execution
using cams.
• Automatic part feed and change.
• Important toolholder cost
• Machining time: Less than in a bench lathe.
• Idle time: Almost zero.
• Set-up time: Important (long tools set-up)
• Series: 1000 parts or more
• Precision: IT 8 , Ra:1.6 µm.
4.Single Spindle Automatic Lathe
VIDEO

MACHINE TYPES
Conventional lathes
• Automatic movements execution.
• Automatic part feed and change.
• Important toolholder cost.
• Highly skilled workforce needed to set the
machine.
• 6 to 8 parts can be produced at a time.
• Machining time: Very low
• Idle time: Almost zero.
• Set-up time: Very Important (long tools set-up)
• Series: 10.000 parts or more
• Precision: IT 7/8 , Ra:1.6 µm.
5.Multi Spindle Automatic Lathe

MACHINE TYPES
Numerical Control Lathes (CNC)

MACHINE TYPES
• It is the evolution of an engine lathe being equipped with
a CNC control.
• They offer high stability, but slow tool indexing and
changing.
VIDEO
1.Flat bed lathe
Video: Flat bed lathe

MACHINE TYPES
2.Vertical lathe • It is used for large diameter heavy parts.
• A gantry design with a ram is the base of construction.
• Double ram offers a higher productivity.
• Long tool change time and component loading/unloading.
• Applications: railway wheels, gas/steam/wind turbines,
aero engines,…
VIDEO VIDEO

MACHINE TYPES
• Used when machining from both sides is required
(both spindles synchronize for part changing).
• Higher productivity It may halve the cycle time
compared to a single revolver machine:
• Tandem turning (same side turning).
• Machining operations on the sub-spindle at the same
time as the main spindle.
• Typically 3 turrets (2 for the main spindle and 1 for
the sub-spindle), but 2 turrets also exist.
• Typical applications: Long slender components like
shafts and components machined on both sides.
3.Turning centre
TWIN / DOUBLE / SUB SPINDLE
VIDEO VIDEO

MACHINE TYPES
• Spindle has the axial movement for workpiece load and
machining, not the tools.
• Nearly always fitted with a bar-feeder ( 0.5mm - 40
mm).
• Uses a headstock possible to machine long components
and small diameters without using a secondary spindle.
• Workpiece clamping system collet.
• Application: complex, precise and small size parts.
VIDEO VIDEO
4. Sliding head machine or Swiss type
lathe (I)

Video: Sliding head machine or Swiss type lathe

MACHINE TYPES
Sliding head machine or Swiss type lathe
VIDEO

MACHINE TYPES
• Several technologies are integrated into one
machine: turning, milling, drilling,…
• It has evolved from turning machines.
• The heart of the machine is the tool spindle (B
spindle), which even can be tilted. It provides
milling, drilling and tapping capability along with
turning, facing, grooving and threading.
• This spindle is serviced by an automatic tool
changer that resides outside the cutting zone.
• It may have a double spindle and one/two tool
turrets.
• Application: very complex parts.
5.MULTITASKING MACHINE – HORIZONTAL

MACHINE TYPES
MULTITASKING MACHINE – HORIZONTAL

Video: multitasking machine – horizontal

MACHINE TYPES
6.Single Spindle Automatic Lathe
VIDEO
24

MACHINE TYPES
7.Multiple Spindle Automatic Lathe
VIDEOVIDEO

Video: Multiple Spindle Automatic Lathe

WORK HOLDING DEVICES
1.Jaw chuck
Part clamped within a chuck and with no additional
support (maximum recommended cantilever 1.5 Diameter)
Posibility to hold cylindrical or poligonal parts
(side number equal or multiple to the number of
jaws).
Most common Chuck: Self-centering jaws
Movement controlled by a single screw operated by a “T”
shape key. The jaws move simultaneously and exactly
the same amount of movement toward center.
Cantilever L < 1.5Ø

Chucks: Manual
VIDEO
Chucks: Power driven
Pneumatic or Hydraulic Magnetic operated
Centering is more complex.
Working with small workpieces is
more difficult because they lack
sufficient surface area.
Independent jawsSelf-centering jaws
VIDEO
VIDEO

Chucks: Number of jaws
Six jaw chuckFour jaw chuckThree jaw chuckTwo jaw chuck Eight jaw chuck
Chucks: Ring and discs
Holding with
external part
Holding with
inverted jaws
Chucks: Soft jaws
• To hold cylindrical parts precisely as
well as irregular parts.
• Soft material jaws, without
being thermically treated. VIDEO

