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.