quest kss engineering drawings
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Aerospace Civil Structures Industrial Energy Transportation
Engineering Drawing
Prepared by : Ajitanath
QuEST, Bangalore,
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Contents
Why Engineering Drawings?
Projections
Plan your drawing & views
Lines and line styles
Sectional views, Types & Best practice
Dimensioning
Types of dimensioning & Best practice
ISO limits and fits
Conventional representation of parts
Abbreviations of terms frequently used on drawings
Tips on Thread Assemblies
Assembly Drawings
Trend…
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Why Engineering Drawings?
The main purpose of engineering drawings is to communicate to other
engineers, machinists, etc.
Engineering drawing is a formal and precise way of communicating information
about the shape, size, features and precision of physical objects. (Also specifies
material, define processes like heat treatment, surface treatment, welding specs,
etc)
Drawing is the universal language of engineering.
Just like written language has standards, the “grammar” of technical drawing is
defined by...
the ANSI Y14.5 or the ISO standard or so…
These standards must be understood to draw & read a drawing.
Drawings do the communication best merely because a picture is worth a
thousand words. Engineers are very picky about their drawings and must pay
attention to detail.
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Projections
Back in the 18th century a French mathematician and engineer, Gaspard Monge
(1746-1818), was involved with the design of military armoury. He developed a
system, using two planes of projection at right angles to each other, for graphical
description of solid objects.
This system, which was,
and still is, called Descriptive Geometry.
Monge's Descriptive Geometry
forms the basis of what is now called
Orthographic Projection.
The word orthographic means to draw at right angles and is derived from the Greek
words: ORTHOS - straight, rectangular, upright
GRAPHOS - written, drawn
Projections created with the object placed in the first quadrant are
said to be in First Angle projection, and likewise, projections
created with the object placed in the third quadrant are said to
be in Third Angle projection.
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Projections...
Both systems of projection, First and Third
angle, are approved internationally and have
equal status. The system used must be clearly
indicated on every drawing, using the
appropriate symbol shown in figure.
First Angle projection is more common in
Europe.
Third Angle projection is widely used in both
the USA and the UK.
Projection system symbols
and recommended
proportions
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Plan your drawing & views
Before starting your engineering drawing you
should plan how you are going to make best
use of the space. It is important to think about
the number of views your drawing will have
and how much space you will use of the
paper.
Always use the appropriate & standard drawing size &
sheets.
Use recommended standard scale to the drawing.
Try to make maximum use of the available space.
Place minimum two-three appropriate views in the
planed space.
If a view has lots of detail, try and make that view as
large as possible. If necessary, draw that view on a
separate sheet.
If you intend to add dimensions to the drawing,
remember to leave enough space around the drawing
for them to be added later.
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Lines and line styles
The lines we created were all of the same thickness and type. But lines on an
engineering drawing signify more than just the geometry of the object and it is
important that you use the appropriate line types.
Line Thickness : For most engineering drawings you will require two thickness', a thick and
thin line. The general recommendation are that thick lines are twice as thick as thin lines.
A thick continuous line is used for visible edges and outlines.
A thin line is used for hatching, leader lines, short centre lines, dimensions and projections.
Line Styles : Other line styles used to clarify important features on drawings are:
Thin chain lines are a common feature on engineering drawings used to indicate centre lines.
Centre lines are used to identify the centre of a circle, cylindrical features, or a line of symmetry.
Dashed lines are used to show important hidden detail for example wall thickness and holes.
etc..
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Lines and line styles...
Continuous Visible outlines
0.7mm
Continuous (thin) Dimension lines
0.3mm
Short dashes Hidden detail 0.3mm
Long chain Center lines
0.3mm
Chain, thick at ends Section cutting planes
0.7 – 0.3mm
Short chain Developed views
0.3mm
Continuous wavy Broken boundaries
0.3mm
Straight zigzag Break lines 0.3mm
Straight lines with Dimension lines two short zigzags 0.3mm
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Lines and line styles...
Applications of the various types of lines Some good practices
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Sectional views & Types
Sectional views are produced to:
• clarify details
• show internal features clearly
• reduce number of hidden detail lines required
• aid dimensioning
• show cross-section shape
• clarify an assembly
Surfaces cut by the cutting plane are
usually hatched at an appropriate
angle, say 45° with a density of lines
in proportion with the component.
Which Sectional View?
Sectional View in a single
plane Sectional View in two
planes
Half Sectional views Part Sectional views
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Sectional views & Best practice
Note:
• Revolved sections.
• Part sections.
• Different hatching directions and spacing's.
• Un-sectioned components such as shafts, keys, nuts all standard pats like motors, etc.
An assembly drawing view, clarified sections, where to hatch & hatch pattern
Wrong!
Web is not
sectioned.
