DESIGN PRACTICE OF JIGS, FIXTURES AND
PRESS TOOLS LAB - SPRX 4011
VII SEMESTER
2012-2016
MECHANICAL ENGINEERING DEPT
SATHYABAMA UNIVERSITY
DESIGN PRACTICE OF JIGS, FIXTURES AND
PRESS TOOLS LAB - SPRX 4011
VII-SEMESTER
MECHANICAL ENGINEERING DEPT
CONTENTS
 STUDY EXPERIMENTS
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Study of
Study of
Study of
Study of
jigs and fixtures
locating elements
clamping elements
press tools
 LIST OF DESIGN EXPERIMENTS FOR LAB
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Design of
Design of
Design of
Design of
Design of
Design of
channel jig for the given component
leaf jig for the given component
indexing jig for the given component
milling fixture for the given component
welding fixture for the given component
press tools for the given component
General theory about Jigs, Fixtures and Pressed Tools
Production Devices
Production devices are generally work holders with/without tool guiding/setting
arrangement. These are called jigs and fixtures.
 Jigs are provided with tool guiding elements such as drill bushes. These direct the
tool to the correct position on the work piece. Jigs are rarely clamped on the
machine table because it is necessary to move the jig on the table to align the
various bushings in the jig with the machine spindle.
 Fixtures hold the work piece securely in the correct position with respect to the
machine/cutter during operation. There is sometimes a provision of the fixture for
‘setting’ the tool with respect to the work piece/fixture, but the tool is not guided as
in a jig. Fixtures are often clamped to the machine table.
Elements of Jigs and Fixtures
 Locating Elements - These position the workpiece accurately with respect to the tool
guiding or setting elements in the fixture.
 Clamping Elements - These hold the workpiece securely in the located position
during operation.
 Tool guiding and Setting Elements – These guide or set of the tools in correct
position with respect to the workpiece. Drill bushings guide the drills accurately to
the workpiece. Milling fixtures use setting pieces for correct positioning of milling
cutters with respect to the workpiece.
Advantages of Jigs and Fixtures
 Productivity Jigs and fixtures eliminate individual marking, positioning and frequent
checking. This reduces operation time and increases productivity.
 Interchangeability Jigs and fixtures facilitate uniform quality in manufacture. There
is no need for selective assembly. Any parts of the machine fit properly in assembly,
and all similar components are interchangeable.
 Skill Reduction Jigs and fixtures simplify locating and clamping of the workpieces.
Tool guiding elements ensure correct positioning of the tools with respect to the
workpieces. There is no need for skillful setting of the work piece of tool. Any
average person can be trained to use jigs and fixtures the replacement of a skilled
workman with unskilled labor can effect substantial saving in labor cost.
 Cost Reduction Higher production, reduction in scrap, easy assembly and savings in
labor costs result in substantial reduction in the cost of workpieces produced with jigs
and fixtures.
Limits and Fits
The largest and the smallest dimension of the shaft (or hole) are called the high and low limit,
respectively. The difference between these limits, i.e. the permissible variation, is called tolerance. If tolerance is allowed only on one side of the nominal dimension it is called
unilateral. For example, 20.00+-00 has got unilateral tolerance. If tolerance is allowed on both
sides of the nominal dimension (e.g. 20.00+-01) it is called bilateral.
Classification of Fits
Tolerance and its direction depends upon the functional requirements of the assembled parts.
The following four classes of fits cover most of the functional requisites of engineering
assemblies.
 Running Fit This provides for easy rotation as well as axial movement of shaft (male
part) in hole (female part). It is used for bearing diameters of rotating shafts. Locators
in production devices are made running fit with workpiece for quick loading and
unloading.
 Push Fit This fit requires light hand pressure or tapping for assembly of the mating
parts. It is used mainly for precise assembly of replaceable locators in jigs and
fixtures.
 Press Fit The mating parts are assembled by hammering or with a press. There is a
positive interference between the hole and the shaft. This prevents rotary as well as
axial movement between the assembled parts. Hence, press fit is used widely for
assembly of drill bushings (outside diameter) and locators which are rarely replaced).
 Force Fit This is used for permanent assemblies such as wheels and hubs on shaft
force fit parts require heavy pressure for assembly. The clearance or interference
provided for obtaining the various fits is called allowance. In shaft basis of fits the
diameter of the shaft is kept constant while that of the hole is varied. In hole basis, the
hole size is kept constant and the shaft size is varied to obtain the various fits. As
most of the holes are made by fixed diameter tools (drills, reamers, etc.) the hole basis
is used widely in modem industry to keep the investment in cutting tools low.
