CHAPTER 10
Dimensioning and
Tolerancing
Learning Objectives
• Identify and use common dimensioning
systems
• Explain and apply dimensioning standards
based on ASME Y14.5-2009
• Apply proper specific notes for
manufacturing features
• Place proper general notes and flag notes
on a drawing
• Interpret and use correct tolerancing
techniques
Learning Objectives
• Prepare completely dimensioned
multiview drawings from engineering
sketches and industrial drawings
• Apply draft angles as needed to a
drawing
• Dimension CAD/CAM machine tool
drawings
• Prepare casting and forging drawings
Learning Objectives
• Provide surface finish symbols on
drawings
• Solve tolerance problems including limits
and fits
• Use an engineering problem as the basis
for your layout techniques
• Describe the purpose of ISO 9000 Quality
Systems Standard and related standards
Dimensions
• Required on detail drawings
• Provide shape and size description
• Size dimensions
• Location dimensions
• Notes
 Local
notes (specific notes)
 General notes
Dimensions
ASME Dimensioning Standards
• ASME Y14.5, Dimensioning and
Tolerancing
• General note: DIMENSIONING AND
TOLERANCING PER ASME Y14.5-2009
• Several other ASME documents with
standards related to dimensioning and
tolerancing
Dimensioning Definitions
•
•
•
•
•
•
•
Actual size
•
Allowance
•
Basic dimension
Bilateral tolerance •
Datum
•
Diameter
Feature
Feature of size
Geometric
tolerance
Least material
condition (LMC)
Limits of
dimension
Dimensioning Definitions
• Maximum material •
condition (MMC)
• Nominal size
•
• Radius
•
• Reference
dimension
• Stock size
Specified
dimension
Tolerance
Unilateral
tolerance
Fundamental ASME Y14.5
Dimensioning Rules
• Each dimension has a tolerance except
reference, maximum, minimum, or stock
• Dimensioning and tolerancing must be
complete
• Show each necessary dimension of an end
product
• Select and arrange dimensions to suit the
function and mating relationship of a part
Fundamental ASME Y14.5
Dimensioning Rules
• Dimensions must not be subject to more
than one interpretation
• Do not specify the manufacturing
processes unless necessary
• Identify nonmandatory dimensions with
an appropriate note
• Arrange dimensions to provide required
information and optimum readability
• Show dimensions in true profile views and
visible outlines
Fundamental ASME Y14.5
Dimensioning Rules
• Dimension diameter or thickness of materials
manufactured to gage or code numbers
• 90°angle is implied for centerlines and lines
• 90°basic angle is implied for centerlines
located by basic dimensions
• A zero basic dimension applies where axes,
center planes, or surfaces are shown one over
the other with established geometric controls
Fundamental ASME Y14.5
Dimensioning Rules
• Unless otherwise specified, all:
• Dimensions and tolerances are measured
•
•
•
at 20°C (68°F)
Dimensions and tolerances apply in a free
state condition except for nonrigid parts
Tolerances apply for the full depth,
length, and width of the feature
Dimensions and tolerances apply on the
drawing where specified
Fundamental ASME Y14.5
Dimensioning Rules
• Coordinate systems:
• Right-handed (arranged clockwise)
• Labeled axes and positive direction shown
• 3-D model complies with ASME Y14.41,
Digital Product Definition Data
Practices
Dimensioning Components
Dimensioning Symbols
Unidirectional Dimensioning
• Numerals, figures,
and notes lettered
horizontally
• Read from the bottom
of the drawing sheet
• Mechanical drafting
for manufacturing
Aligned Dimensioning
• Numerals, figures, • Architectural and
and notes aligned
structural drafting
with the dimension
lines
• Horizontal dimensions 0
•
read from the bottom
Vertical dimensions
read from the right
side
Rectangular Coordinate Dimensioning
without Dimension Lines
• Ordinate dimensioning
• Dimension values aligned with extension
lines
• Dimension represents a measurement
originating from datums or coordinates
• Features such as holes sized using specific
notes or a table
• Popular for:
• Precision sheet metal part drawings
• Electronics drafting
Rectangular Coordinate Dimensioning
without Dimension Lines
Tabular Dimensioning
• Form of rectangular coordinate
dimensioning without dimension lines
• Features dimensioned in a table
Chart Dimensioning
• Used when a part or assembly has one
or more dimensions that change
depending on the specific application
Millimeter Dimensions
• Millimeters (mm)
• Common International
System of Units (SI) unit of
measure
• General note: UNLESS
OTHERWISE SPECIFIED,
ALL DIMENSIONS ARE IN
MILLIMETERS
• Follow any inch
dimensions with IN
Proper Use of Metric Units
• Omit decimal point and 0 when
dimension is a whole number
• Precede a decimal value that is less
than 1 with a 0
• When the value is greater than a whole
number by a fraction of a mm, do not
place a 0 next to last digit
• Exception: when displaying tolerance
values
Proper Use of Metric Units
• Plus and minus tolerance values have
same number of decimal places
• Limit tolerance values have same
number of decimal points
• Unilateral tolerances use a single 0
without a corresponding + or – sign
Inch Dimensions
• Decimal inches (IN)
• United States (U.S.)
