Mini lathe machine project

BAHIR DAR UNIVERSTY
BAHIR DAR UNIVERSITY INSTITUTE OF TECHNOLOGY
FACULTYOF MECHANICAL AND INDUSTRIAL ENGINEERING
MECHANICAL ENGINEERING PROGRAM
STREAM MANUFACTURING
FINAL YEAR PROJECT TITLE:
DESIGN AND MANUFACTURING OF MOTOR DRIVEN LOW COST WOOD
LATHE MACHINE TO IMPROVE WOOD WORKING METHOD
GROUP MEMBER ID
1. NIBRET GETU …………………………060453
2. YEGNANESH ASHAGRE……………..060485
3. TEMESGEN ANDUALM………………060471

Acknowledgement
Our deepest gratitude to Bahir Dar Institute of Technology to give this chance to elaborate our
theoretical knowledge to develop practical activities.
Thank to our advisor mr fetene who gives time to guide us and share his knowledge to do this
project in good manner.
Finally we would like to thank our beloved friends who give the comment on our project.

ABSTRACT
To achieve the aim of producing a functional and low cost wood lathe machine. We analyzed
and as well synthesized the different possible design solutions and concepts. We carried out the
analysis of different component part of the machine to determine their suitable dimensions based
on loading and stresses due to them. We used available local material and tool from a faculty
store workshop. We also made use of some machine tools in the school workshop. Finally, the
parts were assemble and the machine test – run. To ensure the achievement of best performance,
interactive procedures, were carried out. To achieve this preliminary experiment was carried out
to determine the optimum speed of this machine various design alternatives for achieving the
design solution were synthesized and a choice of an economic method which would satisfy the
objective was made. Based on the principles guiding the performance of the machine, the
dimensions and sizes of the various components were established. Appropriate materials were
subsequently selected and fabricated to required sizes. The machine was then assembled and
tested. After testing, it was found to perform efficiently thus satisfying the objective for which it
was designed. The material, labour and overhead costs were determined to get the production
cost of a prototype

Contents
Acknowledgement .......................................................................................................................... 2
ABSTRACT.................................................................................................................................... 3
CHAPTER ONE............................................................................................................................. 7
1. INTRODUCTION ...................................................................................................................... 7
1.1 BACKGROUND ...................................................................................................................... 7
1.2. STATEMENT OF PROBLEM.............................................................................................. 10
1.3. OBJECTIVES........................................................................................................................ 10
1.3.1. MAIN OBJECTIVES ..................................................................................................... 10
1. 3.2. SPECIFIC OBJECTIVES.............................................................................................. 10
CHAPTER TWO .......................................................................................................................... 11
2.1. LITERATURE REVIEW ...................................................................................................... 11
2.2. TREND IN LATHE MACHINE FABRICATION ............................................................... 12
2.3. SIGNIFICANCE OF STUDY ............................................................................................... 13
2.4. SCOPE OF STUDY............................................................................................................... 13
2.5. METHODOLOGY ................................................................................................................ 14
CHAPTER THREE ...................................................................................................................... 15
3.1. Conceptual design.................................................................................................................. 15
3.1.1 Clarifying objectives........................................................................................................ 15
3.1.2. Establishing functional structure..................................................................................... 16
3.1.3 Generate alternatives........................................................................................................ 17
3.2. SELECTION OF MATERIAL.............................................................................................. 23
CHAPTER FOUR......................................................................................................................... 24
4.1 DESIGN.................................................................................................................................. 24

4.1.1. EMBODIMENT DESIGN.............................................................................................. 24
4.2. Design analysis ...................................................................................................................... 25
4.2.2. Design of v-belts and pulley ........................................................................................... 26
4.2.3. Design of motor shaft...................................................................................................... 30
4.2.4. Design of Output shaft.................................................................................................... 31
4.2.5. Design of bearing............................................................................................................ 33
4.2.6 Geometrical of frame:...................................................................................................... 35
.4.3.Manufacturing process........................................................................................................... 38
CHAPTER FIVE .......................................................................................................................... 40
5.1. CONCLUSION...................................................................................................................... 40
REFERENCES ............................................................................................................................. 41

