GD&T Fundamentals with Stack and Gaging Applications

Introduction

• Welcome to Geometric Dimensioning & Tolerancing
• The 12 Geometric Controls Exercise: —Students draw the symbols, names, and feature control frame examples and complete a list of tolerance zone modifiers. 
• Exercise debrief: Overview of everything/job aid. 
• GD&T Tool Categories vs. Geometric Attributes: Use a matrix to avoid confusion!

Features of Size vs. Surfaces (Big Map of the GD&T World)

• What is a feature, exactly? 
• What’s the difference between a surface and a feature of size?
• Organizing features of size: 
• What’s “Rule #1”? Size controls form, too.
• Does ISO have a Rule #1 and is it different than ASME’s? ISO has a Rule #1 that says form is independent of size.
• Exercises & debrief 

Controlling Surface Form

• Flatness & Straightness 
• Cylindricity & Roundness 
• Profile as a Form Control 
• Exercises (Homework)
• Surface form exercise debrief

Datums

• What are they? Theoretical planes, lines, or points used as origins for locating and orienting other features.
• Why do we need them? —You can’t locate or orient two related features to each other without designating one of them as the origin and then controlling the other feature in relation to the first.
• Get the definitions right: datums, datum features, fixtures, and gages 
• Surfaces used as datums
• Features of size used as datums: To M or not to M, that is the question Sometimes you’re OK when shift happens. 
• Patterns of features used as a datum 
• Exercises and applications 
• How do you select a datum? First follow the function.
• How do you simulate a datum? Match the way you reference it and simulate it to the way it functions. 
• More exercises & debrief 

Controlling Surface Orientation

• Perpendicularity 
• Angularity & Parallelism 
• What’s the tangent plane modifier for? Changing what, exactly, has to be in the tolerance zone. 
• Exercises & debrief 

Orienting a feature of size 

• Definition 
• To M or not to M, that is the question. If a feature’s size varies in a way that helps the fit, can you count that size variation as additional geometric tolerance? 
• Round and square examples 
• Inspection 

Using FOS and Surfaces controlled with profile as datums

• MMB: Shift happens
• RMB: No shift
• [BSC] and LMB
• Patterns of features used as a datum
• Datum targets
• Datum translation
• Custom degrees of freedom  [x, y, z, u, v, w]
• Exercises and applications
• Debrief

Location

• Position
• Runout
• Concentricity & Symmetry-Legacy controls. How to get along without them?

Verifying GD&T

• Stacking up tolerances: Developing skill takes solving some problems!
• Max/Min Stacks
• Assembly Stacks
• Stacking Location-Related Controls
• Stacking Profile Tolerances
• Stacking Position with Modifiers 

Using ASME Y14.43-2011 Dimensioning and Tolerancing Principles of Gages and Fixtures Standard

• Gaging goals, approaches, and recommendations: What gaging philosophy should you follow.
• How should I tolerance the gage?

Course Close 

• Review 
• Posttest 
• Other resources 
• ASME Certification info