customary unit of measure
• General note: UNLESS
OTHERWISE SPECIFIED,
ALL DIMENSIONS ARE IN
INCHES
• Follow any millimeter
dimensions with mm
Proper Use of Inch Units
• Do not precede a value that is less
than 1 inch with a 0
• Express a specified dimension to the
same number of decimal places as its
tolerance
• Fractional inches generally indicate
larger tolerance
Proper Use of Inch Units
• Plus and minus tolerance values have
the same number of decimal places
• Unilateral tolerances use the + and –
sign
• The 0 value has the same number of
decimal places as the value that is greater
or less than 0
• Limit tolerance values have the same
number of decimal points
Proper Use of Angular Units
• Use decimal or degrees–
minutes–seconds format
• Angle and tolerance
values have the same
number of decimal
places
• Include 0°or 0°0″
when specifying only
minutes or seconds, as
applicable
Using Fractions
• Not as common as decimal inches or
millimeters
• Architectural and structural drawings
• Generally indicate larger tolerance
Arrowheads
•
•
•
•
Terminate dimension lines and leaders
Three times as long as they are wide
Consistent size
Filled in solid or open
Dimension Line Spacing
• First dimension line:
• Uniform distance from the object
 .375
in. (10 mm) minimum
 .5 - 1.0 in. (12 - 24 mm) preferred
• Succeeding dimension lines:
• Equally spaced
 .25
in. (6 mm) minimum
 .5 - .75 in. (12 - 20 mm) preferred
Dimension Numerals
Chain Dimensioning
• Creates tolerance stacking (tolerance
buildup)
• Omit one intermediate dimension or the
overall dimension
Baseline Dimensioning
• Size or location of features controlled
from a common reference plane
• Reduces possibility of tolerance
stacking
Direct Dimensioning
• Results in the least tolerance stacking
Dimensioning Symmetrical Objects
Dimensioning Cylinders
Dimensioning Square Features
Preferred Dimensioning Practices
• Avoid crossing extension lines
• Do not break extension lines when they
cross
• Never cross extension lines over
dimension lines
• Break the extension line where it
crosses over a dimension line when
necessary
Preferred Dimensioning Practices
• Never break a dimension line
• Break extension lines when they cross
over or near an arrowhead
• Avoid dimensioning over or through the
object
• Avoid dimensioning to hidden features
Preferred Dimensioning Practices
• Avoid long extension lines
• Avoid using any line of the object as an
extension line
• Dimension between views when
possible
• Group adjacent dimensions
Preferred Dimensioning Practices
• Dimension to views that provide the
best shape description
• Do not use a centerline, extension line,
phantom line, visible object line, or a
continuation of any of these lines as a
dimension line
• Stagger adjacent dimension numerals
so they do not line up
Dimensioning Angular Surfaces
Dimensioning Chamfers
Dimensioning Conical Shapes
Dimensioning Hexagons and Other
Polygons
• Dimension across the flats
Dimensioning Arc Radius
Dimensioning Arc Length
Additional Radius Dimensioning
Applications
• True radius
• TRUE R followed by the actual radius
• Controlled radius
• CR followed by the radius
• Spherical radius
• SR followed by the radius
Dimensioning Contours Not
Defined as Arcs
• Dimension coordinates or points along
the contour from common surfaces
• Series of dimensions on the object and
along the contour
• Tabular dimensioning
Locating a Point Established by
Extension Lines
Dimensioning Circles and Thru
Holes
Dimensioning Blind Holes
Dimensioning a Counterbore
Dimensioning a Spotface
Countersink or Counterdrill
Dimensioning Multiple Features
• Number of features, X, a space,
feature specification
• Dimension to one of the features only
• Examples:
• 4X Ø6 THRU or 4X Ø6
• 2X R.50
• 3X 8X45°
Dimensioning Slots
Dimensioning Keyseats and Keyways
Dimensioning Knurls
