Machining 2

Report
Machining 2
STSENGS855
MEM09002B-interpret technical drawing
MEM07005A-general machining
http://machineshop.coe.drexel.edu/mach
ineshop/equipment/milling-machines.jpg
Chapter 1
Determine job requirements:
Introduction
In order for parts of a product to fit together accurately, engineers need to
be able to understand engineering drawings so that they can make the
parts accurately.
http://kumasicenter.files.wordpress.com
/2012/10/engineering-drawings.jpg
In some cases, the parts to a product are not always manufactured in the
same country. Therefore it is important that Engineering drawings follow
the same format so that they can be understood all over the world.
Planning for Manufacture
In order to make any product an Engineer
will look at the engineering drawings for
the product and use the information on
these to plan the sequence of manufacture.
We need to plan the manufacture of a
product so that accidents and mistakes are
kept to a minimum.
http://upload.wikimedia.org/wikip
edia/commons/b/b2/Engineering_
drawings_with_Machinery%27s_H
andbook.jpg
Lots of time could be wasted if materials,
tools, equipment and staff are not available
at the time when they are needed.
1.1 Read and interpret mechanical
technical drawings.
When machining it
is good practice to
work from a
drawing of the part
or component.
Engineering drawing
are made up of
several elements and
features.
Part Drawing
Features
Elements
Elements of a part drawing
These are defined as ‘information aspects’ on the drawing.
Material: in this case the material to be used is cast iron,
however on some drawings you might come across the
following:
BMS – bright mild steel
Dimensions: these values inform the engineer of the overall size
of the finished part such as height, width and length.
Centre Line: this tells the engineer where to start a particular
machined feature.
Features of a part drawing
These are identified by the shape and appearance of the
designed part.
Edges: the drawing tells us that the location piece needs to have
two different machined slope features.
Hole: the drawing tells us that we need a 10 mm drill bit and that
we need to drill a hole depth of 40 mm.
Radius: The machine operator can plan ahead by making sure he
has all the tools ready for cutting this type of feature.
Leader and
arrowheads
Hidden edge line
12 mm in length at
an angle of 45
degrees
Centre line
Outside radius
measurement
Diameter of a hole
The unit of
measurement
used to produce
the drawing
What the part is
made from.
The name of the
creator
The company
details
Used for filing
purposes
Completed once
the part has
been machined
The date the
drawing was
done
The description
of the part being
machined
Student Tasks:
Read and interpret mechanical
technical drawings.
Have a go at reading the engineering drawing you have just reviewed previously.
The four key components have been extracted from the drawing to make easier
for you. Drag the correct description and place it on top of the target.
Unit
Company
info?
Date?
What
Material?
Centre line
Dia 10 mm
Hidden edge
Edge to
centre
Overall
length
Leader line
Centre line
Through
holes
Hidden edge
Highest
surface
Total depth
Nearest
surface
1.2 Determine and transfer
dimensions from given technical drawings
using datum points.
Machine operators are expected to
produce engineering parts to the
accuracy of the given drawing. Therefore
it is important that the information
regarding size and shape is clear and
easy to interpret.
Dimensions
It is not good practice to work from an
engineering drawing where no
conventions and standards have been
followed in relation to dimensioning.
Here we can easily note it is difficult to
determine which lines represent the
outline of the shape.
A well-drawn part should
follow the conventions
opposite. These linear
dimensions are vital to
the machine operator as
they will in most cases
prepare a slightly
oversized workpiece. This
will reduce the amount of
waste material after
machining the part.
When reading an
engineering drawing there
is likely to be different
methods used for
dimensions of a circle.
This will be determined by
the surrounding detail.
The steel flange opposite
illustrates the diameters
are identified. PCD pitch
centre line diameter
indicates the diameter of
the circle on which the
pitch of the holes is
centred. The pitch of the
circles is 60°.
Again, we can see that there are
also a number of methods used to
dimension arcs such as those that
distinguish the radii outline of an
irregular part.
Tolerances
Piston
Tolerance is the allowable variation in weight
or measurement of an object. It is important
for a machine operator to work to a tolerance
because it is not always possible to produce
parts exactly to the specified measurements.