 The International Standards Organization has standardized 27 types of fits and
18 grades of tolerances, which have been adopted by many countries. The
tolerance depends upon the mating diameter sizes.
High Precision
Hole/Shaft
Accurate
Hole/Shaft
1. Running Fit
2. Push Fit
H7//6
H7/H6
H8//7
H8/h7
3. Press Fit
H7/p6
H8/f>7
4. Force Fit
H7/ s6
H8/s7
Thus, by controlling the hole and shaft sizes within certain tolerances we can obtain the
desired fit with interchangeability in various assemblies.
Materials used in Jigs and Fixtures
Jigs and fixtures are made from a variety of materials, some of which can be hardened to
resist wear. It is sometimes necessary to use nonferrous metals like phospher bronze to
reduce wear of the mating parts, or nylons or fibre to prevent damage to the workpiece.
Given below are the materials often used in jigs, fixtures, press tools, collets, etc.
 High Speed Steels (HSS) These contain 18% (or 22%) tungsten for toughness and
cutting strength, 4-3% chromium for better hardenability and wear resistance and 1%
vandadium for retention of hardness at high temperature (red hardness) and impact
resistance. HSS can be air or oil hardened to RC 64-65 and are suitable for cutting
tools such as drills, reamers and cutters.
 Die Steels These are also called high carbon (1.5—2.3%) high chromium (12%)
(HCHC) cold working steels and are used for cutting press tools and thread forming
rolls. Hot die steels with lesser carbon (0.35%) and chromium (5%) but alloyed with
molybdenum (1%) and vanadium (0.3-1%) for retention of hardness at high
temperature are used for high temperature work like forging, casting and extrusion.
 Carbon Steels These contain 0.85-1.18% carbon and can be oil hardened to RC6263. These can be used for tools for cutting softer materials like woodwork,
agriculture, etc. and also for hand tools such as files, chisels and razors. The parts of
jigs and fixtures like bushings and locators, which are subjected to heavy wear can
also be made from carbon steels and hardened.
 Collet Steels (Spring Steels) These contain about 1% carbon and 0.5% Manganese.
Spring steels are usually tempered to RC 47 hardness.
Oil Hardening Non-Shrinking Tool Steels (OHNS)
These contain 0.9-1.1% carbon, 0.5-2% tungsten and 0.45-1% carbon, these are used for fine
parts such as taps, hand reamers, milling cutters, engraving tools, and intri- cate press tools
which cannot be ground after hardening (RC 62).
 Case Hardening Steels These can be carburised and case hardened to provide 0.6-1.5
thick, hard (RC 59-63) exte- rior. 17 MnlCr95 steel with 1% manganese and 0.95%
chromium is widely used. 15 Ni2CrlMol5 steel with addi- tional nickel (2%) reduces
thermal expansion up to 100°C. Case hardening steels are suitable for parts which
require only local hardness on small wearing surfaces where costlier, difficult to
machine full hardening tool steels are not warranted.
 High Tensile Steels These can be classified into medium carbon steels with 0.45%0.65% carbon (En8-9) and alloy steels like 40 Ni2CrlM028 (En24). The tensile
strength can be increased up to 125 kg/mm2 (RC 40) by tempering.
 Medium carbon steels are used widely for fasteners and structural work while alloy
steels are used for high stress applications like press rams.
 Mild Steel It is the cheapest and most widely used material in jigs and fixtures. It
contains less than 0.3% carbon. It is economical to make parts which are not
subjected to much wear and are not highly stressed from mild steel.
 Cast Iron It contains 2-2.5% carbon. As it can withstand vibrations well, it is used
widely in milling fixtures. Self- lubricating properties make cast iron suitable for
machine slides and guide-ways. The ingenious shaping of a casting and the pattern
can save a lot of machining time. Although, the strength of cast iron is only half the
strength of mild steel, a wide variety of grades have been developed. Nodular cast
iron is as strong as mild steel, while meehan- ite castings have heat resistant, wear
resistant, and corrosion resistant grades.
 Steel Castings These combine the strength of steel and shapabilty of a casting.
 Nylon and Fibre These are usually used as soft lining for clamps to prevent denting
or damage to the workpiece under high clamping force. Nylon or fibre pads are
screwed or stuck to mild steel clamps.
 Phospher Bronze It is widely used for replaceable nuts in screw operated feeding
and clamping systems. Generally screw making process is time consuming and
costly. So, their wear is minimized by using softer, shorter phospher bronze mating
nuts. These can be replaced periodically. Phospher bronze is also used in applications
calling for corrosion resistance, like boiler valves.
