Machine Drawing

MACHINE DRAWING

&

INDUSTRIAL DRAFTING

(MH402)

1

MACHINE DRAWING & INDUSTRIAL DRAFTING

Teaching Scheme (Hours/Week) Examination Scheme (Marks)

Lectures Tutorial Practical Theory Sessional Practical T.W. Total

--- --- 2+3 --- --- 50 50 100

PART A (MACHINE DRAWING) 1 PRINCIPLES OF DRAWING:

Drawing sheet (sizes and designations, title block, borders and frames, grid reference system), Scales (Designation, recommended scales, specifications), lines, lettering, sectioning, conventional representations, dimensioning, standard abbreviations

2 DETACHABLE FASTNERS:

Screw threads, approximate and conventional representations, specifications, Threaded fasteners (Types, forms, standard and specifications), Foundation bolts, locking devices (Classification, principles of operation, standard types and their proportions

3 PERMANENT FASTNERS:

Rivets (Standard forms and proportions), Riveted joints (Common types of joints, terminology, proportions and representations), Types of welds and welded joints, edge preparation, specifications and representation of welds on drawings, IS designation of weld symbols

4 ASSEMBLY DRAWING:

Review of sheet preparation, boundary lines, zones, title block, revision panel, parts list, numbering of components and associated detail drawing, bill of materials, assembly drawings of various machine sub-assemblies and assemblies from detail drawings, sketches and actual machine components

5 PRODUCTION DRAWING:

Limits, fits and tolerances of size and form, types and grade, use of tolerance tables and specification of tolerances, form and cumulative tolerances, tolerance dimensioning, general tolerances, surface quality symbols, terminology and representation on drawings, correlation of tolerances and surface quality with manufacturing techniques.

2


PART B (COMPUTER AIDED DRAFTING)

1 INTRODUCTION TO AutoCAD:

Starting with AutoCAD, AutoCAD dialog boxes, Co-ordinate Systems, drawing lines, circle, arcs, rectangle, ellipse, polygons, etc

2 EDITING SKETCHED OBJECTS:

Editing sketches, moving, copying, pasting, offsetting, scaling, chamfering, trimming, mirroring. Filleting, sketched objects

3 BASIC DIMENSIONING:

Geometric dimensioning and Tolerance: Dimensioning AutoCAD, Creating linear, rotated, angular aligned base line Dimensions, Modifying dimensions

4 PLOTTING:

Plotting the drawings in AutoCAD, plotting drawing using the plot dialog box, adding plotters and using plot styles, plotting sheets

5 BASIC 3D MODELLING

3


Text Books: Machine Drawing K. L. Narayana, P. Kannaiah, K. Venkata Reddy, 3rd edition, New age international (P) Ltd.

Machine Drawing N. Sidheswar, P. Kannaiah, V.V.S. Sastry, Tata McGraw Hill

Machine Drawing N. D. Junnarkar, Pearson Education Pvt. Ltd

Reference Books: P.S. Gill, Machine Drawing by S.K. Kataria, New Delhi

Sham Tickoo, AutoCAD 2012 CENGAGE learning Technical Drawing byGiesecke, F.E., Mitchel, A., Spencer, H.C., Hill, I.L.,, 13th Ed., Prentice-Hall SP 46: 1988 Engineering Drawing Practice for Schools and Colleges, Bureau of Indian standards 1988

PSG Design data book 4

Drawing sheet

Scales

Title block

Borders and Frames

Grid reference system (zoning)

Lines

Lettering

Sections

Conventional representation

Dimensioning

Standard Abbreviations

PRINCIPLES OF DRAWING

6

Use of standard size sheet saves paper and facilitates convenient storage of drawing

For sheet sizes the basic principles are; (a) (b) XY=1 For A0 size, surface area is 1m

2, X=841mm and Y=1189mm

Preferred drawing sheet sizes as per ISO-A series is given in Table 1.1

DRAWING SHEET

2:1Y:X

Table 1.1 7

The special elongated sizes are obtained by multiplying the shorter sides of the chosen basic format as shown in Table 1.2

DRAWING SHEET

Table 1.2

8

DRAWING SHEET

Figure 1.1 Drawing sheet formats

Different drawing sheet formats are shown in Figure 1.1

9

DRAWING SCALE

The proportion by which we either reduce

or increase the actual size of an object on

a drawing is known as drawing to scale or

simply Scale.

Scale is the ratio of linear dimension of an

element of an object as represented in the

drawing to the real linear dimension of the

same element of the object

Where ever possible, full scale is desirable

Enlarged scales are used for drawing very

small objects

Reduced scales are used for drawing very

large objects 10

DRAWING SCALE

SIZES OF THE SCALE

Full scale : 1:1

Reduced scales

The standard reducing proportions are;

1:2, 1:5, 1:10, 1:20, 1:50 and 1:100

Enlarged scales

The standard enlarging proportions are;

2:1, 5:1, 10:1, 20:1 and 50:1

11

DRAWING SCALE Complete designation of scale consists of

the word scale followed by the indication

of its ratio as:

SCALE 1:1 for full size

SCALE X:1 for enlarged size

SCALE 1:X for reduced size

Standard scales are shown in Table 1.2

Table 1.2 12

TITLE BLOCK

Important feature of the drawing

It gives all the information of the

prepared drawing

It is drawn at the bottom right corner

The recommended size of the title block

by Bureau of Indian Standards (B.I.S.)

