chapter 16 geometric dimensioning and tolerancing engineering drawing and design engineering drawing...
TRANSCRIPT
Chapter 16Chapter 16
Geometric Dimensioning
and Tolerancing
EngineeringDrawing and Design
EngineeringDrawing and DesignSeventh EditionSeventh Edition
GD&T stands for Geometric Dimensioning & Tolerancing
DIMENSION is a geometric characteristic the size of which is specified such as length,angle,location,or center distanceTOLERANCE on a dimension is the total permissible variation in its size, which is equal to the difference between the limits of size.
GEOMETRIC DIMENSIONING AND TOLERANCING
DIMENSIONS OF A PART
GEOMETRIC DIMENSIONING AND TOLERANCING
TOLERANCE SIZES
GEOMETRIC DIMENSIONING AND TOLERANCING
TYPE OF TOLERANCE
GEOMETRIC DIMENSIONING AND TOLERANCING
SIZES OF MATING PARTS
Deviations
The difference between the basic size and the maximum and minimum sizes are called the UPPER & LOWER deviations.The BASIC DIMENSION represents the theoretical exact size or location of a feature.
GEOMETRIC DIMENSIONING AND TOLERANCING
DEVIATIONS
GEOMETRIC DIMENSIONING AND TOLERANCING
BASIC (EXACT) DIMENSIONSAre shown in a rectangle to indicate that the tolerances in the general tolerance note do not apply
Datum
A DATUM is a theoretical exact feature from which dimensions may be taken.A DATUM is generally chosen as an edge or feature which has the greatest influence in a specific measurement.
GEOMETRIC DIMENSIONING AND TOLERANCING
EXAMPLES OF DEVIATION OF FORM WHEN PERFECT FORM AT THE MAXIMUM MATERIAL CONDITION IS REQUIRED
GEOMETRIC DIMENSIONING AND TOLERANCING
EXAMPLES OF DEVIATION OF FORM WHEN PERFECT FORM AT THE MAXIMUM MATERIAL CONDITION IS REQUIRED
Geometric Tolerance
A geometric tolerance is the maximum permissible variation of form, profile, orientation, location, and runout from that indicated or specified on a drawing.Feature control frame for an individual feature is divided into compartments containing, at the least, the geometric tolerance symbol and the geometric tolerance value
Feature control frame (fig.16-16)
Geometric characteristic symbolGeometric toleranceDatums (if used)Modifiers as required (*MMC for example)
GEOMETRIC DIMENSIONING AND TOLERANCING
GEOMETRIC CHARACTERISTIC SYMBOLS
16-216-5
STRAIGHTNESSFORMINDIVIDUAL
FEATURES
SEE UNITSYMBOLCHARACTERISTIC
TYPE OFTOLERANC
EFEATURE
GEOMETRIC DIMENSIONING AND TOLERANCING
GEOMETRIC CHARACTERISTIC SYMBOLS
16-4MAXIMUMMATERIALCONDITION
SUPPLEMENTARYSYMBOLS
SEE UNIT
SYMBOLCHARACTERISTIC
TYPE OFTOLERANC
E
FEATURE
GEOMETRIC DIMENSIONING AND TOLERANCING
GEOMETRIC CHARACTERISTIC SYMBOLS
16-4LEASTMATERIALCONDITION
SUPPLEMENTARYSYMBOLS
SEE UNIT
SYMBOLCHARACTERISTIC
TYPE OFTOLERANC
E
FEATURE
GEOMETRIC DIMENSIONING AND TOLERANCING
GEOMETRIC CHARACTERISTIC SYMBOLS
16-9PROJECTED TOLERANCE
ZONE
SUPPLEMENTARYSYMBOLS
SEE UNIT
SYMBOLCHARACTERISTIC
TYPE OFTOLERANC
E
FEATURE
GEOMETRIC DIMENSIONING AND TOLERANCING
GEOMETRIC CHARACTERISTIC SYMBOLS
16-916-11
BASIC DIMENSION
SUPPLEMENTARYSYMBOLS
SEE UNIT
SYMBOLCHARACTERISTIC
TYPE OFTOLERANC
E
FEATURE
GEOMETRIC DIMENSIONING AND TOLERANCING
GEOMETRIC CHARACTERISTIC SYMBOLS
16-6DATUMFEATURE
SUPPLEMENTARYSYMBOLS
SEE UNIT
SYMBOLCHARACTERISTIC
TYPE OFTOLERANC
E
FEATURE
GEOMETRIC DIMENSIONING AND TOLERANCING
GEOMETRIC CHARACTERISTIC SYMBOLS
16-11DATUMTARGET
SUPPLEMENTARYSYMBOLS
SEE UNIT
SYMBOLCHARACTERISTIC
TYPE OFTOLERANC
E
FEATURE
Form Tolerances
FORM TOLERANCES control the straightness, flatness, circularity and cylindricityForm tolerances apply to individual features and as such do not require locating dimensions.ORIENTATION TOLERANCES control angularity, parallelism, and perpendicularity
More on FORM TOLERANCES
Straightness-a condition in which the element of a surface or a median line is a straight lineFlatness of a surface is a condition in which all surface elements are in one plane
GEOMETRIC DIMENSIONING AND TOLERANCING
FEATURE CONTROL FRAME
GEOMETRIC DIMENSIONING AND TOLERANCING
APPLICATION OF FEATURE CONTROL FRAME
ATTACHED USING A LEADER
MMC, RFS, LMC applies to features subject to variations in size
MMC (Maximum Material Condition) is when a feature or part is at the limit of size, which results in its containing the maximum amount of material.LMC (Least Material Conditon) refers to the size of a feature that results in the part containing the minimum amount of material. Thus it is the minimum limit of size for an external feature.RFS (Regardless of feature size) indicates that a geometric tolerance applies to any size of a feature that lies within its size tolerance.
Datums and the 3-plane concept (16-5)
Datum is a theoretical point, line, plane, or other geometric surface fromwhich dimensions are measured when so specified or to which geometric tolerances are referencedDatum feature is a feature of a part, such as a surface, that forms the basis for a datum or is used to establish its location
3-plane system
The three planes constitue a datum system from which measurements can be taken. They will appear on the drawing.Datum feature symbol is used on the drawing to identify these surfaces
GEOMETRIC DIMENSIONING AND TOLERANCING
THE DATUM PLANES
GEOMETRIC DIMENSIONING AND TOLERANCING
THE DATUM PLANES
GEOMETRIC DIMENSIONING AND TOLERANCING
THE DATUM PLANES
Orientation tolerancing (16-6)
Angularity, parallelism and perpendicularity are orientation tolerances applicable to related features
Angularity is the condition of a surface or axis at a specified angle (other than 90 or 0 ) from a datum ⁰ ⁰plane or axis
Perpendicularity is the condition of a surface at 90 to ⁰a datum plane or axis. *A perpendicularity tolerance for a flat surface specifies a tolerance zone defined by two parallel planes perpendicular to a datum plane or axis
Parallelism is the condition of a surface equidistant at all points from a datum plane. Parallelism for a flat surface specifies a tolerance zone defined by two planes or lines parallel to a datum plane or axis.
Datum Targets (16-11)
Datum target symbols are used to locate specific reference positions to be used on large datum surfaces*the surface of a feature may be so large that a gage designed to make contact with the full surface may be too expensive or cumbersome to useFunctional requirements of the part may necessitate the use of only a portion of a surface as a datum feature
CAD APPLICATIONS
TOLERANCE DIALOG BOX
CAD APPLICATIONS
TOLERANCE SYMBOL DIALOG BOX