Constraints
Location should prevent linear and rotary motion of the workpiece along and around the
three major axes X,Y and Z.The plate shown in Figure 2.3 can move along the three axes X,Y
and Z and can also rotate around these axes. The location system should prevent all these
motions positively.
Motion Economy
Location system should facilitate easy and quick loading of the workpiece in the fixture. It
should effect motion economy. For example, there are two ways of drilling holes B and C in
the turned component We can drill either of the holes B and C first by locating on the
machined bore A and then, locate on the drilled hole to drill the other hole.
If we drill hole C first and use it for location we would have to use two locators at right
angles to each other and the workpiece need to be loaded on the locator for bore A first.
It would be necessary to use another removable locator for hole C. Otherwise it would not be
possible to load or unload the workpiece on the locator in bore A. Also, location on hole C
would involve two motions—first, loading on locator A then inserting a removable pin in
hole C which must be removed before the workpiece can be slid off axially from locator in
bore A for unloading.
On the other hand, if we drill hole B first and use it for location while drilling hole C, it is
possible to load the workpiece on both the locators in hole A and B in one motion as both the
locators would be parallel. Thus, parallel locators are preferable to those placed at right
angles.
Principles of Location
 Location must be related to the dimensional requirements stated on the
component/workpiece drawing.
 It is preferable to use a more accurately machined surface than a less accurate surface
for location.
 The workpiece should be prevented from moving along and rotating around the X,Y
and Z axes.
 Location system should facilitate easy and quick loading and unloading of the
workpiece and aim at motion economy.
 Redundant locators must be avoided.
 Location system should positively prevent wrong loading of the workpiece by fool
proofing.
Locating Methods
For Plane Surfaces
 A reasonably flat surface can be located by three pins of equal height having spherical
surfaces at the location points. A rough, uneven or tapered plane surface should be
located by three adjustable location pins having spherical ends.
 Additional adjustable supports are necessary to prevent vibrations or distortion of the
workpiece during machining operation. The force for adjusting the supports should be
kept minimum so that the workpiece does not get dislocated or lifted from the
location pins.
 A machined surface can be located by pads having flat surface.
 There should be ample clearance for burr or dirt to ensure proper seating of the
workpiece surfaces.
 A cube can be prevented from linear movement and rotation around axes X,Y and Z
by six location pads.
For Profile
 A profile can be located approximately by aligning it with a slightly bigger sighting
plate.
 Locating pins can also be used to locate a profile or cylindrical workpieces.
 Variations in workpiece sizes from batch to batch can be taken care of by using
eccentric locators whose eccentricity can be set to suit the batch.
 Workpieces with little variation can be located precisely with nesting plates with
suitable provision for unloading or ejection.
For Cylinder
 Spigots used for locating bores should have ample lead for easy entry and their
length should be short to prevent jamming of the workpiece.
 Long locators for fragile workpieces should be relieved at the centre.
 Location posts which are also used for clamping should be retained by a nut or a
grub screw.
 When two location pins are used, the less important one should be made diamondshaped. The important full pin should be longer than the diamond pin in order to
facilitate easy loading of the workpiece.
 Rough cored holes and bosses are located by conical locators which often have
integral clamping arrangement and drill bush.
 Fixed V blocks are used to locate approximately the outside surface of a cylinder.
 For precise location, an adjustable guided V block is necessary. The V block can
be adjusted by a screw or a cam. It can be withdrawn quickly by using a swinging
eyebolt.
 V blocks should be positioned in such a way that the variation in the workpiece
would not affect the location for the opera- tion. For drilling central holes, the
center line of V should be vertical.
Principles of Clamping
Clamping elements hold the workpiece firmly engaged with the locating elements during
operation. The clamping system should be strong enough to withstand forces developed
during operation. At the same time, the clamping force should not dent or damage the
workpiece. Speed of operation, operator fatigue and strategic positioning are other important
considerations for contriving a clamping system
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Position
Clamping should be positioned to direct the clamping force on a strong, supported part of
the workpiece. The clamping system should not obstruct the path of loading and
unloading of the workpiece. Clamps should not obstruct the path of the cutting tool. They
should not get drilled, milled or welded during operation.
 Strength
The clamping system should be capable of holding the workpiece security against the
forces developed during operation. The clamping force should not dent or damage the
workpiece with excessive pressure. For clamping weak or fragile workpieces, the
clamping force should be distributed over a wider area of the workpiece. While clamping
soft workpieces, clamps should be fitted with pads of softer materials, such as nylon or
fibre to prevent damage and denting of the workpiece.
 Productivity
Clamping time should be minimized by using hand knobs, tommy bars, knurled screws,
handwheels and handles (Figure 3.2), so that the clamp can be tightened or loosened
manually without using spanners, as a spanner further adds motions of picking, aligning,
and laying it down.
