International Institute of GD&T
Precision GD&T:
Complimentary slides to Chris Monnier at
Boston Scientific
Dr. Greg Hetland, President
International Institute of GD&T
www.iigdt.com
© IIGDT – GD&T Introduction & Fundamental Principles - May 28, 2006
Plus / Minus Tolerancing
This method of tolerancing allows the axis of the hole to move
plus something and minus something in the X and Y direction.
This creates a square tolerance zone in which the holes must lie?
4X  12.5 + 0.1
25 
0.1
0.1
0.1
50  0.1
© IIGDT – GD&T Introduction & Fundamental Principles - May 28, 2006
Linear Transformation to GD&T
Geometric Dimensioning & Tolerancing (GD&T) creates cylindrical
tolerance zones by removing the tolerance from the dimensions
and applying it to the features. In this example, the geometric
control is position. Dimensions are basic boxed , theoretically
exact, with no tolerance.
4X  12.5 + 0.1

Total Tolerance
25
Diameter Symbol
Position Symbol
50
© IIGDT – GD&T Introduction & Fundamental Principles - May 28, 2006
Feature Control Frame
Geometric Characteristic
Diameter Symbol
Feature Tolerance
Feature Modifier
Projected Tolerance Zone Symbol
Height of Projected Tolerance Zone
Primary Datum
Secondary Datum
Datum Modifier
Tertiary Datum



© IIGDT – GD&T Introduction & Fundamental Principles - May 28, 2006
Profile Comparison to Linear…
Profile
© IIGDT – GD&T Introduction & Fundamental Principles - May 28, 2006
Linear
Tolerancing Consideration #1
























0
0
0

20±0.2
0
0
Only in Diagonals
 
 


20±0.2
 
 


0.26
0.26
0.24
0.24
0.22
0.22
0.2
0.2
0.18
0.18
0.16
0.16
0.14
0.14
0.12
0.12
0.1
0.1
0.08
0.08
0.06
0.06
0.04
0.04
0.02
0.02
0
0
20.24
20.12 20.16
20.2
19.76
19.8
19.84 19.88
19.92 19.96
20.04 20.08
19.78 19.82
19.94 19.98
20.02 20.06
20.18
20.22
19.9
20.1
20
20.14
20.26
19.74
19.86
© IIGDT – GD&T: Advanced Applications & Analysis – June 25, 2006
Virtual Condition
LMC
MMC
MMC
LMC




0


Only in Diagonals
Tolerancing Consideration #5



  










 
 









 








 


















0
0
0

0
0.24
20±0.2
0
 
 
0.26


20±0.2





0.26
0.24
0.22
0.22
0.2
0.2
0.18
0.18
0.16
0.16
0.14
0.14
0.12
0.12
0.1
0.1
0.08
0.08
0.06
0.06
0.04
0.04
0.02
0.02
0
0
20.24
20.12 20.16
20.2
19.76
19.8
19.84 19.88
19.92 19.96
20.04 20.08
19.78 19.82
19.94 19.98
20.02 20.06
20.18
20.22
19.9
20.1
20
20.14
20.26
19.74
19.86
© IIGDT – GD&T: Advanced Applications & Analysis – June 25, 2006
Virtual Condition
LMC
MMC
MMC
LMC



0


GD&T
Boundary
Comparisons
Form
Straightness

Flatness

Circularity
Cylindricity
Profile
Orientation
Angularity

Perpendicularity

Parallelism

Location
Position


Concentricity


Symmetry

Runout
Profile of a
Surface

Circular Runout

Profile of a
Line

Total Runout

© IIGDT – GD&T: Advanced Applications & Analysis – June 25, 2006
Global Simplification of GD&T
3D Surface
Control

Profile of a
Surface
2D Surface
Control

Profile of a
Line
Axis Control

Position
© IIGDT – GD&T: Advanced Applications & Analysis – June 25, 2006

Angularity

Perpendicularity
Parallelism

Cylindricity

Total Runout 
Concentricity 
Symmetry

Straightness 
Circularity

Circular Runout 
Straightness 

Angularity
Perpendicularity
Parallelism

Concentricity

Symmetry

Flatness
GD&T Fonts ($49 each)
available by
calling IIGDT at 952-936-9499
or
sending and E-mail to:
iigdt@bcmn.com
© IIGDT – GD&T: Advanced Applications & Analysis – June 25, 2006