TABLE 3.1 RELATIVE IMPORTANCE VALUE POWER SUPPLY .........................................................................................................19
TABLE 3.2 RELATIVE IMPORTANCE VALUE WORK MECHANISM ...................................................................................................19
TABLE 3.3 RANK ORDER .....................................................................................................................................................19
TABLE 3.4 GIVE EACH VALUE IN RANK ORDER .........................................................................................................................20
TABLE 3.5 POWER TRANSMISSION........................................................................................................................................21
TABLE 3.6 WORKING MECHANISM FOR SUPPORT.....................................................................................................................21
TABLE 4.1 DIMENSION OF STANDARD V-BELTS ACCORDING TO IS: 2494-1974 ............................................................................26
TABLE 4.2 BELT LENGTH.....................................................................................................................................................26
4.4 TABLE MANUFACTURING PROCESS..................................................................................................................................38
FIG 3.1 STRUCTURAL FUNCTION ..........................................................................................................................................16
FIG 3.2 GENERATE ALTERNATIVE TREE DIGRAM.......................................................................................................................17
FIGURE 4.1 OVER ALL SHAPE OF THE MACHINE........................................................................................................................24

CHAPTER ONE
1. INTRODUCTION
1.1 BACKGROUND
The wood lathe machine is introduced to lessen the human suffering and to improve economic
and technological standard, and for years now Ethiopia recognized that was economically and
technological poor and has been economically dependent on the western world for survival in
terms of technology. To dis-encourage this importation of technological equipment placed
enlarge on the importation of certain goods and this inspired our people to recognized indigenous
technology through our fore father used axe, cutlass and some other sharp tools for designing
woods. But, as time goes on, technologist introduced mini wood lathe machine, which comes in
various designs and models as technology improves. Thus, the importance of wood lathe cannot
be over emphasized. It is the acknowledgement of this fact that led to the design of mini wood
lathe machine, even though this project of design and fabrication of wood lathe machine is a
copied design, we tried to improve more on this machine so that it can design wood with little or
no stress, utilizing the available material in order to reduced cost for production purposes and
durability being of utmost important. For the mini wood lathe machine to function and perform
its operations, various important parts are integrated together. These essentials parts make up the
lathe machine and include the following Stand (or legs). Stand or legs is used in holding the lathe
machine and in elevating the lathe bed to a working height.
1) Bed. The bed of a lathe machine is the base on which all other parts of lathe are mounted. It is
massive and rigid single piece casting made to support other active parts of lathe. On left end of
the bed, headstock of lathe machine is located while on right side tailstock is located. The
carriage of the machine rests over the bed and slides on it. On the top of the bed there are two
sets of guide ways-inner ways and outer ways. The inner ways provide sliding surfaces for the
tailstock and the outer ways for the carriage. The guide ways of the lathe bed may be flat and
inverted V shape.

2) Headstock. The main function of headstock is to transmit power to the different parts of a
lathe. It comprises of the headstock casting to accommodate all the parts within it including gear
train arrangement. The main spindle is adjusted in it, which possesses live center to which the
work can be attached. It supports the work and revolves with the work, fitted into the main
spindle of the headstock. The cone pulley is also attached with this arrangement, which is used to
get various spindle speed through electric motor.
3) Spindle. It is a hollow horizontal axle with interior and exterior threads on the inboard by
which the woodworking pieces can be mounted on.
4) Tailstock. It is commonly used for the objective of primarily giving an outer bearing and
support the circular job being turned on centers. Tail stock can be easily set or adjusted for
alignment or non-alignment with respect to the spindle center and carries a center called dead
center for supporting one end of the work. Both live and dead centers have 60° conical points to
fit center holes in the circular job, the other end tapering to allow for good fitting into the
spindles. The dead center can be mounted in ball bearing so that it rotates with the job avoiding
friction of the job with dead center as it important to hold heavy jobs.
5) Carriage. Carriage is mounted on the outer guide ways of lathe bed and it can move in a
direction parallel to the spindle axis. It comprises of important parts such as apron, cross-slide,
saddle, compound rest, and tool post. The lower part of the carriage is termed the apron in which
there are gears to constitute apron mechanism for adjusting the direction of the feed using clutch
mechanism and the split half nut for automatic feed
6) Cross-slide. The cross-slide is basically mounted on the carriage, which generally travels at
right angles to the spindle axis. On the cross-slide, a saddle is mounted in which the compound
rest is adjusted which can rotate and fix to any desired angle. The compound rest slide is actuated
by a screw, which rotates in a nut fixed to the saddle.
7) Tool Post. The tool post is an important part of carriage, which fits in a tee-slot in the
compound rest and holds the tool holder in place by the tool post screw.

