Geometrical Dimensioning & Tolerancing

ISO 1101

By Hassan Habib

What are we going to learn

What is Geometrical Dimensioning & Tolerancing

Its :

benefits

Types

Some general principles

Details of tolerances of:

Form

Orientation

Location

Profile

What is Geometrical Dimensioning

Tolerancing

Hmmmm. . . . What would I

prefer?

Slide Title

Benefits of

GD&T

Geometrical tolerances vs size tolerances

Precision & Accuracy

Reduced rework cost

Reduced Defects

Increased understanding

Mfg Design Quality

Slide Title

Types of

GD&T

Types of Geometrical tolerances

Form Tolerances

Orientation Tolerances

Location tolerances

runout tolerances

• Straightness

• Flatness

• Circularity

• Cylindricity

• Parallelism

• Perpendicularity

• Angularity

• Position

• Symmetry

• Concentricity

• Coaxiality

• Circular runout • Total runout

Slide Title

Some general

principles

Some general priciples

Basic concepts

Geometrical tolerances shall be specified in accordance with functional

requirements. Manufacturing and inspection requirements can also

influence geometrical tolerancing

Some general priciples

Basic concepts

Geometrical tolerances which are assigned to features related to a datum

do not limit the form deviations of the datum feature itself. It may be

necessary to specify tolerances of form for the datum feature(s)

Some general priciples

Basic concepts

Feature control frame

Some general priciples

Three golden rules

1. Location tolerances of a feature control location deviation, orientation deviation and form deviation of

this feature, and not vice-versa.

2. Orientation tolerances of a feature control orientation and form deviations of this feature and not

vice-versa.

3. Form tolerances of a feature control only form deviations of this feature.re control frame

Slide Title

Details of

Tolerances

Form Tolerances

straightness

The tolerance zone, in the considered plane, is limited by two parallel

straight lines a distance apart and in the specified direction only

Straightness tolerance

straightness

Any extracted (actual) generating line on the cylindrical surface shall be

contained between two parallel planes T distance apart

Straightness tolerance

straightness

The extracted (actual) median line of the cylinder to which the tolerance

applies shall be contained within a cylindrical zone of diameter

Straightness tolerance

fLATNESS

The extracted (actual) surface shall be contained between two parallel

planes DISTANCE T apart.

flatness tolerance

roundness

The tolerance zone, in the considered cross-section, is limited by two

concentric circles with a difference in radii of t

roundness tolerance

CYLINDRICITY

The tolerance zone is limited by two coaxial cylinders with a difference in

radii of T

cylindricity tolerance

Slide Title

Details of

Tolerances

orientation Tolerances

PARALLELISM

The tolerance zone is limited by two parallel planes a distance apart. The

planes are parallel to the datums and in the direction specified

Direction specified

Parallelism tolerance of a line related to a datum system

PARALLELISM

The tolerance zone is limited by two parallel planes a distance apart. The

planes are parallel to the datums and in the direction specified

Direction specified

Parallelism tolerance of a line related to a datum system

PARALLELISM

The tolerance zone is limited by a cylinder of diameter t , parallel to the

datum, if the tolerance value is preceded by the symbol Ø

Parallelism tolerance of a line related to a datum line

PARALLELISM

Each extracted (actual) line shall be contained between two parallel lines

0,02 apart parallel to datum A and lying in a plane parallel to datum B

Parallelism tolerance of a line related to a datum system

prependicularity

The tolerance zone is limited by two parallel planes a distance apart and

perpendicular to the datum

Perpendicularity tolerance of a line related to a datum line

prependicularity

The tolerance zone is limited by two parallel planes a distance t apart.

The planes are perpendicular to the datum A and parallel to datum B

Perpendicularity tolerance of a line related to a datum system

prependicularity

The tolerance zone is limited by a cylinder of diameter perpen dicular to

the datum if the tolerance value is preceded by the symbol Ø

Perpendicularity tolerance of a line related to a datum surface

Angularity

a) Line and datum line in the same plane:

The tolerance zone is limited by two parallel planes a distance t apart

and inclined at the specified angle to the datum.