SP-46:1998 is 185mm x 65mm for all

designations of drawing sheets

13

TITLE BLOCK

The title block should contain

- Title of the drawing

- Drawing/sheet number

- Scale

- Symbol, denoting the method of projection

- Name of the company/firm

14

TITLE BLOCK

15

DHARMSINH DESAI UNIVERSITY, NADIAD

FACULTY OF TECHNOLOGY

MECHANICAL ENGINEERING DEPARTMENT

NAME : CLASS : ROLL NO : START: COMP.: YEAR: 2011-12

DRAWING NO.: CHECKED BY:

TITLE OF THE DRAWING

50 50 150

15

15

50

BORDERS AND FRAMES

Border should be provided with all sheet

sizes

Borders have a minimum width of 20mm for

the sizes A0 and A1

Borders have a minimum width of 10mm for

the sizes A2, A3 and A4

A filling margin may be provided on far left

edge

16

BORDERS AND FRAMES

The drawing sheet layout is shown in Figure 1.3

Figure 1.3 17

CENTRING MARKS

Provided to facilitate positioning of the drawing when reproduced

Four centring marks may be provided

18

ORIENTATION MARKS

Provided to indicate the orientation of the drawing sheet on the board

19

METRIC REFERENCE GRADUATION

Provide figure-less metric reference Provided with minimum length 100mm and

divided into 10 intervals Drawn symmetrically about the centring mark

with width 5mm

20

TRIMMING MARKS

Provided at four corners of the sheet in order to facilitate trimming

These marks are in the form of right angled isosceles triangles

21

GRID REFERENCE SYSTEM

Recommended in order to permit easy location

on the drawing of details, additions or

modifications

Number of divisions should be divisible by two

Chosen in relation to the complexity of the

drawing

Length of any side of grid should not be less than

25mm and should not be more than 75mm

The rectangles of the grid should be referenced

by means of capital letters along one edge and

numerals along the other edge

The numbering may start at the sheet corner

opposite to the title block as shown in Figure 1.5

22

LINES

23

LINES

24

THICK LINE / OBJECT OUTLINES

LINES

Represented by thick line (0.7mm thickness) and is used to show the outer visible feature of the object in the drawing

HIDDEN LINES

LINES

Represented by short dashes closely and evenly spaced

Used to show the invisible or hidden parts on the drawing

CHAIN THIN DOUBLE DASHED

(PHANTOM LINES)

LINES

These Lines are used to represent the outline of an adjacent part, show alternate position of a moving part or replace repetitive details such as gear teeth and threads

LONG BREAK LINES

LINES

Represented by thin ruled line provided with free hand zig-zags at suitable intervals and is used to show the break for a considerable length of the object

SHORT BREAK LINES

LINES

Represented by thin free-hand and is used to show the break of an object for a short length

CUTTING PLANE LINE

LINES

Represented by thick long line at the ends with thin long and short lines at the centre

Used to show the edge of the cutting plane

CONTINUOUS THIN LINE

LINES

Used for showing dimension lines, extension lines, construction lines, hatching lines or section lines

CENTRE LINE

LINES

Represented by long and short dashed in proportion ranging from 6:1 to 4:1, closely and evenly spaced in any drawing

Used to show the centre line location of cylindrical, conical and spherical objects

LETTERING

Lettering on a drawing enables engineer,

architect or designer to communicate a complete

description of an object

Standard lettering for technical drawing are

called Gothic lettering

All letters in words are capitalized and squared

LETTERING

The height (h) of capital letters is taken as the base of dimensioning

Two standard ratios for d/h, 1/14 and 1/10 are used

The lettering may be vertical or inclined at 150 to the right

The proportions of different dimensions are shown below

LETTERING

For standard ratios for d/h, 1/14 different dimensions are shown below

LETTERING

For standard ratios for d/h, 1/10 different dimensions are shown below

LETTERING

Use the single-stroke, vertical, gothic style of

lettering

Use upper case (capital) letters only!