8) Tool Rest. Tool rest is a horizontal area in line with the spindle and the tailstock from which
hand tools are braced against and levered into the work pieces. The tool rest assembly has a base
which rides on the ways. In a similar manner as the tailstock, the tool rest clamps to the ways to
keep it in one place. The tool rest base has a means of holding a vertical shaft and enabling it to
be adjusted up and down. The tool rest itself is made up of the vertical shaft and a horizontal bar
(or some other resting edge). The tool rest must be moved often while turning almost any object

1.2. STATEMENT OF PROBLEM
The continuous guest to have the problems of man and his growing needs solved has led to the
establishment of factories and other industries, which necessitates an intermediate technology.
However, simple hand tools that were in used before are no longer efficient for mass production.
In the same manner the importation wood lathe machine as a substitute for these tools, likewise
has failed to meet man’s insatiable economy. Then, there comes the need for urgent attention to a
better and locally made wood lathe machine.
1.3. OBJECTIVES
1.3.1. MAIN OBJECTIVES
The main objective of the project is to design and manufacturing of motor driven mini wood
lathe machine to produce good quality wood products
1. 3.2. SPECIFIC OBJECTIVES
 To Select the high value conceptual design
 To Develop embodiment design
 To Design each components
 To Modeling and drafting each components
 Manufacturing all components
 Assemble
 To Testing prototype
 To estimate the resource requirement for designing mini wood machine.
 To schedule activities with required resources

CHAPTER TWO
2.1. LITERATURE REVIEW
Traditionally, it was thought that the ancient Egyptians introduced lather turning. Perhaps as
much as 4,000 years ago. Despite a lack of hard evidence, it was assumed that a civilized nation
as advanced as Egypt’s – is known to develop the Potter’s wheel and bow drill –possessed the
technical know – how and skill to have made the invention of the lathe inevitable. Instead,
scholars now believe that the lathe was invented around a thousand years B.C., and that its
development may have occurred simultaneously among the Etrusians in Italy, the Celts in Great
Britain, and the inhabitants of the Crimea. By the second century B.C., the lather was known to
most of the people of the Near East and Europe. Originally, the lather was vertically oriented,
like the Potter’s wheel. In the case of farning, the lather was eventually mounted on a table
France, to be used mainly in a standing position. Virtually all early lathes were powered by cord
and required that a helper assist the Craftsman and Non- metal (Hard wood). Those the frame
made of wood are faced with the problem of durability and the ability to withstand shock.
However, the major problems that are prevalent with the existing lathes are:
1. Retching and vibration which translates into the spindle and bindweed thereby making it
impossible to reduce anything accurately.
2. Base not rigid or heavy enough.
3. tai/stock base do not lock down well enough and operators often retightening it.
4. Tool rest do not lock down well enough.
Finally, as the furniture and founding industries demand for cylindrical object increases, the need
for effective, economical and efficient lathe arises. To meet up with the industrial demand and
combat the problems found in the existing wood lathe machines, hence the embarkment of this
project.

