1

GD&T 4Tolerance Zones

.010 M P 1.25 C D E

2X .500 13 UNC – 2B

CAD/Fab GD&T 4 - Tolerance zones 2

Tolerance Zones

• Circular– Specified by diameter symbol -

• Non-circular– Bounded by parallel lines or planes

3

GD&T Summary Chart (see web site)

CAD/Fab GD&T 4 - Tolerance zones 4

Flatness Lab - Drawing

Tolerance zone = two parallel planes 4 mm apart

CAD/Fab GD&T 4 - Tolerance zones

2

GD&T Summary Chart (see web site)

5

RFS = Regardless of Feature Size

CAD/Fab GD&T 4 - Tolerance zones 6

Flatness Lab - Interpretation

4 mm

• All parts of surface must lie between parallel planes • Planes may be any orientation relative to part• They are not associated with any datums

CAD/Fab GD&T 4 - Tolerance zones

7

Lego Lab - Drawing

CAD/Fab GD&T 4 - Tolerance zones 8

GD&T Summary Chart (see web site)GD&T Summary Chart (see web site)

CAD/Fab GD&T 4 - Tolerance zones

3

9

Tolerance zone Perpendicular to datum plane A

Tolerance zonewidth

Lego Lab - Interpretation

CAD/Fab GD&T 4 - Tolerance zones 10

Rule of Thumb

• GD&T tolerance values are typically less than half the size limits.

Size limits

GD&T toleranceCAD/Fab GD&T 4 - Tolerance zones

11

Perpendicularity of Axis

Circular tolerance zone

.05

CAD/Fab GD&T 4 - Tolerance zones

Circular Runout Lab - Drawing

CAD/Fab GD&T 4 - Tolerance zones 12

4

CAD/Fab GD&T 4 - Tolerance zones 1313

GD&T Summary Chart (see web site)GD&T Summary Chart (see web site) Circular Runout Lab - Testing

CAD/Fab GD&T 4 - Tolerance zones 14

1. Clamp part on center hole (datum A)2. Rotate about axis and measure runout with dial indicator

Tolerance zone =Area between 2 circles

Runout of Non-Cylindrical Parts

CAD/Fab GD&T 4 - Tolerance zones 15

The tolerance zone is a pair of perfect circles, the tolerance value apart, and perfectly centered on the datum axis. But the diameters of the circles may vary as you move along the part.

Verifying FormGages are used to measure variation - e.g. “runout”

Motion of tip is displayed to 0.001” precision

Dial indicator16CAD/Fab GD&T 2 - Datums

5

Snowboard Binding - Drawing

CAD/Fab GD&T 4 - Tolerance zones 17 CAD/Fab GD&T 4 - Tolerance zones 18

GD&T Summary Chart (see web site)

CAD/Fab GD&T 4 - Tolerance zones 19

Snowboard Binding - Testing

Datum Feature ASmooth surface locates part flat

Datum Feature BThree jaws move in and out together to center cylindrical feature

Datum Feature CWedge centers part on notch

CAD/Fab GD&T 4 - Tolerance zones 20

Snowboard Binding - Testing

6

CAD/Fab GD&T 4 - Tolerance zones 21

Snowboard Binding - Testing

Tolerance zones for location of hole axes are cylindricalThey are perfectly perpendicular to datum A,and they are located exactly by the basic dimensions