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Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian Institute of Technology, Bombay

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Page 1: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Geometric Dimensioning and Tolerancing

1

Prof. S. S. Pande

Mechanical Engineering Department

Indian Institute of Technology, Bombay

Page 2: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Outline

• Importance of Geometric Dimensioning & Tolerancing

• Tolerance Symbols

• Tolerance Specification and Interpretation • Form, Orientation, Location,

Position, Runout

Page 3: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

• International standard to specify Form, Fit and Function of parts

• ANSI Y 14.5, ISO 1101

• Significant improvement over traditional tolerancing

• Focuses on 3D part geometry features in addition to 2D drawings

What is GD & T ?

Page 4: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

A Typical Part Drawing

Page 5: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

When to use GD & T ?

• Part features are critical to function or interchangeability

• Datum references are desirable

• Functional gaging techniques are preferred

• Standard interpretation of tolerance is not implied

Page 6: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Why to use GD & T ?

• Ensures Specification of Design Tolerance requirements

• Ensures interchangeability of parts during assembly

• Provides standardization and uniformity • Adaptation to 3D CAD modeling

• Leads to high productivity, less rework and reduced cost.

Page 7: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Part Geometry Features to be controlled

• Form

• Orientation

• Location

• Position

• Runout

Page 8: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Geometric Tolerance Symbols

Page 9: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Tolerance Feature Frame

Page 10: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Part Datums

Page 11: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Part Datum for Inspection

Page 12: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Datum Planes

Page 13: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Datum Planes and Axis

Page 14: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

3 – 2 - 1 Part Datum Location

Page 15: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Form Tolerances

• Control the form with reference to Ideal shape

• Applies to Line, Arc, Circle, Profile, Surface

• Tolerance is a Peak- to – Valley measure

Page 16: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Types of Form Tolerances

Straightness

Flatness

Roundness

Cylindricity

Profile of line

Profile of Surface

Page 17: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Straightness Tolerance

Page 18: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Straightness Tolerance – Line / Axis

On the Drawing Interpretation

Page 19: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Flatness Tolerance

Page 20: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Flatness Tolerance – Plane

On the Drawing Interpretation

Page 21: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Circularity (Roundness) Tolerance

Page 22: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Circularity (Roundness) Tolerance

On the Drawing

Interpretation

Page 23: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Cylindricity Tolerance

On the Drawing Interpretation

Page 24: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Orientation Tolerance

• Specifies relative orientation (Attitude) between entities

• Edges, Axes, Surfaces, Features

• Always need a Datum (Reference) Plane / Feature.

Page 25: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Types of Orientation Tolerances

Parallelism

Perpendicularity

Angularity

Page 26: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Parallelism Tolerance

On the Drawing Interpretation

Page 27: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Parallelism Tolerance - Planes

Page 28: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Parallelism Tolerance - Features

On the Drawing Interpretation

Page 29: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Parallelism Tolerance - Features

On the Drawing Interpretation

Page 30: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Perpendicularity Tolerance

On the Drawing Interpretation

Page 31: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Perpendicularity Tolerance

Page 32: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Location Tolerance

• Specifies relative Location (Attitude) between entities

• Edges, Axes, Surfaces, Features

• Always need a Datum (Reference) Plane / Feature.

Page 33: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Concentricity Tolerance

Page 34: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Material Condition Modifiers

Maximum Material Condition (MMC)

• Largest (size) shaft • Smallest (size) Hole

Symbol : M

Regardless of Feature size (RFS)

Page 35: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

MMC – RFS Condition

ANSI/ ISO recommends

• Form of a feature is Perfect (Ideal) at MMC

• If not specified, treat Feature Tolerance as RFS.

Page 36: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Position Tolerance

• Controls Position (Centre or Axis) of Holes

• Needs Datums

• Primary/ Secondary/ Tertiary

• Tolerance Zone

• Circular

• Rectangular

Page 37: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Position Tolerance

Page 38: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Run Out Tolerance

• Primarily for cylindrical rotating parts

• Types of Run Out

• Circular Run Out • Total Run Out

Page 39: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Run Out Tolerance

Circular Total

Page 40: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Functional Gaging

• To test the combined effect of All tolerances

• Dimensional Tolerance • Geometric Tolerance

• Gage - Extreme Virtual Size

Page 41: Geometric Dimensioning and Tolerancing - IIT Bombayramesh/courses/ME338/ssp1.pdf · Geometric Dimensioning and Tolerancing 1 Prof. S. S. Pande Mechanical Engineering Department Indian

Gage - Extreme Virtual Size