2.2. TREND IN LATHE MACHINE FABRICATION
The emergence of the lathe machine dated back to some thousand years B.C., but it gained
popularity between sixteenth and seventeenth centuries. Then opticians used it for cutting lenses,
used in the construction of astronomical Telescopes. They modified the relatively rough
technique for special purposes. Artisans and furniture makers used the large lathes in turning
fancy works, though the frames were made of wood and headstock depending on the work being
done.
Discussed below are some related lathe machines:
A) CENTRE LATHE MACHINE
The Centre lathe is used to machine metals, by rotating the work piece mounted between centers
against a cutting tool. The tool can be fed both transversely and longitudinally with respect to the
turning axis of the job. The tool can be operated manually of automatically and many shapes as
well as different works can be carried out on the Centre lathe such work as cylindrical, eccentric
or conical shapes can be machined. Also done on the Centre lathe are threading and boring
operations.
B) CERAMIC LATHE MACHINE
The ceramic lathe is used for ceramic machining alone, though the operation is similar to that of
the Centre lathe.
C) WOOD LATHE
The wood lathe, just like other types of lathe, can be used to carry out a wide range of machining
operations. It saves time and does not need much skill as in the use of hand tools.

2.3. SIGNIFICANCE OF STUDY
This project has much significance advantage for the society, for the company, for the furniture
manufacturers and for the academicians. This project mainly has two way advantages for
company one mass production of the machine and distribute to the customer for gain income.
Some of the advantages of the mini wood lathe machine are:
 To use available local materials in fabrication.
 To achieve a reduction in the cost of production of the machine.
 To reduce the labor cost and time spend on using hand tools for wood dressing.
 To create awareness for and encouragement of indigenous technology.
 Increase productivity and creativity.
 The Portable Mini Lathe is a simplest wood turning machine having simple
constructional parts which favors less effort to operate.
2.4. SCOPE OF STUDY
The scope of this project is starting from detailed study of the problem and finding out the
solution of the problem and reviewing the literature study which useful for the project and
collecting the available data to design each components of the machine with defined dimension
and make drafting with solid work software, manufacturing each components and assemble the
machine .finally test the prototype and check the achievement of objectives. Essentially, the
machine comprises the made of metal, with the headstock fixed in position, the tail stock moves
along the bed of the machine, and the tool rest hold by human. In operations, the machine is
limited to only scraping and cutting of any type of wood. Drilling operations cannot be
performed on this machine.

2.5. METHODOLOGY
Methodology that we follow to complete the study or project is highlighted as follows;
 Data collection will be done by literature survey, user study and market study through
questionnaires, videos and observation etc. about the existing wood lath machine.
 Identify the drawbacks or limitations of the existing wood lathe machine.
 Generate new ideas to solve these problems.
 Select the best idea to model the new mini wood lath machine.
 Prepare preliminary design or model of the modified sprayer depends on our idea using
solid work software. And material specification is done.
 Geometric and force analysis of each component is done based on the preliminary design
or model.
 Design the components.
 Preparation of manufacturing drawing or part and assembly drawing.
 Manufacture all components
 Assemble and testing
 Check prototype
 Finally conclude the study.

CHAPTER THREE
3.1. Conceptual design
3.1.1 Clarifying objectives
The objective of this project is to design the low cost wood lathe machine. It is described as
following work flow alternatives diagram
Figure 3.1 tree diagrams of work flow alternatives
low cost lathe machine
machine
power
diesel
electricicty
manual
petrol
transmision
belt
chain
gear
stund
fixed
movabele

3.1.2. Establishing functional structure
To establish the function required and the system boundary new design.
Energy Energy
Wood different shape furniture products
Fig 3.1 structural function
Low cost wood lathe
machine

3.1.3 Generate alternatives
To generate the complete range of alternatives design solution for the product and to widen the
search for potential for new solution.
Fig 3.2 generate alternative tree digram
Evaluating alternatives
Evaluating criteria
For power supply
A. cost
B. performance
C reliability
D availability
E maintainability
low cost wood
lathe machine
electrical
belt
fixed movable
chain gear
ptetrol diesal manual