 Operator Fatigue
Operator fatigue should be taken into account. If a considerable number of clamps are to
be tightened and loosened repeatedly, it is better to use pneumatic or hydraulic clamping
which, in addition to reducing operator fatigue, also saves clamping time. Power
clamping facilitates tightening or loosening of many clamps simultaneously.
 Indexing devices
Indexing is a process of quick, accurate location of a workpiece or fixture in a number of
specific positions. Indexing involves periodic linear or rotary movement of the indexed
part to the next position. An indexing plunger locates the indexed part precisely in each
position. Linear Indexing :When a number of holes with the same size and pitch are to
be drilled in a workpiece, the cost of the jig can be reduced greatly by resorting to linear
indexing. Rotary Indexing Rotary indexing: facilitates accurate positioning of a part
around its axis. It can be used conveniently for drilling equi-spaced holes in round
workpieces.
Drill Jigs
The following are the requirements of a good drill jig
 Quick and accurate location of the workpiece.
 Easy loading and unloading of the workpiece and prevention of wrong
loading.
 Prevention of bending or movement of the workpiece during drilling.
 Ample chip clearance with facilities for metal filings removal and cleaning.
 Light weight to minimise operator fatigue, due to repeated handling.
 Prevention of loss of loose parts by chaining them to the jig body.
Drill Bushings
Drill jigs use bushings to guide drills, reamers and other cutting tools to the workpiece.
Bushings are made of water hardening carbon steel with 0.85-1% carbon and 0.5-0.9%
manganese, and is hardened to Rc 60-64 to minimise wear due to contact with hard, rotating
tools.

Press Fit Bushings
Press fit bushings are the most common type of bushings and are pressed interference fit
in the bushing plates also referred to as jig plates. These bushings are used in batch
production where the bushings often outlast the life of the jig.
 Renewable Bushings
For continuous or large batch production , the inside diameter of the bushing is subjected
to severe wear due to continuous contact with hard cutting tool. The guide bushings
require periodic replacement. The replacement is simplified by making the outside
diameter precision location fit (h6). The bushings can then be assembled manually
without any press. The use of liner in the jig plate provides hardened wear resistant
mating surface to the renewable bushing
 Slip Bushings
When a hole in the workpiece requires two operations such as drilling and reaming, it is
necessary to use two different guide bush' ings for the different tools. The hole is first
drilled using a bushing having a bore suitable for the drill. After drilling, the drill bushing
is removed and a reaming bushing is used to guide the reamer. In mass production, the
changeover of these bushings should be effected quickly. This is accomplished by
provision of slip bushings.
 Threaded Bushings
The bushings used for clamping the workpiece are threaded on the outside. There should
be another plain guiding diameter for accurate location of the bushing. The collar of the
liner bushing is usually placed on the opposite side to take the axial thrust of the screw.
The liner bushing should be prevented from rotation by a grub screw or a flat on the
collar.
Types of Jigs
 Plate jigs and channel jigs with workpiece pots
 Angle plate jigs
 Turn-over jigs
 Leaf or latch jigs
 Box jigs
 Trunnion-type indexing jigs
 Sandwich and pump jigs
Types of Fixtures
 Boring fixture
 Turning fixture
 Milling fixture
 Broaching fixture
 Grinding fixture
 Planning fixture
 Shaping fixture
 Welding fixture
PRESS TOOLS
Press machines and press tools are considered as a backbone of modern machine shop of large
industrial set up, producing wide variety of articles such as furniture, vehicle bodies, electrical
accessories, utensils etc.
PRESS WORKING TERMINOLOGY
 Bed The bed is the lower part of a press frame that serves as a table in which a bolster
plate is mounted.
 Bolster Plate This is a thick plate secured to the press bed, which is used for locating
and supporting the die assembly. It is usually 5 to 12.5 cm thick.
 Die set It is unit assembly which incorporates a lower and upper shoe, two or more
guide posts and guidepost bushings.
 Die The die may be defined as the female part of a complete tool for producing work
in a press. It is also referred to a complete consisting of a pair of mating members for
producing work in a press.
 Pitman It is a connecting rod which is used to transmit motion from the main drive
shaft to the press slide.
 Shut height It is the distance from top of the bed to the bottom of the slide, with its
stroke down and adjustment up.
 Stroke The stroke of a press is the distance of ram movement from its up position to
its down position. It is equal to twice the crankshaft throw or the eccentricity of the
eccentric drive. It is constant for the crankshaft and eccentric drives but it is variable
on the hydraulic press.
 Die Block It is a block or a plate which contains die cavity.