The piston rings have to be machined to a
specific tolerance to prevent the engine from
losing power. If the diameter is greater then the
piston will be subject to high levels of friction
Piston in it’s cylinder
and visa versa.
of an engine
http://s1.hubimg.
com/u/623790_f5
20.jpg
Cylinder
Nominal Deviation of
Tolerances - Linear
Suppose a simple rectangular block has nominal
dimensions of 300 x 150 mm, but it is acceptable
for the manufactured item to be 1 mm over or 2
mm below the nominal size.
This can be shown in two ways on an engineering
drawing.
http://fr.norelem.de/en
/productsimages/0116
0.jpg
Rectangular block
The first method shows how much the
measurements can deviate from the
nominal dimension (between plus 1 mm
and minus 2 mm).
The second way of indicating these
tolerances is to specify the limits directly on
the component.
Nominal Deviation of
Tolerances - Angles
The diagram shows how tolerances
are indicated on an angular
measurement. The angle is nominally
35°, but the drawing indicates that it is
allowable for it to be up to 1° over or
2°under the nominal size
Surface finish
In some cases there
will be two different
surface textures on a
machine part.
Engineers need to be
made aware of which
the smooth and
surface textures
required. These need
to be measurable
and indicated on the
drawing.
The diagram shows
how surface texture
is indicated on
engineering
drawings. The value
has been stated in
micrometres
alongside the
symbol. A surface
texture of 3
micrometres is
required all over the
surfaces of the part.
Manufacturing detail
The machine operator needs to know a
number of factors before he/she can start
work such as:
• The material to be used.
• If a component of an assembly, then the
fitting method to be used.
• Any heat treatment.
This type of important detail is conveyed on
the drawing using symbols, written notes
which are placed near to the feature
Piston drawing 002
Geometrical tolerance
Although a part may be dimensionally accurate and within tolerance, the object’s
geometric features such as flatness, concentricity may need further definition.
This diagram shows the side view of a part whose perfect flatness is indicated by the
dashed line. However in reality the shape may be more like that shown by the solid
blue line. Therefore the uppermost line show that geometric tolerances have been
applied to specify how much variance is allowed.
Geometrical tolerance
This image shows how it would be shown
on a drawing.
Here a number of geometric
tolerancing symbols that are
likely to be on drawings.
Datum and Datum points
A
Datum is the origin from which the location or
geometric characteristic of features of a part is
established. It is represented by an axis, plane or exact
point. In a drawing it is symbolized by a letter in a
triangle.
In machining we refer to a feature as a physical
portion of a part such as a surface pin, hole or slot.
To machine these features, we have to exact points,
axes or planes which are known as datums.
A datum plane
Maximum Material
Condition (MMC) Largest pin diameter
Maximum Material Condition (MMC) refers to a
feature-of-size that contains the greatest amount of
material, yet remains within its tolerance zone. Some
examples of MMC include:
Smallest hole size
M
http://www.engineeringessentials.c
om/ege/tol/inch_tol.png
MMC is symbolized on a drawing by the letter ‘M’ in
a circle.
Least Material
Condition (LMC)
Smallest pin diameter
Least Material Condition (LMC) least material condition
(LMC) refers to a feature of size containing the least
amount of material, yet remains within its tolerance
zone:
Largest hole size
L
LMC is symbolized on a drawing by the letter ‘M’ in a
circle.
Regardless of feature size (RFS)
RFS is applicable
Regardless of Feature Size (RFS):
RFS is the default modifier. So if
there is no modifier symbol shown
in the feature control frame, it
means RFS is the default modifier.
RFS is used when the size feature
does not affect the specified
tolerance.
MMC and LMC’s symbols are modifiers in this case
Application
A
On an engineering drawing you may
find one of these three symbols
which are all used to identify a
datum.
On some cases there might be a
different letter used however letter
I, O and Q are not used.
A
A
Feature Control Frame
The Feature Control Frame is like a
basic sentence that can be read
from left to right.
It defines characteristic type,
geometric tolerance and value and
datum references.
http://docs.autodesk.com/ACD/2010/ENU/AutoCAD%202010%20User%
20Documentation/images/PTDCPM/Gator-All/English/auw0999u.png
The number of compartments in
the feature control frame can vary.
This is dependent on the
characteristic type used, whether
single or related and what the
functional requirements are.