Angularity tolerance of a line related to a datum line

Angularity

b) The tolerance zone is limited by two parallel planes a distance t apart

and inclined at the specified angle to the datum. The considered line and

the datum line are not in the same plane

Angularity tolerance of a line related to a datum line

Angularity

The tolerance zone is limited by two parallel planes a distance t apart and

inclined at the specified angle to the datum

Angularity tolerance of a line related to a datum surface

Angularity

The tolerance zone is limited by a cylinder of diameter t if the tolerance

value is preceded by the symbol Ø. The cylindrical tolerance zone is

parallel to a datum plane B and inclined at the specified angle to the datum

plane A

Angularity tolerance of a line related to a datum surface

Slide Title

Details of

Tolerances

location Tolerances

position

The tolerance zone is limited by a sphere of diameter t if the tolerance

value is preceded by the symbol SØ. The center of the spherical tolerance

zone is fixed by theoretically exact dimensions with respect to the datums

A, B and C

Position tolerance of a point

position

The tolerance zone is limited by two parallel planes a distance t apart and

symmetrically disposed about the center line. The center line is fixed by

theoretically exact dimensions with respect to datums A and B. The

tolerance is specified in one direction only.

Position tolerance of a line

position

The tolerance zone is limited by two pairs of parallel planes a distance 0,05

and 0,2 apart respectively and symmetrically disposed about the

theoretically exact position. The theoretically exact position is fixed by

theoretically exact dimensions with respect to the datums C, A and B. The

tolerance is specified in two directions with respect to the datums.

Position tolerance of a line

position

Position tolerance of a line

position

The tolerance zone is limited by a cylinder of diameter t if the tolerance

value is preceded by the symbol Ø. The axis of the tolerance cylinder is

fixed by theoretically exact dimensions with respect to the datum s C, A

and B

Position tolerance of a line

position

The tolerance zone is limited by two parallel planes a distance t apart and

symmetrically disposed about the theoretically exact position fixed by

theoretically exact dimensions with respect to the datums A and B

Position tolerance of a flat surface or a median p lane

Concentricity

The tolerance zone is limited by a circle of diameter t; the tolerance value

shall be preceded by the symbol . The center of the circular tolerance

zone coincides with the datum point

Concentricity tolerance of a point

coaxiality

The tolerance zone is limited by a cylinder of diameter t; the tolerance

value shall be preceded by the symbol Ø . The axis of the cylindrical

tolerance zone coincides with the datum

Coaxiality tolerance of an axis

symmetry

The tolerance zone is limited by two parallel planes a distance t apart,

symmetrically disposed about the median plane, with respect to the datum.

Symmetry tolerance of a median plane

Slide Title

Details of

Tolerances

Runout Tolerances

Circular runout

The tolerance zone is limited within any cross-section perpendicular to

the datum axis by two concentric circles with a difference in radii of t,

the centers of which coincides with the datum

Circular run-out tolerance —radial

Circular runout

Run-out usually applies to complete features, but could be applied to a

restricted part of a feature

Circular run-out tolerance —radial

Circular runout

The tolerance zone is limited to any cylindrical section by two circles

with a distance t apart lying in the cylindrical section, the axis of which

coincides with the datum

Circular run-out tolerance — axial

Circular runout

Circular The tolerance zone is limited within any conical section b y two

circles a distance t apart, the axes of which coincide with the datum.

Circular run-out tolerance in any direction

Circular runout

The tolerance zone is limited within any conical section of the specified

angle by two circles a distance t apart, the axes of which coincide with

the datum

Circular run-out tolerance in a specified direction

Total runout

The tolerance zone is limited by two coaxial cylinders with a difference in

radii of t, the axes of which coincide with the datum

Total radial run-out tolerance

Total runout

The tolerance zone is limited by two parallel planes a distance t apart and

perpendicular to the datum

Total axial run-out tolerance