 Lower Shoe The lower shoe of a die set is generally mounted on the bolster plate of a
press. The die block is mounted on the lower shoe. Also, the guide posts are mounted
on it.
 Punch This is the male component of the die assembly, which is directly or indirectly
moved by and fastened to the press ram or slide.
 Upper Shoe This is the upper part of the die set which contains guide post bushings.
 Punch Plate The punch plate or punch retainer fits closely over the body of the punch
and holds it in proper relative position.
 Backup Plate Back up plate or pressure plate is placed so that the intensity of
pressure does not become excessive on punch holder. The plate distributes the
pressure over a wide area and the intensity of pressure on punch holder is reduced to
avoid crushing.
 Stripper It is a plate which is used to strip the metal strip from a cutting or noncutting punch or die. It may also guide the sheet.
 Knockout It is a mechanism, usually connected to and operated by the press ram, for
freeing a workpiece from a die.
ELEMENTS OF MECHANICAL PRESSES
 Capacity
 Press action
 Mechanism of slide operation
 Frame design
TYPES OF COMMON PRESSES
The names of commonly used presses are given as follows:
 Fly press
 Open back inclinable press (O.B.I)
 Straight side single crank press
 Eccentric or end wheel press
 Double action crank press
 One point press
 Two point press
 Double and triple action press
 Friction screw press
 Hydraulic press.
PRESS WORKING OPERATIONS
The operations are
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Blanking
Piercing
Bending
Swaging
Drawing
Planishing
Coining
 Embossing
TYPES OF DIES
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Blanking and piercing dies
Bending and forming dies
Drawing and deep drawing dies
Progressive dies
Compound dies
Combination dies
Special type dies
Exercise 1: Design and draw a channel jig for mild steel components as
shown in the figure to drill the hole of 18mm.
Component dimensions
SOLUTION
a. Selection of Bush
Generally the output diameter of the bush will be either push fit, press fit or transition fit.
The inner hole of the bush will be running fit.
select bush of fixed type DDB- 5.100
Bush
The diameter of the drill work piece id 18mm.
For 18mm diameter,
The tolerance for the inner diameter of bush is d1 f7Ø - running fit
Form DDB 3.9, d1= 18(+0.441,+0.020)
Note DDB - 3.9 tolerance is given in micron to convert it in to mm, multiply 0.001mm.
d2 = 30 mm
The tolerance for push fit d2h6 Ø
From DDB -3.7, d2 = 30(-0.000,-0.016) and other dimension of bush are
l1 = 20mm
l2 = 15mm
d3 = 35mm
b. Selection of locator (DDB-5.92)
The thickness of the jig plate must be equal to the distance (l2) of bush .
The jig plate thickness = 15 mm = l2 of the bush.
For better rigidity of channel jig , two locators and two clamp on each cam be used.
Select the locating pin corresponding to jig plate thickness.
Width of work piece (w) = 45
So the width of the jig is selected as 45 mm (same size),
For perfect alignment of two locators at a width of 45mm and
select locator head diameter as D=16mm, h1= 14mm
Locator
The other dimensions of locating pin are
d=15mm
h1 =14mm
h2 =22mm
d1 =12mm
d2 =11.5mm
The distance (h1) can be less than or equal to the thickness of jig plate.
c. Design of jig body (jig plate)
Width of the jig plate (W) = 45mm
Length of the jig plate = 2tp + Lw + h2 + Allowance
where tp - thickness of jig plate = 15mm
Lw - length of work piece = 75mm
h2 - Locator pin head length = 22mm
Allowance = 13mm
Length of jig plate = (2 × 15) + 75 + 22 + 13
= 140mm
Height of jig plate =Hw + tp + clearance for chip removal
where, Hw - height of work piece =52mm
tp - thickness of jip plate = 15mm
Note:
Clearance between work piece and top jig plate
1) For ductile material = ½ of the drill diameter
2) For brittle material = equal to diameter of drill
clearance = ½ × 18 = 9 mm
therefore Height of jig plate = 52+15+9 = 76mm
d. Selection of clamp (DDB - 5.104)
In order to clamp the right hand side of work piece , pressure pad with assembly can be
used.
Two clamp can be selected for better rigidity of jig. The pressure pad with be fixed at the
end of the clamp.
Clamp
The outer diameter of pressure pad
d₁ = 16mm and other dimension are
d₄ = 64mm
f = 3.5mm
d₅ = 12mm
h =9.5mm
d₆ = 7mm
d₇ =2mm
The size of screw with thread is M8
Assembly of channel jig and component
e. Bill of materials
S. NO.
1.
2.
3.
4.