Video: Self-centering jaws Video: Independent jaws

2.Jaw Chuck and Center
• Part held on one side within a chuck and on the other
side with a live center.
• A lathe center holds the end of the workpiece,
providing support to preventing the workpiece from
deflecting during machining.
Live Center:
• Center contact point is mounted on bearings and allowed to
spin with workpiece. It is mounted in the tailstock quill (60º
vertex).
VIDEO

Between Centers
• Part hold within two centers (live center
and dead center).
• Rotation is produced thanks to a dog. It is
not an energetic holding but it offers an
excellent centering (finishing operations).
Dead Center:
• Solid steel tip that workpiece spins
against. It is mounted in the spindle hole
(60º vertex).

3.Face Plates
• It is used to grasp parts with irregular shapes.
• It is used when no other clamping system is valid.
• It is a custom-designed clamp for a particular geometry.

4.Steady and Follow rests
Steady rest
• Used in external or internal machining
operations.
• It stands stationary from a rigid mounti
• on the bed, and it supports the workpiece at
the rest's center, typically with three contact
points 120° apart.
ng
Follow rest
• External machining of parts mounted within a
chuck and center.
• It is similar to the steady rest, but it is mounted to
the carriage rather than the bed, which means
that as the tool bit moves, the follower rest
follows along.
VIDEO
VIDEOVIDEO

5.Mandrel
• For external/internal concentric machining operations.
• Mandrel: It is a hardened and ground cylindrical piece having undercut centerholes on both ends.
It is used for holding hollow workpieces, or those that have been drilled or bored previously.
Solid mandrel
• Mandrels have a slight taper (1:2000). The workpiece is
just fixed by friction. The ends of the mandrel have
machined flats for the lathe dog to grip.
• Since solid machine mandrels have a very slight taper, they
are limited to workpieces with specific inside diameters.
• The workpiece is mounted on a cylindrical shaft and is
axially fixed using nuts.
• The coaxiality between the inner and outer diameter of the
workpiece depends on the workpiece and mandrel
adjustment.
Gang mandrel

Cone mandrel
• The workpice is fixed by means of an elastic collet
(B). The collet is expanded by pressing the nut (D)
against the taper shaft (M).
• On the same mandrel different size elastic collets can
be mounted to fix different diameter workpieces.
Expansion mandrel
• It is a very effective device for holding a part that has a
hole drilled through it.
• The part is secured between the tapers of the mandrel.
VIDEO

6.Elastic collets
• Commonly used in turret lathes and automatic
lathes.
• Collet: Taper body with an axial hole where the
workpiece to be machined is introduced (cylindrical,
rectangular, hexagonal,… bars).
• Longitudinal cuts offer elasticity to the collet and a
uniform fixture is obtained.
The taper body is pulled manually or automatically against
the machine frame and the workpiece is fixed by pressure
(axial movement is needed to clamp/unclamp the
workpiece).
VIDEO

TOOLHOLDING DEVICES
Tool holding system
1.Tool post
BORING BAR
SHANK
SPRING CLAMP

TOOLHOLDING DEVICES
Shank turret
VDI turret
(Verein Deutscher
Ingenieure)
Designed for shank and cylindrical
holders. Driven solutions can not be used.
It has been the standard quick change
solution. Driven units can be adopted, although
the bearings are always outside the turret.
Tool holding system
2.Turret

TOOLHOLDING DEVICES
Coromant Capto Interface
(CBI) turret
VIDEO
Coromant Capto Disc
Interface (CDI) turret
Driven solutions can be
mounted inside or outside the
turret.
New solution to replace shank and VDI turrets
Driven tool holder (DTH) bearings mounted inside the turret.
Tool holding system
Turret
44

TOOLHOLDING DEVICES
Four turning tools in one Two turning tools in one
Tool holding system
Mini-turret

Lathe Specifications
1. Length between the centers
• It is the measure of the maximum
length of the workpiece
that can be fixed between the
lathe centers
2. Height of the centers
• It is the distance between the
lathe axis and the lathe bed