Feature Control Frame
In the drawing we can see
the Feature Control Frame in
use. Datum references
indicated on the right end of
the feature control frame
which are read from left to
right.
The three letters signify
datum preference.
They establish the three
mutually perpendicular
planes.
http://dealertraining.cat.com/suppliertraining/Printreading/pr
mod3/images3/m31109.gif
Datum references
In the diagram opposite the
perpendicular planes (two
surfaces that are 90° to each
other) are the datum references.
The order of the datum
references starts with the first,
then secondary and finally
Tertiary planes
Part to be machined
http://images.books24x7.com/bookimages/id_17892/fig7
-1.jpg
Student tasks
Determine and transfer
dimensions from given technical drawings
using datum points.
Drag the
labels over the
correct
drawing
elements.
Projection
line
Dimension
Projection
line gap
Termination
(arrow head)
In line
arrowheads
Projection
line
extension
Complete the different methods of dimensioning the diameter of these circles.
Work out the tolerances as values based on the nominal measurements and visa
versa by matching them.
5001
91
+1
+1
4501
+1°
150
200
30
−2
−2
−2°
4998
88
4498
+1°
90
−2°
31
28
201
198
+1
4500
−2
+1
5000
−2
151
148
Match the geometric tolerancing symbols with the correct labels.
Flatness
Concentricity
Cylindricity
Straightness
Circularity
Focus on the
Feature Control
Frame to match
the symbols with
the correct
descriptors.
Primary
datum
Position
symbol
Tolerance
value
Diameter
symbol
Tertiary
datum
Secondary
datum
Chapter 2
Determine sequence of machining operations
Introduction
When it comes to machining parts, the
chances are that you will need to carry
out more than one operation.
Therefore it is important that you have thought
about how you are going to produce the
finished part to avoid any waste resulting from
an error.
http://www.
The most effective approach is to plan in the
form of a sequence of operations.
hsmworks.co
m/docs/cncb
ook/en/Proje
ct3_square_bl
ock_step_5back.png
Planning resources
Before a sequence of operation can be planned, the machine operator will
probably need to refer to a number of documents.
To machine affectively, we need to have:
A drawing – tells us what the component or part needs to look like.
http://www.lucastech
nical.com/wpcontent/uploads/LTSEngineering-DrawingExample.png
Planning resources
A job card – This document tells the operator what materials and resources are
needed and breaks down the machining processes into tasks.
http://jpkc.whut.edu.cn/ppkc/jxcadcam/include/editor/uploadf
ile/20130409212911365.gif
Planning resources
Data charts - reference material which informs the
operator on things such as machine speed, feed rate,
Limits and fits, threads, etc.
The above documents are generated in
different formats such as:
Hard copy
Soft copy
2.1 Plan a sequence of steps
for machining operations
This should include reference to the process,
materials and tooling.
Drawing
Before the
machining
operations can
be sequenced,
the operator
needs to
understand what
processes are
going to be
carried out.
Processes
1.
1
3
4
2
6
5
6 x threaded M4
holes.
2. 1 x 35 long x
3mm deep slot.
3. 4 radius corners.
4. A 3.5mm deep
step along all
four edges.
5. A 30 mm D blind
hole.
6. Material type
and size.
These are not in any
order
Machining processes
Preparing the stock so that the material is square is the first stage
of the operation.
Then the drilling of the 6 through holes would be
done next.
http://www.xstrange.
com/bridgemachining
450.jpg
The drilling and boring of the 30 mm diameter
blind hole would then be machined.
http://www.henkel
.de/de/content_im
ages/Multan_cutti
ng_fluid_278330_p
rint_1772H_1772
W.jpg
Machining processes continued
By using a slot drill in the milling machine we can machine out the
blind slot.
http://www.sandvik.coro
mant.com/SiteCollectionI
mages/Technical%20guid
e/Pablo/D%20milling/09
1689.jpg
http://grindaix.de/typo3temp/pics/11
4557b78c.jpg
The perimeter step is machined using an end
mill along with the radius corners with the aid
of a rotary table.
http://www.berryhillguns.com/mill.jpg
Materials
http://thumbs1.ebaystatic.com/d/l22
5/m/mwH_n1QLTs00hzEx25X3Ptw.jpg
Different
materials are
specified for
parts depending
on the function
of the part. Here
are some
common
materials that
are machined on
a lathe and
milling machine.
