Data Analysis Lab

ME 288Fall 2009

L6 b

GD & TGeometric Dimensioning and Tolerancing

Standard ANSI Y14.5-1994 GD &T Symbology (descriptive adjectives)

How is the part used? How does it mate to another part?

Rule #1:Where only a tolerance of size is specified, the limits of size of an

individual feature prescribe the extent of which variations in its geometric form,

as well as size, are allowed.ANSI Y14.5 1994

A cylinder can have a variety of shapes yet stay within the limits of size.

(A) (B) (C)Min Min Min

Max Max Max

The rectangular prism can vary in shape as long as it stays inside the volume of the limits of size.

1614

11997

2220

7

8(A) (B)

1816

16.015.8

8.0 MMC

7.8 LMC alongentire lengthof dowel

6.8MMC

7.0LMC

7.06.8

8.07.8

Ring gage

Plug gage

(A) Checking geometric form with ring gage

(B) Checking geometric form with plug gage

A ring gage and plug gage are used to check the geometric form of a pin and hole.

Degrees of freedom allow movement in two directions along each axis and rotation about each axis.

+Y

-X+Z

-Y

+X-Z

Datum features X and Y establish a coplanar datum.

X Y

Simulatedcoplanardatum X-Y

Datum feature X

Datumfeature Y

A) This drawing

B) Means this

.08 X-Y

Two additional examples of feature control frames modifying a parts geometry.

0.08 0.05 A

Geometric tolerance(flatness)

Numeric tolerance

Geometric tolerance(perpendicularity)

Diameter symbolNumeric tolerance

ModifierDatum

(A) (B)

Geometric characteristic symbols are categorized in two ways.

**

Perpendicularity

Angularity

Runout Circular

Runout Total

Profile surface

Profile line

Symmetry

Cylindricity

PositionConcentricity

Circularity

Straightness

Parallelism

Flatness

Either filled or unfilled

Symbol Description

Form

Prof

ileO

rient

atio

nLo

catio

nR

unou

t

Type oftolerance

Individualfeatures

Individual orrelated features

Relatedfeatures

Geometric Characteristic Symbols

*

GD&T geometric characteristic symbols illustrated.

1.5h M1.5h h 0.8h

2h1.5h

0.6h

h

1.5h

Concentricity Circularity Modifier

Straightness Parallelism Flatness

1.5h

Flatness of a surface has a tolerance zone formed by two parallel planes separated by the tolerance value.

Parallel planes 0.3 apart

14.614.0

0.3

(A) This drawing

(B) Means this

14.614.0

The entire area of the part slides over the dial indicator which is poking through the inspection table.

Part being inspectedslides on table

Dial indicatorInspection

table insection

A surface is called out to be flat within 0.2.

0.2

(A) flatness callout

Flatness is checked by leveling the surface with adjustable jacks and inspecting with a dial indicator.

Adjustablejacks

Dial indicatorInspected surface

A specific area is checked for flatness using basic dimensions, callout, and phantom lined hatched area.

820

1218

0.08

Data Analysis LabGD & TGeometric Dimensioning and TolerancingSlide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16