For power transmission and working mechanism
 Noise
 Cost
 Performance
 Availability
 Maintainability
 Reliability
Weighting the evaluation criteria using decision matrix
The above-mentioned criteria for each level first should be computing each other to obtain their
relative value or the degree of affecting value.
Means of power supply. A .cost
B. performance
C. reliability
D. availability
E. maintainability
Total =10
Variant A B C D E RAW
TOTAL
RELATIVE
VALUE
A - 0 1 0 1 2 0.2
B 1 - 0 1 1 3 0.3
C 0 1 - 1 0 2 0.2
D 1 0 0 - 1 2 0.2
E 0 0 1 0 - 1 0.1

Table 3.1 relative importance value power supply
Means of power transmission and working mechanism
A. Noise
B. Cost
C. Performance
D. Availability
E. Maintainability
F. Reliability
Table 3.2 Relative importance value work mechanism
Variant A B C D E F RAW
TOTAL
RELATIVE
VALUE
A - 0 1 0 1 1 3 0.2
B 1 - 0 1 1 0 3 0.2
C 0 1 - 1 1 1 4 0.266
D 1 0 0 - 0 1 2 0.1333
E 0 0 0 1 - 0 1 0.0667
F 0 1 0 0 1 - 2 0.133
Total=15
Assign value
Rank order the list of objectives
The rank ordering processes is helped by systematically compering pairs of objectives one
against the other. A simple chart is used to record the comparison and to arrive the rank order.
Table 3.3 rank order
points Means
0 Inadequate
1 Low

2 Medium
3 High
4 Very high
Means of power supply
Table 3.4 Give each value in rank order
Variant cost performance Availability Maintainability Relativity
Diesel 3 4 2 2 3
Manual 4 1 4 2 1
Electrical 3 4 3 2 3
Petrol 2 3 2 2 3
Means of power transmission assigned rank value

Table 3.5 power transmission
Variant Noise Cost Performance Availability Maintainability Reliability
Belt 3 3 2 3 2 2
Chain 2 2 2 2 3 2
Gear 2 1 4 2 1 3
Table 3.6 working mechanism for support
Variant Noise Cost performance Availability Maintainability Reliability
Movable 3 3 2 2 1 2
Fixed 3 3 3 2 2 3
Determine the overall value
Multiplying each of the variant value with its respective value of the weighting function that
obtained.
For power supply
Electricity: (3*0.2) +(4*0.3) +(2*0.2) +(2*0.2) +(3*0.1) =3.2
Manual: (4*0.2) +(1*0.0.3) +(4*0.2) +(2*0.2) +(2*0.1) =2.3
Diesel: (3*0.2) +(4*0.3) +(3*0.2) +(2*0.2) +(2*0.1) =3.5
Petrol: 2*0.2+3*0.3+3*0.2+2*0.2+2*0.1=2.5
Total= 11
Relative importance value
Electricity =3.2/11=0.291
Manual=2.3/11=0.209
Diesel =3.5/11=0.31
Petrol =2.5/11=0.22
For means of power transmission

Belt: 3*0.2+ 3*0.3+3*0.1333+2*0.266+2*0.133=2.59
Chain: 2*0.2+2*0.3+2*0.266+2*0.133+2*0.133=2.06
Gear: 2*0.2+1*0.3+4*0.266+2*0.133+3*0.133=2.4
Total= 7.05
Belt: 2.59/7.05=0.367
Chain: 2.06/7.05=0.29
Gear: 2.4/7.05=0.34
For movable support
=3*0.2+ 3*0.3+2*0.266+2*0.133+2*0.0667+2*0.133=2.15
For fixed support
=3*0.2+3*0.3+3*0.2667+2*0.133+2*0.0667+3*0.133=2.68; Total= 4.87
For movable=2.15/4.87=0.44
For fixed=2.68/4.87=0.055
Comparing the relative value of alternative design
Each parameter scores are multiplied by its weighting value. The best alternative design is the
higher sum value.
For Power the electrical motor value is higher =0.31
For power transmission the belt relative importance value is higher =0.367
For fixed support=0.55

