1. Geometric Dimensioning and Tolerancing Course Number Instructor’s name Planchard Copyright 2012

2. What is Geometric Dimensioning and Tolerancing “GDT” It is a system of symbols, rules and definitions used to define the shape (Roundness, Flatness, Cylindricity, etc.) and design Intent (parallel, perpedicular, concentric, et.) of the model. Planchard Copyright 2012

3. Objectives of GDT Define parts based on function Include geometric as well as size tolerances Facilitate inspection and quality control Reduce need for notes Capture design intent Clarify tolerances for international use Eliminate tolerance stack-up Planchard Copyright 2012

4. Objectives of GDT Orthogonal Datum Planes “3-2-1” Rule 3 points of contact 1 point of contact A rule that defines the minimum number of contact points necessary to properly locate a part within the datum reference frame. The primary datum requires three points, the secondary datum two points, and the tertiary datum one point. 2 points of contact Planchard Copyright 2012

5. Simple Part with GDT Dimension tolerance does not say anything about the shape of the part! GDT controls the shape and the initial design intent. Tolerance of the feature Design Intent Roundness symbol of the feature Primary datum Secondary datum Tolerance of the dimension Design Intent Perpendicularity symbol of feature Planchard Copyright 2012

6. Simple Part with GDT Tertiary datum Secondary datum Primary datum Flatness symbol of the feature Perpendicularity symbol of the feature Position symbol of the feature: Hole Dimension tolerance does not say anything about the shape of the part! GDT controls the shape and the initial design intent. Tolerance of the dimension Tolerance of the datum feature Planchard Copyright 2012

7. Simple Part with GDT Roundness: (ASME Y14.5M 1994 Section 2.7.1.3, paragraph (a)). Circular runout Secondary Datum plane Primary Datum plane Cylindrical face Tolerance of the datum featured Tolerance of the dimension Planchard Copyright 2012

8. Simple Part with GDT Roundness: (ASME Y14.5M 1994 Section 2.7.1.3, paragraph (a)) Planchard Copyright 2012

9. Simple Part with GDT Yes No Perpendicularity symbol of the feature Perpendicularity symbol of the feature Flatness symbol of the feature Primary Datum plane Planchard Copyright 2012

10. Simple Part with GDT Angularity symbol of the feature View the selected Datum planes, the angularity symbol was added afterwards! Perpendicularity symbol of the feature Planchard Copyright 2012

11. Simple Part with GDT Note: The different Datum planes selected to display the Angularity symbol of the feature from the previous slide! Angularity symbol of the feature Flatness symbol of the feature Perpendicularity symbol of the feature Planchard Copyright 2012

12. Simple Part with GDT Dimension tolerance does not say anything about the shape of the part! GDT controls the shape and the initial design intent Datum C is the face of the feature: Simple Hole Position symbol of the feature Flatness symbol of the feature Offset, arrows will not fit. Planchard Copyright 2012

13. Simple Part with GDT Dimension tolerance does not say anything about the shape of the part! GDT controls the shape and the initial design intent Position symbol of the feature Flatness symbol of the feature Planchard Copyright 2012

14. Simple Part with GDT Parts Do Not Have Center Lines—Features Have Axes Center lines are a drafting convenience. Associate the datum feature symbol with datum features! Total runout symbol of the feature No “For Construction” Centerline! Planchard Copyright 2012

15. Simple Part with GDT Coaxial Diameters - Two (or more) diameters that are shown on the drawing as being on the same centerline (axis). Revolved Base Feature : Axis of revolutions Vs. Extruded Base Feature. Circular runout symbol of the feature Circular runout symbol of the feature Planchard Copyright 2012

16. Simple Part with GDT Profile of a Surface symbol of the feature Tertiary Datum Primary Datum Secondary Datum Planchard Copyright 2012

17. GDT Symbols http://www.wisc-online.com/objects/index_tj.asp?objID=ENG18804 Planchard Copyright 2012

18. Default Document Datum Tolerances (DimXpert) Planchard Copyright 2012

19. Material Condition Symbols Maximum Material Condition (MMC) –largest shaft, smallest hole Least Material Condition (LMC) –smallest shaft, largest hole Regardless of Feature Size (RFS) MLS Planchard Copyright 2012

20. Tolerance Zones without GDT Means this! The tolerance area or boundary with that forms the Feature may vary when no tolerance of the feature is provided Planchard Copyright 2012

21. GDT Rule 1 Individual Feature of Size –Where only a tolerance of size is specified, the limits of an individual feature prescribe the extent to which variations in its geometric form, as well as size, are allowed. Planchard Copyright 2012

22. Location Controls Position Concentricity Runout Planchard Copyright 2012

23. GD&T True Positioning Note circular tolerance zones Planchard Copyright 2012

24. Straightness Planchard Copyright 2012

25. Flatness The surface must be within the tolerance of size and must lie between two parallel planes: 0.25 apart (feature tolerance) Symbol Tolerance of the feature Planchard Copyright 2012

26. Roundness Each circular element of the Surface in any plane perpendicular to A common axis must be within the specified tolerance of size. It also must lie between two concentric circles – one having a radius of 0.25 larger than the other! Symbol Tolerance of the feature Planchard Copyright 2012

27. Cylindricity The cylindrical surface must be within the specified tolerance of size, in this example 0.25 and must lie between two Concentric cylinders – one having a radius of 0.25 larger than the other. Symbol Tolerance of the feature Planchard Copyright 2012

28. Orientation Controls Perpendicularity Parallelism Angularity Line Profile Surface Profile Planchard Copyright 2012

29. Parallelism for Planes The surface must be within the specified Tolerance (0.12) of size and must lie between two planes (0.12) apart which are parallel to Datum Plane A. Symbol Tolerance of feature Datum Plane Planchard Copyright 2012

30. Parallelism for Axis and Plane The feature axis must be within the specified tolerance (0.12) of location and must lie between two planes (0.12) apart which are parallel to the datum plane (A) regardless of the feature size! Planchard Copyright 2012

31. Parallelism for Two Axes The feature axis must be within the specified tolerance (0.05) of location. Where the feature is at Maximum Material Condition (10.00). The Maximum Parallelism tolerance is (0.05). Planchard Copyright 2012

32. Perpendicularity of Axis vs. Plane The feature axis must be within the specified tolerance(0.05) of location. Where the feature is at MMC (15.984) the Max perpendicularity tolerance is 0.05. Where the feature departs from it’s MMC size, and increase in the Perpendicularity tolerance is ALLOWED which is equal to the amount of the departure. Planchard Copyright 2012

33. All parts are not created equal! Profile of a line is a funny control. It works well for parts like extrusions where individual slices will be checked. However, when you start adding datum references, it can turn into a profile of a surface control CNC issues! Planchard Copyright 2012