Lathe Specifications
3. Swing diameter over the bed
• It is the maximum diameter of the workpiece
that can be turned on a lathe without hitting
the lathe bed
4. Swing diameter over the carriage
• It is the maximum diameter of the workpiece that
can be turned on a lathe without hitting the
carriage
5. Maximum bar diameter
• It is the maximum diameter of the workpiece that can be
passed through the hole in the headstock

MACHINING OPERATIONS
1.Turning
Fr  = higher tool vibration.
Tool entry smoother.
Fr = radial
Fr =radial
Ff = axial
95°
Ff =axial
45°
• Turning is the operation of removing the excess material from the workpiece to produce a cylindrical
surface to the desired length.
External turning

2.Facing
VIDEO
VIDEO
• It is an operation of reducing the length of the workpiece by feeding the perpendicular to the lathe axis.
• This operation of reducing a flat surface on the end of the workpiece.
External turning

3.Chamfering
VIDEO
• It is the operation of getting a bevelled surface at the edge of a cylindrical workpiece. This operation is
done in case of bolt ends and shaft ends.
• Chamfering helps to avoid damage to the sharp edges and protect the operation getting hurt during
other operations.
External turning

4.Grooving
Outer Diameter (OD) grooving Face grooving
VIDEO
• It is the process of reducing the diameter of a workpiece over a very narrow surface. It is done by
groove tool. A grooving tool is similar to the parting-off tool. It is often done at the end of a thread
or adjacent to a shoulder to leave a small margin.
Two types of grooving:
External turning

Positioning
of the tool
Type of tool:
1.Insert type (shallow groove)
2.Screw-clamp (medium groove)
3.Spring-clamp (deep groove)
1
2
3
OD GROOVING:
VIDEO
1
Grooving
External turning

The correct curve on the tool is dependent on the radius of the workpiece.
FACE GROOVING:2
VIDEO
Left hand (L) tool
Right hand (R) tool
External turning

 Cutting tool has a shape that is imparted to the
workpiece by plunging the tool into the
workpiece.
 In form turning, cutting tool is complex and
expensive but feed is linear and does not require
special machine tools or devices.
 Cutting tool has a simple shape, but the feed motion is
complex; cutting tool is fed along a contour thus
creating a contoured shape on the workpiece.
 Not possible to be done efficiently in manual lathes.
5.Form turning
6.Profiling or Contour turning
VIDEO VIDEO
External turning

• This is not a machining operation but a plastic deformation
operation using a knurling tool.
• Criss-cross pattern knurls are the most typical (ocasionally
straight knurls are used too).
• OBJECTIVE: Knurling allows hands or fingers to get a better
grip.
VIDEO
7.Knurling
Knurling tool
Knurling wheels
or Knurls
Knurled part
• It is an operation of obtaining a diamond shape on the workpiece for the gripping
purpose.
External turning

8. Threading
• It is the important operation in the lathe to obtain the continuous ”helical grooves” or ” threads’‘.
• When the threads or helical grooves are formed on the out surface of the workpiece is called
external thread cutting. When the threads or helical grooves are formed on the inner surface of the
workpiece is called internal thread cutting.
External turning

 Spindle revolution (N) and feed per
revolution (fn) must keep a relation.
 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.
Insert types
Infeed strategies
8. Threading
Each insert can only
cut one pitch.
Can result in burr
formation that needs
to be taken away.
Reduced number of
infeeds
Productivity ↑
VIDEOVIDEOVIDEO
VIDEOVIDEO
External turning

1. Using a compound slide
2. Using form tools
3. Offsetting the tailstock
4. Using taper turning attachment
1. The compound rest may be swiveled on the cross-slide to any angle in the horizontal plane (short
tapers).
VIDEO
2. By offsetting the tailstock (Long and slim tapers, up to 10-15%).
9. Taper turning
External turning
Taper Turning Methods

1. Using a compound slide
• Limited movement of the compound slide.
• Feeding is by hand and is non-uniform.
• This is responsible for low productivity
and poor surface finish.
• Short and steep tapers can be easily
done.
Taper turning
D d
ℓ
θ
tan
2
D d
l


 ,
2 c
D d
Noof cuts n
d

 /
L
Time cut
f N


2. Using form tools
• Useful for short tapers, where the steepness is
of no consequence such as for chamfering.
• When turning long tapers with form tools, the
tool would likely to chatter (vibrate) resulting in
poor surface finish.
• However care of the form tools is a careful
exercise.
Taper turning
Video: form tools