3.2. SELECTION OF MATERIAL
In the selection of suitable material to satisfy a particular design and product requirements, it is
necessary to look at many aspects to insure that the component or assembly can be manufactured
within the resources available that the completed product will function satisfactorily throughout
its design life and that all these can be achieved at an acceptable cost.
Parameter to be considered in the selection of materials are;-
1. Material properties
2. Manufacturing characteristics
3. Cost and availability
Table material list that can be used
No. Components material Mechanical properties
1 Shaft Cast iron 𝛔t=150Mpa, 𝛔c=570Mpa
𝛒=7200kg/m3
2 Bush aluminum 𝛔t=228Mpa, 𝛔y=150Mpa
𝛒=2680kg/m3
3 Casing Sheet metal
4 Tool post support Cold rolled steel 𝛔t=420Mpa, 𝛔y=350Mpa
𝛒=7870kg/m3
5 Pulley Aluminum 𝛔t=228Mpa, 𝛔y=150Mpa
𝛒=2680kg/m3
6 Belt Lather 𝛔t=20Mpa, 𝛒=7870kg/m3
7 Support /stand RHS

CHAPTER FOUR
4.1 DESIGN
4.1.1. EMBODIMENT DESIGN
Figure 4.1 over all shape of the machine
Dimensions and Specifications Below are the dimensions and specifications as regards the
fabrication of mini wood lathe machine.
1) Total length of the machine 1000mm
2) Total height of the machine600mm
3) Width of machine 500mm

4) The electric motor
5) RPM of motor 2820 rpm
6) Horse power capacity of the electric motor 3HP
7) Power of the electric motor 2.2kW
8) The space between the bed rails 100mm
9) Width of tailstock 200mm
10) Maximum length of work piece 500mm
11) Maximum diameter of work piece 100mm
4.2. Design analysis
Design Data;
Electric power 3 Hp /2.2kw and max input rpm 2820
The required output 1450rpm to 250 shape different structure
Velocity ratio (vr)
Turning moment (T)

4.2.2. Design of v-belts and pulley
The cross-sectional dimensions of V belts have been standardized by
manufacturers, with each section designated by a letter of the alphabet for sizes in
inch dimensions. Metric sizes are designated in numbers.
Though these have not been included here, the procedure for analyzing and
designing them is the same as presented here. Dimensions, minimum sheave
diameters, and the horsepower range for each of the lettered sections A, B, C, D
and E.
Table 4.1 dimension of standard v-belts according to IS: 2494-1974
Type of belt Power range
In Kw
Minimum
pitch
diameter of
pulley in
mm
Width
In mm
Thickness
In mm
Weight/meter
length in
newton
A 0.7-3.5 23 13 8 1.06
Table 4.2 belt length
Belt
section
Circumference, inch
A 26, 31, 33, 35, 38, 42, 46, 48, 51, 53, 55, 57, 60, 62, 64, 66, 68,
71, 75, 78, 80, 85,90, 96, 105, 112, 120, 128
Length Conversion Dimensions (Add the 1.3 quantity to the inside circumference to obtain the
pitch length in inches)
The groove angle of a sheave is made somewhat smaller than the belt-section angle. This causes
the belt to wedge itself into the groove, thus increasing friction. The exact value of this angle

depends on the belt section, the sheave diameter, and the angle of contact. If it is made too much
smaller than the belt, the force required to pull the belt out of the groove as the belt leaves the
pulley will be excessive
Face width of pulley i.e. diameter driver pulley (D1) = 23mm, and vr1=2, vr2=3, vr3=6, vr4=11
D2=2*23 =46mm
D3=3*23=69mm
D4 =6*23=138mm
D5=11*23=253mm
Face width (B) = [n-1] e+2f = (4-1) 19+2*13=83mm
Mass of pulley
Use aluminum density (ρ) = 7000kg/m3
Weight of pulley = 22.4N
The pitch length (LP) and the center-to-center distance (C) are: let assume C=300mm
, or 42inch
LP=1077mm or 42 inch then select from the standard v- belt type A42 Circumference, inch