PART NAME
Bush
Jig plate
Screw clamp with pressure pad
Locator
MATERIAL
Gun metal
Steel
Steel
Steel
NO
1
1
2
2
Exercise - 2: Design a leaf jig for drilling two holes of 10 mm diameter on
the given work piece.
Component dimensions
Solution
Design procedure
a. Selection of bush
Select the bush as fixed type [2 nos.]
DDB 5.100 for drill diameter = Ø 10mm.
Choose the bush diameter (d1) =Ø 10mm and the corresponding tolerance is d₁f₇ from DDB
3.9
Bush
d1 =10mm
L1 =20mm
d2 =18mm
L2 =16mm
d3 =22mm
d4 =16mm
for d2, tolerance is d2 h6 from DDB 3.7 For 18 mm
Therefore d2 = 18(-0.000,-0.013) mm (push fit)
b. Design of locator and supporting block
For cylindrical shape of work piece, from locator is fabricated.
V- block locator may be used . (The drawback is the height of the jig will be increased.)
Therefore, locator is selected.
From locator - 1No.
Locator
Supporting block
It is used to support the workpiece from bending during drilling operation. It is similar to the
hollow pipe as shown.
Supporting block
c. Design of clamp
In order to clamp the workpiece a pressure pad with assembly is used.(DDB 5.104)
Clamp
Let us the pressure psd maximum diameter as (d1) = 20mm to clamp the workpiece
perfectly . For d1 = 20mm, Take the other values from DDB as follows:
d4 =7.4mm
e =3.5mm
d5 =15mm
f =5mm
d6 =8mm
h = 12mm
d7 =2mm
r1 =2mm
r2 =0.4mm
Corresponding screw thread dimension is selected.
M10,
d. Design of jig plate
As we know thickness of jig = (L2) of bush
tp = 16mm
length of the jig plate = [ 2 × tp] + Lw + clearance on both side.
= [2 × 16] + [95] + [10+10]
L = 147mm (approximately 150mm)
where, tp = thickness of jig plate = 16mm
Lw = length of workpiece = 95mm
Height of the jig plate = tp + height of the locator + workpiece + clearance
= 16+10+42+20
= 88mm(approximately 90mm)
Width of the jig plate = Workpiece width + clearance on both side.
= 30+ [10+10] = 50mm
e. Design of leaf
Length of leaf = Length of leaf
= 150mm
Width of leaf = width of jig plate
= 50mm
Thick of leaf = Thick of jig plate
= 16mm
f. Selection of locking stud with nut
Leaf can be located by using a stud and an allen screw with a C - washer.
The dimension of above three can be taken from data book.
Let the dimension of the stud is 10mm, correspondingly other dimension are taken.
Assembly of Leaf jig and component
g. Bill of materials
S.No.
1
2
3
4
5
6
7
8
9
PART NAME
Clamping bolt
Bush
Leaf
Jig body
Supporting block
Screw
Component
Locator pin
Locator
MATERIAL
Mild steel
Brass
Mild steel
Cast iron (BC)
Mild steel
Mild steel
Mild steel
Mild steel
Mild steel
No. OFF
1
2
1
1
1
4
1
1
1
Exercise 3: Design an indexing jig for the flange coupling to drill 4 holes of
diameter 10mm on its pitch circle diameter.
Component dimensions
Solution
Design procedure
1. Design of indexing pin
The indexing pin is used to mark the 90 degree angle on the component of flank
coupling.
The diameter of the indexing pin down area is 10 mm with tolerances (+34,+16) and upper
area diameter is 20 mm. The length of both area are 50 mm and 25 mm respectively.
Indexing pin
d1=20mm
d2=10mm
L1=25mm
L2=50mm
2. Design of bush
Select the bush as fixed type.(DDB 5.100) for drill diameter =ɸ10mm
Choose the bush diameter (d1) = ɸ10mm and the corresponding tolerance of dIF7 from
(DDB 3.9)
Bush
d1 = 10mm
d2 = 18mm
d3 = 22mm
d4 = 16mm
L1 = 20mm
L2 = 16mm
For d2 tolerance is d2h1 from (DDB 3.7)
For 18mm
d2 = 18 (-0.000 , -0.013)mm (push fit)
3. Design of nut and bolt
The bolt and nut is used to hold the component and the jig body together and resist against
drilling force and do not allow the body to vibrate.
Selecting a hexagonal bolt
Bolt
S = 70mm
K = 30mm
t = 150mm
b = 50mm
m = 15mm
d = 30(+0.25 , +0.15)
The material used for bolt and nut is steel.
4. Jig body
The material used is steel. The jig body has two plate joined together in the form of ‘L’
shape.