Aluminum
Brass
http://ecx.imagesamazon.com/image
s/I/71WAz7crclL.jpg
All three materials have
different surface hardness
properties.
This hardness is considered
when selecting cuttings tools ,
and setting the speed of
rotation.
Mild steel
http://img.directind
ustry.com/images_d
i/photo-m/castiron-rectangularblocks-78843782031.jpg
Data charts
The common materials that are machined on a mill have recommended cutting
speeds which cutting tool manufacturers design their products around.
Cutting speeds in metres per minute M/Min
Material
Cutting
speed in
metre/min
Aluminum
Brass
Mild steel
Cast iron
High
Carbon
steel
100
45
25
20
15
These speeds are based on cutting tools manufactured from high speed steel
(H.S.S) however the speed rates are different for carbide tipped tools.
By calculating the speed and feed rates for each cutter the machine operator is able to work out
how many parts they are likely to produce in given time frame.
By using a simple formulae we can calculate the spindle speed required for a number of cutting
tools and materials.
Example: to calculate the speed required to cut a
mild steel workpiece with a 8 mm diameter end
N = Number of revolutions per minute
mill the following needs to be done.
S = Cutting speed in meters/min
=3
D = Diameter of the cutter
  
N=

  
N=

  
N=

= 1041 Rev/Min
Feed rate
This is the rate at which the workpiece moves into the revolving cutter which is
expressed in millimeters per minute (mm/min).
Number of teeth
To calculate the cutting feed
we need to determine the
number of teeth on the cutting tool.
Cutting tool manufactures give
recommendations for cutting feed
stated as a value per tooth.
http://www.zps-fn.com/go_category_image.php?pid=166
Flutes
End mill
Slot drill
Drill bit
Vertical Cutter types
Boring cutter
Thread mill
The table below demonstrates this:
Feed per tooth in millimetres
Material
end mill
Slot drill
Face mill
Aluminum
0.40
0.06
0.2
Brass
0.30
0.05
0.2
Cast iron
0.30
0.05
0.1
Mild steel
0.20
0.05
0.1
High
carbon
steel
0.15
0.03
0.05
To calculate the feed rate in millimetres per minute (mm/rev) the following
equation is used:
f.t.p = Feed per tooth for a particular cutter and metal as given in the table.
N = Number of teeth on milling cutter.
Feed rate = f.p.t x N = mm/rev
Example: a 8 mm diameter end mill having 6 teeth is to be used for cutting mild
steel the following needs to be calculated.
mm/rev = 6 x 0.20 = 1.2
To calculate the table feed in millimetres per minute (mm/min) the following
equation is used:
Feed/rev = Revolutions per minute of the milling cutter.
f.t.p = Feed per tooth for a particular cutter and metal as given in the table.
Table feed (mm/min) = Feed/rev x N
Example: a 8 mm diameter end mill having 6 teeth is to be used for cutting mild
steel using the spindle speed 1041 (rev/min) the following needs to be done.
Table feed = 1041
x 0.20 = 208
Finally, the operator needs to calculate the cut time which is done using the
following formulae:
Cut length (mm) ÷ Feed rate (mm/min) = Cut time (min)
By referring to the original drawing at the start of this chapter we can see that the
length of the perimeter step is:
310 mm ÷
208 mm/min
= 2 min
Student tasks
Processses
Review the milling processes on this and the next slide, then label them with correct term below.
http://www.custom
partnet.com/glossar
yimages.php?iid=17
71
Face milling
http://www.customp
artnet.com/wu/image
s/milling/pocketmilling.png
End milling
http://www.custom
partnet.com/glossar
yimages.php?iid=17
37
Pocket milling
http://www.custompa
rtnet.com/glossaryima
ges.php?iid=1853
Boring
http://www.custompar
tnet.com/wu/images/
milling/boring-mill.png
Tapping
http://www.custompartnet.c
om/wu/images/milling/tappi
ng-mill.png
Drilling
Cutting tool Teeth and flutes
Planning sheet for plate
Name: Plate
Date: 18/03/14
Material: Mild steel 90 x 65 x 13 mm
Stag
e
Description
Tools needed
1
prepare the stock so that it is
square.
Hand file and
vice
2
Marking out of detail.