Fig 4.2 free body diagram of belt transmission
Angle of lap on smaller pulley (θ) =180-2α=180-45=135°
=2.35rad
Groove angle (2β) from range of 31 to 38°
Mass of belt per length
Mass=area *length*density
Area=b*t-x*t=13*8-3.36*8=77mm2
Mass=77*1077*1000=8.3 kg
Calculate belt tension
Centrifugal tension (Tc)

Maximum tension of belt (T)
Let FS=4, ∂all=∂t/FS=20/4=5Mpa
Tight side tension (T1)
( )
( )
( )
Power transmitted per belt
Number of belt (n)

4.2.3. Design of motor shaft
Data:
Material Mild Steel, density =7400kg/m3,
Yielding stress (σy) =290Mpa, ultimate stress (σu) =480MPa, E=69GPa
Factor of safety : to make good allowance must be give appropriate factor of safety , on this
component applied load is static now it gives (FS) =3
Bending moment input shaft
W=total belt tension _ pulley weight (N/m)
Reaction force at A
Moment at A is equal to zero:
∑
Torque equivalent:
√ √
Diameter of input shaft in torque equivalent
W

√
Moment equivalent (Me)
( )
Select the large diameter value that is 22mm
Then Standard shaft step up by 3mm diameter, D=25mm
4.2.4. Design of Output shaft
Bending, torsion, and axial stresses may be present in both midrange and alternating
components. For analysis, it is simple enough to combine the different types of stresses into
alternating and midrange von Mises stresses .It is sometimes convenient to customize the
equations specifically for shaft applications. Axial loads are usually comparatively very small at
critical locations where bending and torsion dominate.
When the shaft is subjected to combined twisting moment and bending moment, then the shaft
must be designed on the basis of the two moments simultaneously. Various theories have been
suggested to account for the elastic failure of the materials when they are subjected to various
types of combined stresses. The following two theories are important from the subject point of
view:
1. Maximum shear stress theory or Guest's theory. It is used for ductile materials such as mild
steel
2. Maximum normal stress theory or Rankine’s theory. It is used for brittle materials such as cast
iron.

Let τ= Shear stress induced due to twisting moment, and σb = Bending stress (tensile or
compressive) induced due to bending moment.
According to maximum shear stress theory, the maximum shear stress in the shaft,
Fig 4.3 free body diagram output shaft
Bending moment diagram output shaft
W=total belt tension + pulley weight (N)
Reaction force:
RA+RB=W=1036.6…………………………………..1
Moment at A
∑
Then, RA =1036.6N-148N=852N
Moment at C is equal to zero:

∑
Torque equivalent:
√ √
Diameter of input shaft in torque equivalent
√
Moment equivalent (Me)
( )
Select the large diameter value that is 18 mm
Then Standard shaft step up by 10 mm diameter, D=30 mm
4.2.5. Design of bearing
Ball bearings provide better lubrication. They can resist heavier loads and higher speeds for
sufficient time without failure .Balls are made of high carbon steel. Ball bearings require less
space. As compared ball bearings are more costly, more sensitive to misalignment and dirt. Thus,
ball bearings are selected.
Advantages
 Low maintenance cost.

