GD&T

SESSION - 1

BASICS OF GD&T

AGENDA

1. Why GD&T

2. DATUM & PRINCIPLE OF DATUM

3. TERMINOLOGIES

4. TYPES OF TOLERANCING

5. FEATURE CONTROL FRAME

6. GD&T VS CO-ORDINATE DIMENSIONING

7. GD&T SYMBOLS

8. FORM TOLERANCE

9. EXCERSISE

Why GD&T

GD&T

FunctionUniform

Interpretation

DATUM & PRINCIPLE OF DATUM (3-2-1 Principle)

TERMINOLOGIES

What is MMC – Maximum Material Condition ?

What is LMC – Least Material Condition?

What is RFS – Regardless of Feature Size?

What is Bonus Tolerance?

What is Feature of Size?

What is Virtual Condition?

TYPE OF TOLERANCE

TYPES OF TOLERANCE

Exercise

1. What is MMC and LMC of the feature mentioned below?

30+0-0.5A

ø5±.5

B

C2±.5

GD&T FEATURE CONTROL FRAME

Geometric Tolerance Vs Co-ordinate Tolerance

A Dimension system where a part feature is located (or defined) by means of rectangular dimensions with given tolerances.

It is an international language used on engineering drawings to accurately describe a part. A dimensioning philosophy that defines a part based upon how it functions in final product

10±0.5

10±0.5

9.5 10 10.5

10.5

9.5

9.5 10 10.5

10.5

9.5Position Tolerance of ø1.0

10

10

1.0

GD&T SYMBOLS

FORM TOLERANES

1. Never uses datum for reference.

2. The form tolerance will be less than the dimensional tolerance.

3. Bonus tolerance applicable when applied to FOS

STRAIGHTNESS

• Straightness Tolerances Never use a datum for reference.

• Modifiers M applicable when flatness applied to FOS

STRAIGHTNESS

Straightness applied to planar surfaces

Inspection of straightness applied to planar surfaces

STRAIGHTNESS

Inspected at Virtual Condition

• Straightness applied to FOS

• Bonus Tolerance applicable

FLATNESS

• Flatness Tolerances Never use a datum for reference.

FLATNESS

Flatness applied to planar surfaces

Inspection of Flatness applied to planar surfaces

CIRCULARITY

• Circularity Tolerances Never use a datum for reference.

CIRCULARITY

Circularity applied to cylindrical surfaces

Inspection of circularity applied to cylindrical surface

.004 larger than the other

CYLINDRICTY

• Circularity Tolerances Never use a datum for reference.

CYLINDRICITY

Cylindricity applied to cylindrical surfaces

Exercise - 1

.002 A

Is this representation Correct?

Exercise - 2

.002

Is this representation Correct?

Ø 25.0/24.0

Exercise - 3

Represent all the form tolerances where applicable

.002

.002

Exercise - 4

Is this Correct?

0.5

Ø 25.0+0.2

0

Exercise - 5

1. Is this representation Correct?

2. What is the Bonus tolerance at MMC?

3. What is the Bonus tolerance at LMC?

+0.1

05.00

M .05

SESSION - 2

LOCATION TOLERANCES

LOCATION TOLERANCES

POSITION TOLERANCE

EXAMPLE - 1

POSITION TOLERANCE

EXAMPLE - 2

LOCATION TOLERANCES

EXAMPLE - 3

Exercise - 1

-A-

-B- -C-

1. What is the position tolerance available?

2. What is the Tolerance Zone?

3. What is the maximum position of the hole axis?

4. Is Bonus tolerance applicable in this case?

5. If Bonus tolerance to be applicable what shall be done to the representation?

Exercise - 2

EXAMPLE - 2

-A-

-B- -C-

1. If the function of the mating part is just for guiding into the hole….What is the position tolerance and the dimension on the mating part?

2. What is the maximum clearance available between features after assembly of the 2 parts in worst Case condition?

Exercise 3

EXAMPLE - 3

Produce mating components for the drawings. Assemble, Assume dimensions, tolerance and fits based on functions.