Marking out
dye, scriber,
centre punch,
hammer, square
Cutting
Speed
(rev/min)
Feed
Rate
(mm/min)
3
Drill the 6 through holes.
5 mm HSS drill
bit (2 flutes)
1562
0.10
4
A 30 mm Dia blind hole.
16 mm end mill
(2 flutes) then
30 mm boring
cutter (1 flute)
16 mm =
500
30 mm =
266
0.40
10 mm slot drill
806
0.10
5
1 x 3 mm deep slot.
Table
Feed
Rate
(mm/min)
Time
taken
(min)
78
1
40
1
0.20
Safety
precautions
With an
machin
first sta
prepare
so that
square
surfaces
Chapter 3
Select and mount tools:
• 3.1 Select appropriate tools for turning, facing
grooving and milling.
• 3.2 Show how to mount lathe tools and milling
cutters.
http://electron.mit.edu/~gste
ele/mirrors/www.nmis.org/Ed
ucationTraining/machineshop
/lathe/cuttools.gif
Select appropriate tools for turning and milling
3.1
http://www.efunda.com/
processes/machining/ima
ges/mill/end_mill_types_
1.gif
Introduction
Both the centre lathe and milling machines are universal in their
operation.
They can perform several different cutting task.
The type of task is determined by the feature requirements of the
component or part being manufactured.
The operator can then select or adapt existing cutting tools to suit.
Lathe cutting tools
http://www.youtube.com/watch?v=J63dZsw7Ia4
1.3 Machine Tool Basics -- Lathe Cutting Tools -- SMITHY GRANITE 3in-1
http://1.bp.blogspot.com/RSUTWNVS8tY/UJsLSf1sS4I/AAAAAAAAAXI/Yk
wz51urV6U/s640/single_pt_lathe_tools.gif
The profile of the cutting tool
determines the type of job it can do.
Selecting lathe tools
Lets consider the lathe machining operations of the thumbscrew
Step
Thread
Knurling
wheel
undercut
As we can see, there are a number required features. For purpose of
this job, the machinist is able to select an off-the shelf cutting tool for
each feature.
Facing
Features
Undercut
Tools
Step
http://www.micro-machineshop.com/lathe_tools_std_sha
pes.jpg
Knurling
wheel
http://collections.infoc
ollections.org/ukedu/c
ollect/ukedu/index/ass
oc/gtz103be/p05c.gif
The three types of lathe cutting tools
So that metal may be cut effectively and efficiently, the tool cutting edge must be sharp, have
enough support and be made from a suitable material. All lathe cutting tools must be hard
enough to maintain a cutting edge and tough enough to
withstand shock and heavy pressure.
Lathe cutting tool materials
1. H.S.S. butt welded onto a medium carbon steel
shank.
High speed steel (H.S.S.)
Shank
High speed steel is the most widely used cutting tool
material in machine shop
2. H.S.S. tool bits held in tool holders.
engineering. H.S.S. is used for lathe tools, drills, taps,
and reamers.
H.S.S lathe tools can be either of the two types:
Butt weld
Tool
holder
Tool bit
Tungsten carbide
This material is very much harder than high speed
Insert
steel, so higher cutting speeds are possible.
The two main types of tungsten carbide tools are:
1. The insert (tip) is brazed onto the shank. When
Braze
Shank
the insert is worn, it must be removed, the tip
turned and re-brazed back onto shank.
2. The tungsten carbide insert is clamped to the
Clamp
Insert
shank. When a cutting edge is worn the insert
can be turned around and accurately clamped in
position so that another cutting edge can be
used.
Sharpening lathe cutting tools
http://www.sherline.com/images/grndfg12.gif
Both high speed steel (HSS) and
Carbide tipped cutting tools when dull
need to be sharpened. This is done
using a grinding wheel on a bench
grinder.
http://4.bp.blogspot.com/tRFLbpVZkjI/TxScdnysElI/AAAAAAAAA38/dkYGJ
H2tks0/s1600/Bench+Grinder+Safety+Gauge++Back+%2528Rockford+Systems%2529.PNG
Cutting
tool tip
Grinding cutting tools is a skill and takes
some time to master. Bench grinders can
be very dangerous if operated by
untrained personnel therefore follow
safety guidelines.