Always skip a space between rows of letters

Always use very light guide

Fraction bars are always drawn horizontal

Use a medium (B, HB, H) lead for normal

lettering

Use a hard (4H to 9H) lead for drawing guide

lines

RULES FOR LETTERING

LETTERING

Draw 2 lines parallel and write letters in it

The lines can be drawn using 2H pencil

The line must be very soft enough for our own

eyes to be seen

Line can be drawn horizontally using T Square

Firstly, determine the height (h) of the letter to

be drawn

The length between 2 line must be h mm

STEPS FOR LETTERING

h

LETTERING

VERTICAL LETTERING

LETTERING

INCLINED LETTERING

LETTERING

Don't mix capital letters with small letters (a)

Write in a form of same type of letter (b)

LETTERING

Dont mix letters which written straight with

leaning letters

LETTERING

Letter must have uniform thickness and

blackness

INCORRECT

CORRECT

45

SECTIONS

A section drawing shows the inside details of an object by cutting away part of the object

Normal multiview drawing

Normal section view

Section view drawing with

convention

SECTIONS

SECTIONS

Cutting plane lines mark the point at which the

object is to be cut apart (with dashed line)

Sight lines point to the part of the object that is

to be kept

CUTTING

PLANE LINE

SIGHT LINE

CUTTING PLANE LINES

SECTIONS

Used to show where the object has been cut

If the part was cut with a saw, the hatching

would represent where the saw actually touched

the object as it was being cut

Hatch lines should match the color of the cutting

plane line

The pattern of the hatching used represents

different types of materials

HATCHING

Hatch lines

SECTIONS

FULL SECTION

The cutting plane line cuts through the entire length, height, or width

SECTIONS

HALF SECTION

The cutting plane line cuts through only Half the length, height, or width of the object

This line divides the object so the sectioned

portion and the non-sectioned portion can

be defined.

SECTIONS

OFFSET SECTION

Offset sections allow one cutting plane line to transect multiple areas of a part

This reduces the amount of work needed to complete a drawing

SECTIONS

PARTIAL OR LOCAL SECTION

Local section is drawn if half or full section is not convenient

Local break may be shown by continuous thin free hand line

SECTIONS

REVOLVED SECTION

Cross sections may be revolved in relevant view The outline of the section should be shown with

thin continuous line inside the object as shown

SECTIONS

REVOLVED AND REMOVED SECTION

The removed section may be placed near to and connected with the view by a chain thin line (a) or in a different position and identified in the conventional manner (b)

SECTIONS

SECTIONS NOT TO BE HATCHED

INVISIBLE LINE TECHNIQUE

AXIS REPRESENTATION

59

CONVENTIONAL REPRESENTATION OF MATERIALS

60

CONVENTIONAL REPRESENTATION OF M/C COMPONENTS

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64


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Title

66


DIMENSIONING

Dimension is a numerical value expressed in

appropriate units of measurement and indicated

on drawing using lines, symbols, notes etc

As far as possible, dimensions should be placed

outside the view

Dimensions should be taken from visible outlines

rather than from hidden lines

Each feature should be dimensioned once on a

drawing

Dimensions should be placed on the view or

section that relates most clearly to the

corresponding features

Each drawing should use the same unit for all

dimensions but without unit symbol

DIMENSIONING

Dimensions should be indicated on a drawing

according to any one of the following methods;

(a) Aligned system

(b) Uni-directional system

METHODS

(b) (a)

Angular dimensions are placed so that they show the angle

of an inclined feature on a drawing

DIMENSIONING

BASIC TYPES

DIMENSIONING

BASIC TYPES

Arrowless dimensions are used in confined areas where other dimensioning methods would confuse the reader

Also arrowless dimensioning is very accurate since all features are dimensioned from an origin point or datum point

Chain dimensions are placed end to end

This practice is not as accurate as datum dimensioning because

the location of the each feature is dependent upon neighboring

features

DIMENSIONING

BASIC TYPES

Datum dimensions are placed so that all dimensions originate at the same

coordinate

This practice is accurate than chain dimensioning because the location of each

feature is independent of the other feature

DIMENSIONING

BASIC TYPES

Chart dimensioning is used when part sizes change to fit an application. In the

above example part #ADD120 may be needed: therefore a note is placed on

the drawing to indicate that the part is to be fabricated according to these

specifications.

This type of method eliminates the need to create a separate drawing for each

suitable change in design.

If new part is needed with a larger hole, that instance is added to the table with

its own part number

DIMENSIONING

BASIC TYPES

Tabular dimensioning is used to locate features on a (X,Y)

coordinate system.

In the above example a hole is identifying by a letter, and its

location is identified by a coordinate

This method saves space and avoids confusing and error

If a new hole is needed or the location is changed another hole

number may be added or the coordinate may be quickly changed

DIMENSIONING

BASIC TYPES

Radius/Diameter dimensioning is used to dimension fillets,

rounds and circles

Fillets are small inside arcs and rounds are small outside arcs

DIMENSIONING

BASIC TYPES

To avoid repetitious dimensions on a drawing the abbreviation

TYP (meaning typical) is used. When TYP appears after a size

dimension, such as a diameter, un-dimensioned circles are

intended to be the same dimension.

DIMENSIONING

BASIC TYPES

77

MEANING OF NOTES

78

DRAFTING ABBREVIATIONS

79

MATERIAL ABBREVIATIONS

Machine Drawing

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Transcript of Machine Drawing