Length of jig = 150mm
Thickness of jig plate = 25mm
Height of jig plate = 175mm
It has three holes
1) To fit bolt in middle
2) To fit bush
3) For indexing pin
Diameter of three holes are
D1 = 30mm
D2 = 18mm
D3 = 10mm
Assembly of Indexing jig and component
5. Bill of materials
S.NO.
1
2
3
4
5
6
Parts name
Jig plate
Component
Bush
Bolt
Index pin
Nut
Quantity
1
1
1
1
1
1
Problem 4: Design a milling fixture to cut a slot 3x3mm in 5 mild steel
cylinders.
Component dimensions
Solution
Given data
d = depth of cut = 3mm
b = width of cut = 3mm
Design procedure,
a. Selection of fixture,
b. Selection of locating method,
c. Selection of clamping method,
d. Design of fixture body.
a. Selection of locating fixture
To machine more than one number of similar workpieces string milling fixture is selected.
Number of jobs – 3 off.
Material – C45
Brittle hardness = 229HB
Surface finish = 0.025mm to 0.05mm
Type of milling used: Down milling
b. Selection of locating method
To accommodate workpiece of 40mm diameter, a V-block with dmax =40mm is selected
(DDB 5.97)
V-Block
From diagram, (corresponding to dmax)
A = 50; b – 40; dmax = 40; dmin = 5mm
c. Selection of clamping
To select the required clamping device, the clamping force should be calculated for which
the cutting force is required.
Cutting force Fc = 4.5 Kfdb/Cs in Newton
Assume, f = feed = 75mm/min
Material constant for high carbon steel (K)
K= 8.5 KN/mm^2 from table 3.2 [8.5KN/mm^2=8.5*10^3
N/mm^2]
Cutting speed Cs = 15m/min 15*10^3 mm/min.
Cutting force = 4.5Kfdb/Cs
= 4.5*8.5*75*3*3/15 Newton
For safer clamping force (fcp) must be greater than cutting force (Fc) (i.e) fcp>fc.
Here, yield stress( y) for work piece = 600N/mm^2 for C45 steel (DDB 1.12)
y= cutting force (fc)/Bearing area of pressure pad (a)
a= fc/ y= 1721.25/600 = 2.86mm^2
a = π/4*dp^2 = 2.86mm^2
Diameter of pressure pad (dp) =
/ = 2mm
Clamp
Since, dp = 2mm is not standard size as per standard data, select dp = 10mm which is the
minimum diameter of pressure pad available. (DDB 5.104)
From diagram;
d1 = 10; d4 = 3.8; d5 = 8; h=7; t1= 4.5mm
d. Design of fixture body
a. Design of base plate
Base plate
L2= number of work piece (c+dmax) + pressure pad height (h) + clearance for loading and
unloading of work piece
L1 = Height of v-block(c)
T = Diameter of work piece (dmax)
Thickness of supporting block (ts) = 1.5t
L = 2L1 + 2ts + L2
L = 2(L1 + ts) + L2
Height of supporting block should be height of v-block, which is less than height of work
piece.
hs = a = 50mm
Assume there are three work piece (n=5). Assume clearance =20mm
L2 = 5(40+40) + 7 + 20 =427mm =430mm(approx)
e. Calculation of width of the base plate and supporting plate
Base plate and supporting plate
Width of base plate (Wb) = 2times breadth of V-block
=2b = 2*40 = 80mm
Width of supporting block = Width of base plate
Ws = Wb =80mm
Assembly of Indexing jig and component
f. Bill of materials
S.No.
1
2
3
4
5
6
7
8
9
10
11
12
Parts Name
Base plate
Support block(a)
Support block(b)
Spindle
Holding block
Thrust plate
Stepped v-block
Standard v-block
Guide block
Work piece
Allen screw
Handle
Quantity
1
1
1
1
1
1
2
1
1
3
6
1
Material
C-40
C-40
C-40
M.S.
C-40
C-40
C-40
C-40
C-40
M.S.
M.S.
M.S.
Exercise 5: Design the welding fixture for to weld the plates of utt
configuration and the dimension given below.
Plate dimensions
Solution
Design procedure
1. Design of supporting plate
Supporting block helps for the supporting of the work piece and clamping of the work piece
during the wielding operation .
Supporting block is selected according to the material to be welded.
The length of the supporting block is slightly more than the length of the work piece.
A groove is provided at the middle of the supporting block of 10mm width and 5mm depth.
Groove is used so that the penetration of the weld material takes place completely to the
depth of the plate.
L =120mm
t =20mm
length of groove = 10mm
depth of groove =5mm
Supporting Plate
2. Design of clamp plate
The stop plate helps for the accurate alignment and settling of work piece at the fast rate and
automatic.