Student task
Based on the tap wrench below, study the drawing and the
machining stages then match them up with the correct cutting
tool on the next slides.
84
100
Knurl
20
33.5
D9.5
2.5
30
12
5
Plan View (Body)
10
5
Plan View (H
Tap M8
C'Drill D8
D11
30
D4.5
5
At the other end, turn down a 45°
chamfer.
Drill a 9.5 mm hole all
the way through the
centre of the
http://www.da
workpiece.
7c.co.uk/techn
Cut a diamond knurl along a section
of the workpiece.
Cut two profile grooves at
the position shown on the
drawing.
ical_torque_ar
ticles/drill_bit_
2.jpg
Turn down a to a diameter
of 11 mm (check with
digital calipers).
Drill bit
Face-off both ends to a length of 100
mm (check with digital calipers).
Turn down a to a diameter
of 11 mm (check with
digital calipers).
Drill a 9.5 mm hole all
the way through the
centre of the
workpiece.
Cut a diamond knurl along a section
of the workpiece.
Cut two profile grooves at
the position shown on the
drawing.
Drill bit
At the other end, turn down a 45°
chamfer.
Face-off both ends to a length of 100
mm (check with digital calipers).
The milling cutting tool
http://www.youtube.com/watch?v=ckzK-LbeZmY
2.2 Machine Tool Basics -- Mill Cutting Tools -- SMITHY GRANITE 3-in-1
Again, the profile of a mill cutting tool
determines the type of job it can do.
http://electron.mit.edu/~
gsteele/mirrors/www.nmi
s.org/EducationTraining/
machineshop/mill/mcutte
rs.gif
Selecting
milling
tools
To manufacture the large jaw below there are a number of
milling operations which require different cutting tools.
Corner
rounding
Facing
Slot drills
Again, the features required can be machined using off-the-shelf
milling cutting tools.
Features
Facing
Slot drills
Slot drills
Corner
rounding
http://www.acutecsolutions.com/
wpcontent/uploads/2013/01/cornerrounding-cutter_no_bg.png
https://www.cromwell
.co.uk/images/product
/CTL/060/CTL0602353
D_0.jpg
http://imageserver.gra
inger.com/is/image/Gr
ainger/4RKH4_AS01?$
productdetail$
http://www.pwtools.com/ekmps/shops/pwtools/im
ages/20mm-hss-slot-drill-2-flutemilling-cutter-hsco-m42-cobalt20mm-plain-shank-x-110mm-o-lmade-in-uk-241p%5Bekm%5D433x324%5Bekm%5D
.jpg
http://www.harveytool.com/secure/C
ontent/Images/Thread%20Mill%20Ha
rvey%20Tool.JPG
http://ecx.imagesamazon.com/images/I/41
Im7fE1rBL._SL500_AA300
_.jpg
Student task
As with the large jaw, study the drawing of a pen holder and the
machining stages then match them up with the correct cutting
tool on the next slide.
Face-off the top surface of the
workpiece.
Drill out the three different size
holes.
http://www.engineeri
ngsupplies.co.uk/imag
es/my_images/metricthreadmill.jpg
Cut an internal M8
thread in the centre
hole.
http://www.maxt
oolsin.com/www
/media/products
/24.jpg
http://www.maxt
oolsin.com/www
/media/products
/24.jpg
http://www.chestermachin
etools.com/ekmps/shops/j
uliechuk/images/diameter-1-2-diameter-5675-p.jpg
Roll the workpiece forward so you can
face-off at right-angles to the top
surface.
cut all four edges to
create a set radius value
as stated on the
drawing.
http://www.maxt
oolsin.com/www
/media/products
/24.jpg
Face-off the top surface of the
workpiece.
Drill out the three different size
holes.
http://www.maxt
oolsin.com/www
/media/products
/24.jpg
cut all four edges to
create a set radius value
as stated on the
drawing.
Cut an internal M8
thread in the centre
hole.
http://www.chestermachin
etools.com/ekmps/shops/j
uliechuk/images/diameter-1-2-diameter-5675-p.jpg
http://www.engineeri
ngsupplies.co.uk/imag
es/my_images/metricthreadmill.jpg
Roll the workpiece forward so you can
face-off at right-angles to the top
surface.
http://www.maxt
oolsin.com/www
/media/products
/24.jpg
3.2
http://www.micro-machineshop.com/QCTP_14mm_crosslide_2.jpg
Show how to mount lathe tools and milling cutters.