Correct
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Sectional views & Best practice…
The cross-section on the right of figure is technically correct. However, the convention
in a drawing is to show the view on the left as the preferred method for sectioning this
type of object.
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Dimensioning
General rules.
Standards and conventions should be followed.
Dimensions should be placed on drawings so that they may be easily read.
The drawing must include the minimum number of dimensions required to accurately manufacture the design.
A dimension should not be stated more than once, unless it aids communication.
It should not be necessary for the operator manufacturing the component to have to calculate any dimensions.
Types of dimension.
Size dimensions: Used to describe heights, widths, diameters, etc.
Location dimensions: Used to place various features of a component relative to each other, such as a hole centre line to a reference surface.
Mating dimensions: Used for parts that fit together requiring a certain degree of accuracy
Dimensions have four basic components:
1. Dimension Text 2. Dimension Line and Arrows
3. Extension Lines 4. Gap
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Dimensioning…
An Overview
Dimensions are always drawn
using continuous thin lines.
Two projection lines indicate
where the dimension starts
and finishes. Projection lines
do not touch the object and
are drawn perpendicular to the
element you are dimensioning.
All dimensions less than 1
should have a leading zero.
i.e. .35 should be written as
0.35
Edges A and B are being used
as the reference edges
Minimum number of
dimensions required are
specified
Evenly spaced dimension lines
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Types of dimensioning
Parallel Dimensioning Superimposed Running Dimensions Chain Dimensioning
Combined Dimensions Dimensioning by Co-ordinates Simplified dimensioning by co-ordinates
Dimensioning circles
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Dimensioning… & Best practice
The simple bearing bracket casting shows
both size and location dimensions
Example of appropriate and
inappropriate dimensioning
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Dimensioning… & Best practice…
(D) ARROW AND TEXT PLACEMENT
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Dimensioning … Which is better?
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Dimensioning … Which is better?
A Dimensioning Example, showing that placement should match
intent :
These drawings show bolts holes for mounting a flange onto a plate. When
mounting the flange, the position of the holes with respect to each other is very
important, or else the flange (or part) won’t fit. It makes sense to dimension the
distance between the holes, instead of the distances to the edge.
Dimension placement matches intent Dimension placement does NOT
match intent
0.753
0.747
0.756
0.744
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Tabulated guide to types of ISO limits and fits.
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Conventions
Conventional Breaks are a way of
depicting a very long object without
showing the entire length. It is often
used for objects like rods,
tubing/piping or wooden objects.
Here are some examples of
commonly used engineering
components and features of
components.
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Conventional representation of parts
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Abbreviations of terms frequently used on drawings
A/F Across flats
HEX HD Hexagon head
ASSY Assembly
CL Center line
CHAM Chamfer
CH HD Cheese head
CSK Counter sunk
CBORE Counter bore
CYL Cylinder or cylindrical
DIA Diameter (in a note)
Ø Diameter (preceding a dimension)
R Radius (preceding a dimension, capital only)
RAD Radius (in a note)
DRG Drawing
LH Left hand
MATL Material
NO. Number
PATT NO. Pattern number
PCD Pitch circle diameter
I/D Inside diameter
O/D Outside diameter
RH Right hand
SQ Square (in a note)
TYP Typical or typically
THK Thick
Square (preceding a dimension)
STD Standard
UCUT Undercut
M/CD Machined
mm Millimeter
NTS Not to scale
RPM Revolutions per minute
SWG Standard wire gauge
TPI Teeth per inch
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Tips on Thread Assemblies
Note that the tapped hole is
sectioned, the fastener is not.
Observe the types of holes
& how they machined.
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Assembly Drawings
The assembly of the parts is shown in an assembly drawing also known as a general
arrangement
Features of an assembly drawing
• Assembly views (with c/s views)
• Exploded views (if required)
• Dimensions
• Internal Parts
• Parts list
• Ballooning
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Assembly Drawings…
Examples of Assembly Drawings
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
Trend…
The graph below gives a very crude indication of the productivity of companies
developing CAD software, through time.
As time passes more and more 3D CAD software packages allow you to create
high quality photorealistic images of your designs.
© 2012, Quality Engineering and Software Technologies, Inc. All rights reserved. UNCONTROLLED WHEN PRINTED
QuEST Recognition
Ranked 2nd among ESOs in 2006 Black Book of Outsourcing
Ranked among Top Emerging Service Providers in 2007 Global Services 100
Listed in IAOP’s 2007 Global Outsourcing 100
Listed in Deloitte’s Technology Fast 500 companies in Asia Pacific
UT500 Preferred Supplier
Supplier Excellence Award from GE
Thank you. For more information:
Presenter name: Ajitanath Patil
Title:
E: email address: ajitanath.patil@quest-global.com
M: contact no. 91-80-41190900
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