The accuracy of the alignment of the plate is very high and quick during the inner portion of
the stop plate.
The thickness of stop plate is equal to thickness of work piece.
t≥6mm ; length of stop plate = L
Clamp plate
3. Design of bolt
Bolt
Recommended practice for MIG welding of aluminium Alloy
Plate thickness = 6mm
Welding position = Horizontal , Vertical , Overhead , Flat.
Joint design = Single bevel, Double bevelled.
Current AC = 170-190, 180-240, 230-320A
AC voltage= 26-28 V
Filler wire diameter = 1.6mm
Argon gas flow =1.4 m^3/hr.
No. of passes = 2or 3
4. Bill of materials
S.No. NAME OF
COMPONENT
1
Supporting block
2
Clamp
3
Metal plate
TYPE OF
MATERIAL
Cast iron
Mild steel
Aluminium
NO.
1
4
2
4
Bolt
Mild steel
4
Exercise 6: Design a die for a 50 mm washer with 10mm hole in the centre.
Thickness of the washer is 0.8mm and material is mild steel.
The following procedure has to be adopted to the progressive die.
Data given:
Outside diameter of washer D=50mm
Inside diameter of the hole d=10mm
For piercing d=10mm
For blanking D=50mm
Design procedure:
1. Scrap/strip layout is drawn
2. Press-tonnage is calculated
3. Die dimensions like
a. Size of the die opening
b. Margin around the die opening
c. Thickness of the die
d. Overall length and width of die
4. Punch dimension like
a. Piercing punch size
b. Blanking punch size
c. Total height of the punch
d. Area of the punch block
5. Fastener are to be selected.
6. Based on the working area of the die block, suitable die set is selected.
7. Assembly is drawn.
1. scrap layout
For 50mm die web length (l) = 50*50 (DDB 13.9)
Margin ‘s’ for0.8mm thickness = 1.75mm
Width of the sheet (W) = 1+2(s) = 50+2(1.75) = 53.5mm
Scrap layout
For 50mm die web length (l) = 50*50 (DDB 13.9)
Margin ‘s’ for0.8mm thickness = 1.75mm
Width of the sheet (W) = 1+2(s) = 50+2(1.75) = 53.5mm
2. Selecting a progressive die in which piercing and blanking are done in two different
stations.
Press tonnage = Press tonnage in piercing + Press tonnage in blanking
Pt = Pp + Pb
In piercing operation
a. Inside diameter = d = 10mm
b. Thickness = t = 0.8mm
In blanking operation
a. outside diameter = (D) = 50mm
b. Thickness = (t) = 0.8mm
Ultimate shear stress of the mild steel (fs) = 120N/mm^2
Pt = Pp + Pb
Press tonnage = (π*d*t*fs) + (π*d*t*fs)
= (π*10*0.8*120) + (π*50*0.8*120)
= 18086.4Kg
= 20kN
3. Die design
Die opening for piercing = Basic size + clearance = d+ c [C = 0.05 for t= 0.8 (DDB
13.8)]
=10 + 0.05
=10.05mm
Die opening for blanking = Basic size = D
D = 50mm
Die thickness:
Blanking perimeter = 2πR (R=D/2)
= 2π *25
=157mm
From table, for plate thickness of 0.8mm (DDB 13.6)
a. Die thickness (td) = 0.4mm/(shear stress) (DDB 13.6)
b. As perimeter is greater than 50mm, the die plate thickness should be multiplied by the
factor 1.75 (DDB 13.7).
Die thickness = (td * fs ) * factor
Die thickness (td) = (4*12)*1.75 = 84mm
Since the die is mounted on die shoe, 50% of the above value may be taken.
Die thickness (td) = 42mm
Margin around die opening = 2* Die thickness (DDB 13.8)
= 2*42 = 84MM
For safety design die block area may be assumed 2 to 3 times die opening.
Area of the die block = 168 * 168mm^2
4. Punch design
Piercing punch size = Basic size = d
d =10mm
Blank punch size = Basic size – Clearance
C=0.05 for thickness t = 0.8mm (DDB 13.8)
= 50 – 0.05 = 49.95mm
Total height of punch = Die thickness (td) = 42mm
Area of the punch block = 168 * 168mm^2 = Area of the die blank
5. Fasteners
Based on the area of die block M12 screws 4 numbers are selected 12mm dwells 2
numbers are selected (DDB 13.6).
6. Die set selection
As 168*168 is not a standard size as per DATA. Select a 4 pillar die set with rectangular
working area of 355*255 mm^2 (DDB 13.5).
Progressive die set