Concentricity and eccentricity
When a component is being turned it
is usual for the operator to keep the
various diameters concentric.
They try to ensure that all the
diameters of a part or component
have a common axis.
The three diameters shown in the
left-hand drawing are concentric
(they lie on the same axis and have
the same centre of rotation.
Therefore the two diameters shown
in the right-hand drawing are
eccentric (they do not lie on the
same axis therefore have different
centres of rotation.
concentric
eccentric
http://abtechmfg.com/wp-content/uploads/location-toleranceconcentricity-2.gif
Introduction
In order to cut a workpiece accurately there are a number of factors that need to
be followed:
The position of the cutting tool in the toolpost.
Centre the cutting edge.
The safe setup of the cutting tool.
http://www.frets.com/Hom
eShopTech/Tooling/ToolHei
ghtSet/toolheightset.jpg
http://www.poolewood.c
o.uk/acatalog/474644.jpg
http://www.tacrockford.c
om/images/accessories/L
atheChuckShieldsHeader.
jpg
The position of the cutting tool
http://www.robotroom.com/DualF
an/ButtonTurning.jpg
In most turning applications the
cutting tool needs to be perpendicular
to the workpiece.
Screws
clamp
the tool
To avoid inaccurate cutting and
deflection, the cutting tool needs
to be secured tight in the toolpost.
http://www.youtube.com/w
atch?v=VkeW_Bcwj3E
Lathe Tool Post
Cutting
tool
There are a number of toolpost types
which are used to accommodate
different cutting tools. The most popular
one is the ‘quick-change’ toolposts as
Setting tool on centre height
To maintain the rake and clearance angles
on the lathe tool, it is important that the
tool is set to centre height. If the tool is
set above or below centre height, then
rake and clearance angles will change and
affect the cutting action.
The overhang of the cutting tool
should be kept to a minimum to avoid
vibration of the tool when cutting.
Methods of setting a tool on centre height
All tools that are to be used on a centre lathe must be set to the centre line of the machine, which is
called the centre height. Shims are used to set the tool to the correct height.
Shims
a) Using a live or dead centre
Shims
b) Using a setting gauge
Student task
Identify the parts of the quick-release toolpost by connecting the words to the features in
the picture.
Locking nut
Height
adjustment
screws
http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/Lathe_toolpost1.jpg
Tool block
Tool
Cutting tool
Mounting milling cutters
When it comes to mounting
milling cutters there are a
number of options depending on
the tool holding system that is
being used. However the
principles are similar apart from
the tools that are needed.
http://www.youtube.com/watch?v=r6MVhQtjN3I
The following video clip
demonstrates one of the most
common ways of mounting
milling cutters.
Student task
Identify the tools and parts of a vertical milling machine in relation to
mounting the
http://www.tormach.com/uploads/images/Gallery/pro
cutting tool by connecting the words to the features in the picture. ducts/order_by_partnumber/31911-Draw-Bar-forPower-Draw-Bar_MG_7382.jpg
http://www.toolmex.com/images/ecomm_images/Ite
ms/Large/3-185.jpg
http://www.tormach.com/uploads/images/Gallery/pro
ducts/order_by_partnumber/32336_Drawbar_Wrench
_MG_9345.jpg
http://img.directindustry.com/images_di/photog/morse-taper-shank-roughing-end-mills-851494155389.jpg
Milling
cutter
holder
Wrench/
hammer
Draw-bar
Milling
cutter
Chapter 4
Perform lathe machining operations
(Intermediate)
4.1 Select from a data table, an appropriate feedrate and speed
for a given workpiece and tool type.
4.2 Secure a workpiece in the lathe chuck and demonstrate lathe
machining operations for general turning, taper turning, grooving
and parting. Make sure that machining is performed in a safe
manner utilising all guards, safety procedures and personal
protective clothing and equipment.
The safe setup of the cutting tool
Whilst setup takes place, all guards need
to be engaged.
http://www.ferndalemachinery.com/img/repar/milling_m
achine_safety_guard.jpg
Machine
Guards
http://www.ferndalemachinery.com/img/repar/full-lathe-safetyguards.jpg

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