3. Offsetting the tailstock
tan
2
D d
l



 
 
tan certain part length only tobe tapered
,
tan entirepart length tobe tapered
2
2 2
L
offset s
l
D d
L
l
D d D d
l
l



 



 
   

Taper turning
For tapers on longer shafts, you can offset the tailstock from the centre line.
The limitations are on the size of taper, it will only be
a shallow taper.
Calculations on the offset will be needed.
Video: Offsetting the tailstock

Taper turning
For longer tapers you can use a Taper Turning Attachment.
Video: taper turning attachment

• Long Tapers
• Power feed
• Taper angle limited to 6 – 7°
• Attachment
• Guide bar
• Sliding block
Taper turning
l
GL
x
2
d-D
setoverbarGuide 
For longer tapers you can use a Taper Turning Attachment.
 They attach to the lathe bed.
 Having set the angle on the attachment,
the cross slide is moved producing the
taper as the saddle moves along the bed.

 It consists on increasing a previously drilled workpiece diameter.
This operation is accomplished moving the tool using the
longitudinal carriage.
VIDEO VIDEO
1.Turning or boring
Internal turning

 It consists on machining internal surfaces perpendicular to the
part rotational axis.
 It is accomplished moving the tool along the transverse axis.
Tool movement using the cross-slide to allow thread exits, outlet for
the use of grinding wheels,…
2.Facing
3.Grooving
Internal turning

 It consists on machining internal surfaces perpendicular
to the part rotational axis.
 It is accomplished moving the tool along the transverse
axis.
4. Profiling
5.Taper turning
•The compound rest may be swiveled on the cross-
slide to any angle in the horizontal plane (short tapers).
• CNC lathes – 2 axes Interpolation
VIDEO
Internal turning

It consists on creating a blind hole or a through hole using a
drill. Two ways to obatain a gole:
1. The part spins and the drill has no rotation, only an axial
displacement thanks to the tailstock.
2. Using a live tool.
VIDEO
6. Drilling
WC HSS
Solid carbide drills Indexable insert drills Exchangeable tip drills
TIR(TotalIndicatorRunout)
0,02 mm 0,03 mm 0,02 mm
VIDEO
Internal turning

 It is a special drilling and
countersank (60º) operation done
with a center drill to fit later a live or
dead center.
7. Center hole machining
 The reaming is a finishing operation to achieve good
dimensional (H6,H7,H8) and surface tolerances depending
on the ream.
 Two ways to ream within the lathe:
 Keeping the part stationary and spinning the ream handle
manually (the handle is supported in the tailstock).
 Spinning the part (Mc) and moving the ream axially (Ma)
(held within a drill chuck).
VIDEO
8.Reaming
Internal turning

9.Threading
RIGHT SIDE LEFT SIDE
VIDEO
1
SINGLE POINT THREADING TOOL
Internal turning

LATHE MACHINE APPLICATIONS
AEROSPACE APPLICATIONS
4 – FAN CASTING –
Titanium
7 – COMBUSTION CASING –
Heat Resistant Super Alloy
6 – TURBINE DISC –
Heat Resistant Super Alloy

AUTOMOTIVE APPLICATIONS
GEAR WHEEL– Hardened Steel
SHAFT – Cast iron or steel

BIOMEDICALAPPLICATIONS
TULIP HEAD – Titanium
VIDEO
BONE SCREW –
Titanium or Stainless Steel
DENTAL SCREW –
TitaniumVIDEO

OIL & GAS APPLICATIONS
SPOOL BODY –
Steel or inconel
TUBING HANGER –
Steel or inconel
MANDREL – Steel

POWER GENERATION APPLICATIONS
STEAM TURBINE DIAPHRAGM
Stainless steel

POWER GENERATION APPLICATIONS
GAS TURBINE DISC
Inconel or steel
OPERATION OVERVIEW
1.Rough turning: outer diameter, facing
2.Pocketing
3.Grooving
4.Profiling
5.Finishing turning: O.D, I.D, faces
6.Drilling
7.Chamfering (front & back)

WIND POWER APPLICATIONS
GEARBOX SHAFT
Steel
MAIN SHAFT
Steel
OPERATION OVERVIEW
1.Turning – Heavy duty roughing
2.Turning – Semi roughing
3.Turning – Finishing
4.Drilling – Deep hole
5.Drilling – Short hole

07 lathe

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