 Both radial and thrust loads can be carried.
 Lubrication is simple.
 Low wear.
 Heavier loads and higher speeds are permissible.
Disadvantages
 Sensitive to dirt and needs regular checking.
Fig 4.4 Selection of Ball Bearings
The dimensions of ball bearings can be selected on standard tables based on the diameter of
the output shaft they are going to be fitted. The diameter of the shaft is calculated to be 30
mm. Therefore, the bore diameter of the ball bearing will be 30mm. The following table
shows the selected values of the dimensions of the ball bearings from standard tables. There
are two bearings and the same for the two ends of the axle.
Bearing basic
number
Bore(mm) OD (mm) w (mm) R
fillet(mm)
sholder dia
(mm)Ds
Dh
406 30 90 23 1.52 63 80
405 25 80 21 1,3 55 70

4.2.6 Geometrical of frame:
To meet our objective and specifications select the standard like RHS 80*80*5
and hallow shaft outer diameter 60mm and inner diameter 54mm , construct bed,
tailstock and head stock structure. Make ergonomically safe and its preferable
4.2.7 Design for horizontal bar
The cross section of the bar is hallow square shape with the area 50mmx50mm*5 and length
of 1200mm.
Assume the bar is simple supported beam and the load it carries is a uniformly distributed load.
So for simple supported beam the maximum bending moment that carries uniformly distributed
load is given by the formula :- the overall weight of the machine 255N
Where; M=bending moment
W=distributed load
Z=section modules
Now, to find the maximum bending stress maX=
But,

Therefore;
Now let us calculate the maximum material stress.
Where E=young’s modulus=210 MPa
R= radius of gyration
Y=distance from neutral surface
√
√
During simple bending maximum stress will occur at outer layer.
Therefor; Y=0.025M
Therefor; b> so the design is safe.
Fig 4.5 Horizontal Bar Cross
section

4.2.8 Design for column
The column or leg supports the entire machine’s weight. So it is subjected for compressive stress
and buckling. The selected material is alloy steel with the following material properties.
Compressive stress
Young’s modulus; E = 210MPa
The given properties are: - for one column Axial load; P=255N
Factor of safety; f.s=2
Length of column; L=600mm
Fig4.6 Column frame
Now, from the Euler’s formula critical load (Pcr);
But,
But, let us take a square cross section column.
P=255N
P=255N

Now, we can calculate the stress induced ( in the column.
Since; it is safe.
To cheek the buckling effect we consider the deformation of column in length.
Deformation,
This is negligible in length. Therefore the column is safe.
.4.3.Manufacturing process
4.4 Table manufacturing process
Lathe machine Drilling machine Grinding and cutting
machine
Shaft  Cutting
 Turning
 facing
Pulley  Turning
 Facing
 boring

Sheet metal
working
 drilling  cutting and
welding
Leg support
and frame
 drilling  cutting and
welding

CHAPTER FIVE
5.1. CONCLUSION
In this project a study has been done on mini lathe machine to know about its
portability, reliability and cost reduction. A basic design of mini lathe machine has
been made and analysis has been done of the tool to determine the cause of failure
of the tool. The fabricated model of the design will be portable, cost efficient and
can be assembled and dismantle according to the use which will increase the
mobility of the machine and can be easily carried. The ordinary workers who can
at afford the conventional lathe machine can buy this portable mini lathe machine
and can perform their machining operation effectively. The mini lathe machine can
reduce the capital cost of machining reducing the labor cost. The machine would
be easy to handle because of its mobility and portability and can easily be
maintained. Because of its portability and small in size it will consume less power
than conventional lathes and at the same time will be simple and compact
performing machining operations.

REFERENCES
[1] Wood lathe with sliding, horizontally-rotatable headstock and variable speed drive, BAREY
D. WIXEY, 2015, “Description”
[2] Engineering design George E. Dieter and Linda C. Schmidt, fourth edition <conceptual
design>
[3] Wood Lathe, Raymond L. Wilson, 2013 “Description”
[4] Wood Lathe tool holder, LARRIE A. Tennant, 2014 “Abstract”
[5] William CALLISTER, Material Science and Engineering
[6] Design and Fabrication of Wood Lathe Machine,
https://www.grossarchive.com/upload/1426689913.htm
[7] Text book of machine design by R.S.KHURMI and J.K. GUPTA.2005, 5th
edition. “Design
analysis”
[8] SHIGLEY’S mechanical engineering design 9th
edition. “Design analysis”

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