Dimensioning Necks and Grooves
Rectangular Coordinate
Dimensioning
Polar Coordinate Dimensioning
Dimensioning Repetitive Features
Locating Multiple Tabs in a Polar
Orientation
Locating Multiple Features of
Nearly the Same Size
Specifying Dimension Origin
• Clearly identifies from which feature
the dimension originates
Dimensioning Auxiliary Views
General Notes and Specifications
• Sheet blocks:
• Outside sheet blocks:
• Material
• Machining practices
• General tolerances
• Common dimensions
• Scale
• Finish or other
treatments
• Part name
• Sheet size
• Part number
• Number of revisions
• Projection
Flag Notes
• Delta note
• Specific note placed with general notes
• Keyed to the drawing
 Delta
symbol (Δ) common
 Hexagons and circles also used
Tolerances
• Help ensure parts fit together and
function in an assembly
• Apply to all dimensions on a drawing,
except:
• Reference
• Maximum
• Minimum
• Stock size
Plus-Minus Dimensioning
• Calculate the upper and lower limits from the specified
dimension and plus-minus tolerance
• Bilateral tolerance
• Most common tolerancing method
• Equal bilateral tolerance
[Insert 6.5  0.2, match to unequal bilateral tolerance
style]

Often preferred by manufactures
• Unequal bilateral tolerance
[Insert
]
Unilateral Tolerance
[Insert
, match to unequal
bilateral tolerance style]
• Used by some companies to define fits
between mating parts
• Often avoided by CNC machine
programmers
Limit Dimensioning
• Calculate the tolerance from the upper
and lower limits
• Common for defining fits between
mating parts
• Preferred by some companies or
departments
Single Limits
• Can be used for common machine
processes
• Follow dimension value with (MIN) or
(MAX)
• Design determines unspecified limit
Specified and Unspecified Inch
Tolerances
Specified and Unspecified Metric
Tolerances
• ISO 2768 classes of
size tolerances:
• Fine (f)
• Medium (m)
• Coarse (c)
• Very coarse (v)
Applying Statistical Tolerancing
Maximum Material Condition
(MMC)
• External feature is at MMC at its
largest limit
• Internal feature is at MMC at its
smallest limit
Least Material Condition (LMC)
• External feature is at LMC at its
smallest limit
• Internal feature is at LMC at its largest
limit
Clearance Fit
Allowance
MMC Internal Feature
– MMC External Feature
Allowance
Interference Fit
• Force or shrink fit
• Examples:
• Bushing pressed onto a housing
• Pin is pressed into a hole
Extreme Form Variation
• Established by limits of size
• Specified by “Rule 1” in ASME Y14.5
Limits and Fits Between Mating
Parts
• Fit determined first based on the use or
service
• Limits of size established second to
ensure the desired fit
• ANSI/ASME B4.1 Preferred Limits and Fits
for Cylindrical Parts
• ANSI/ASME B4.2 Preferred Metric Limits
and Fits
• Tables of establishing dimensions for
standard ANSI fits
Running and Sliding Fits (RFC)
•
•
•
•
•
•
•
RC1—Close sliding fits
RC2—Sliding fits
RC3—Precision running fits
RC4—Close running fits
RC5 and RC6—Medium running fits
RC7—Free running fits
RC8 and RC9—Loose running fits
Locational Fits (LC, LT, LN)
• LC—Locational clearance fits
• LT—Locational transition fits
• LN—Locational interference fits
Force Fits (FN)
•
•
•
•
FN1—Light drive fits
FN2—Medium drive fits
FN3—Heavy drive fits
FN4 and FN5—Force fits
Dimensions Applied to Platings
and Coatings
• General note:
• DIMENSIONAL LIMITS APPLY BEFORE (AFTER)
PLATING (COATING)
• Specific note:
• Leader with a dot pointing to the specific surface
instead of an arrowhead
Casting Drawing and Design
• Depends on:
• Casting process and characteristics
• Material
• Design or shape of the part
• Die or mold
• Based on ASME Y14.8, Castings and
Forgings standard
Shrinkage Allowance
• Extra material to account for cooling
• Examples:
• Iron .125 in. per ft. (.4 mm per meter)
• Steel .250 in. per ft.
