Download - KrarUnit05
-
7/27/2019 KrarUnit05
1/29
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
PowerPoint to accompany
Krar Gill Smid
Technology of Machine Tools6th Edition
Job Planning
Section 4
-
7/27/2019 KrarUnit05
2/29
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
PowerPoint to accompany
Krar Gill Smid
Technology of Machine Tools6th Edition
Engineering Drawings
Unit 5
-
7/27/2019 KrarUnit05
3/29
5-3
Objectives
Understand the meaning of the various lines
used on engineering drawings
Recognize the various symbols used to
convey information
Read and understand engineering drawings
or prints
-
7/27/2019 KrarUnit05
4/29
5-4
Engineering Drawings
Language draftspersons, tool designers, andengineers indicate to machinist physicalrequirements of part
Three standards similar American ANSI Y14.5 (American standard)
ASME Y14.5M-1994
ISO R1 101
Complete product: Assembly drawing Each part component: detailed drawing
Reproduced as copies called prints
-
7/27/2019 KrarUnit05
5/29
5-5
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
Orthographic View
orProjection Method
Shows part from three sides
-
7/27/2019 KrarUnit05
6/29
5-6
Cylindrical Parts
Shown on prints in two views
Front and right
Interior forms difficult
Sectional view
-
7/27/2019 KrarUnit05
7/29
5-7
Standard LinesExample Name Description Use
Object lines Thick, black Edge of object
.030 in wide
Hidden lines Medium, black Hidden contours
.125 in dashes
.060 in spacesCenter lines Thin lines Centers of holes
long-short
Dimension Thin double Dimensions
arrowCutting-plane Thick black Show imagined
long, two short section cut
Cross section Fine, parallel Show surfaces
45 degrees exposed (cut)
1
-
7/27/2019 KrarUnit05
8/29
5-8
Drafting Terms
Limits
Largest and smallest
permissible dimensions
Copyright The McGraw-Hill Companies, Inc.Permission required for reproduction or display.
Tolerance
Permissible variation ofsize of the part
largest
smallest
Example: .001+.003=.004
-
7/27/2019 KrarUnit05
9/29
5-9
Drafting Terms
Allowance
Intentional difference in sizes of mating parts
Shop drawing would show both shaft and holewith max and min sizes to produce best fit
Fit
Range of tightness between two mating parts
Two general classes
Clearance fits: part revolve or move
Interference fits: two parts forced together as single
-
7/27/2019 KrarUnit05
10/29
5-10
Scale Size
Indicates scale to which drawing has beenmade
Representative measurement
Scale Definition
1:1 Actual size of part
1:2 One-half actual size of part
2:1 Twice actual size of part
-
7/27/2019 KrarUnit05
11/29
5-11
Units of Measurement
Metric system of measurement is
international standard
Inch system widely used in US and Canada
Note on title block of drawing should
identify: inch, metric, or dual
-
7/27/2019 KrarUnit05
12/29
5-12
Manufacturing Methods
Drawing only defines part
Does not specify how part made
Example: Hole diameter shown
Does not indicate drill, ream, bore
Tolerance or limit should be provided if
dimension is critical
-
7/27/2019 KrarUnit05
13/29
5-13
Basic Dimensioning
Used on working drawings to explain to
machinist shapes and sizes required
Title block
Type of material
Number of parts required
Special notes
-
7/27/2019 KrarUnit05
14/29
5-14
Dimensioning Tolerances
Define accuracy of specific operation or part
Each dimension should have tolerance
Tolerance on dimension as 1 or 2 units of
last digit
.6783 indicates tolerance of .0001 in.
Can show specific limits (high or low) or as
plus or minus tolerancing
-
7/27/2019 KrarUnit05
15/29
5-15
Inch Dimensions
Fractions sizes stated to two decimal places
indicates not critical size
Whole dimensions shown with minimum of
two zeros to right of decimal point
No zero used to left of decimal for values
less than 1 in.
Critical dimensions shown in three or four
decimal places and tolerances included
-
7/27/2019 KrarUnit05
16/29
5-16
Metric Dimensions
Zero must be used to left of decimal for
sizes less than 1 millimeter
No decimal point or zero follows whole
number
Where dimension larger than whole number
by decimal fraction, last digit to right of
decimal point is NOT followed by zero
-
7/27/2019 KrarUnit05
17/29
5-17
Common Symbols
angularity countersink
basic dimension depth/deep
between diameter
conical taper perpendicularity
counterbore/spotface radiusR
60
-
7/27/2019 KrarUnit05
18/29
-
7/27/2019 KrarUnit05
19/29
5-19
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
-
7/27/2019 KrarUnit05
20/29
5-20
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
-
7/27/2019 KrarUnit05
21/29
5-21
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
-
7/27/2019 KrarUnit05
22/29
5-22
Dimensioning Systems
Dimensions used on prints to give distancebetween two points, lines, planes
Numerical value gives actual measurement Dimension line indicates direction
Arrowheads indicate points between whichvalue applies
Decimal system uses only decimal fractions
5 23
-
7/27/2019 KrarUnit05
23/29
5-23
Dimensioning Systems
Two types used in computer numerical
control work
Incremental system
Dimensions given from previously known point
Absolute system
Dimensions or positions given from fixed zero ororigin point
5 24
-
7/27/2019 KrarUnit05
24/29
5-24
Workplace Communication
Manufacturing part of global economy
Standardized symbols and characteristics
International Standards Organization (ISO) Established in 1946
TC#10 committee to develop standards fortechnical drawings
American Society of Mechanical Engineers(ASME) ASME Y14.5-1994 publication on
Dimensioning and Tolerancing lists lateststandards
5 25
-
7/27/2019 KrarUnit05
25/29
5-25
Common Machine Shop
Abbreviations
CBORE Counterbore
CSK Countersink
DIA DiameterDiameter
HDN Harden
L Lead
LH Left hand
mm Millimeter
NC National coarse
NF National fine
P Pitch
R Radius
Rc Rockwell hardness testRH Right hand
THD Thread or threads
TIR Total indicated runout
TPI Threads per inch
UNC Unified national coarse
UNF Unified national form
5 26
-
7/27/2019 KrarUnit05
26/29
5-26
Surface Symbols
Deviation from nominal surface caused by
machining operation
Includes roughness, waviness, lay, and flaws
Measured by surface finish indicator in
microinches (in.)
Surface finish mark Indicates which surface of part to finish
5 27
-
7/27/2019 KrarUnit05
27/29
5-27
Surface Finish Mark
40
.002
.001
Waviness height in
thousandths of an inch
Machining marks runperpendicular to the
boundary of the surface
indicated
Surface finish
in microinches
Roughness width in
thousandths of an inch
5 28
-
7/27/2019 KrarUnit05
28/29
5-28
Surface Symbols
Indicate direction of lay
Marks produced by machining operations onwork surfaces
= Parallel to boundary line of surfaceindicated by symbol
X Angular in both directions on surface
indicated by symbol
M MultidirectionalC Approximately circular to center of
surface indicated by symbol
R Approximately radial to center of
surface indicated by symbol
5 29
-
7/27/2019 KrarUnit05
29/29
5-29
Material Surfaces
Cast iron and malleable ironAluminum, magnesium
and their alloys
Copper, brass
bronze, etc.
Steel and wrought iron