• Aluminum .125 to .156 in. per ft. (.4 mm–.5
per meter)
• Brass .22 in. per ft. (.7 mm per meter)
• Bronze .156 in. per ft. (.5 mm per meter)
• Patternmaker applies shrink rules
Draft
• Not necessary on horizontal surfaces
• Begin at the parting line and parting
plane
• Tapers away from the molding material
Draft on a Drawing
• General note:
• ALL DRAFT ANGLES .010
• ALL DRAFT ANGLES 6°
• Angular dimensions
• Plus draft and/or minus draft methods
Parting Lines on a Drawing
Fillets and Rounds in Casting
• Allow the pattern to eject freely from
the mold
• Fillets help reduce the tendency of
cracks to develop during shrinkage
• Radii determined by part thickness
Machining Allowance
• Extra material for any surface to be
machined
• Examples:
• Iron and steel .125 in. (3 mm)
• Brass, bronze, and aluminum .062 in. (1.5
mm)
• Greater for large castings or those with
a tendency to warp
Casting Drawings
• Casting drawing
• Machining drawing
• Combined casting and machining
drawing
• Drawing phantom lines to show
machining allowance and draft angles
Forging Design and Drawing
• Focuses on dies
• Draft
• Fillets and rounds
• Machining allowance
• Based on ASME Y14.8, Castings and
Forgings standard
Forging Drawings
• Stock material drawings:
• Show size and shape of the stock material
• Outline of the end product using phantom
lines
• Detail drawings
• Show the end product
• Usually show draft
• Use phantom lines to show machining
allowance and draft angles
Surface Finish (Surface Texture)
• Obtained by:
• Machining
• Grinding
• Honing
• Lapping
• Specified using surface finish symbol
Surface Finish Characteristics
•
•
•
•
Roughness
Waviness
Lay
Flaws
Surface Finish Symbol
Design and Drafting of Machined
Features
• Capabilities of the machinery available
• Least-expensive method to get the
desired result
• Avoid over-machining
Tool Design
• Jig and fixture design
• Machining operations require special tools
to hold the workpiece or guide the
machine tool
• Involves knowledge of:
• Kinematics
• Machining operations
• Machine tool function
• Material handling
• Material characteristics
Jig and Fixture Drawings
• Assembly drawing with all components
of the tool
• Fast-acting clamps
• Spring-loaded positioners
• Clamp straps
• Quick-release locating pins
• Handles
• Knobs
Jig and Fixture Drawings
Tools in Manufacturing
•
•
•
•
•
•
•
Drill jigs
Datums
Drill fixtures
Machining fixtures
Welding fixtures
Inspection fixtures
Progressive dies
Qualities of Tools
•
•
•
•
•
Reliability
Repeatability
Ease of use
Ease of manufacture
Ease of maintenance and repair
Basic Elements of Tool Design
1. Visualizing how shop personnel will
accomplish a specific task
2. Conceptualizing hardware to assist in
the accomplishment of that task
3. Creating drawings so the hardware
can be manufactured
Introduction to ISO 9000
• ISO 9000-1
• Direction and definitions that describe what each
•
standard contains
Assists companies in the selection and use of the
appropriate ISO standard
• ISO 9001
• Model for designing, documenting, and
implementing ISO standards
• ISO 9002
• ISO 9001 but does not contain the requirement of
documenting the design and development process
Introduction to ISO 9000
• ISO 9003
• Companies or organizations that only need
to demonstrate through inspection and
testing methods that they are providing
the desired product or service
• ISO 9004-1
• Set of guidelines for development and
implementation of a quality management
system