Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 1 Dimensioning & Tolerancing

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 2 Dimensioning Size dimensions 2D drawings (shop drawings) must show proper dimensions to fabricate parts Location and orientation dimensions

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 3 Dimensioning Terminology 1.25 Numerical value that defines the size and location Dimension line Extension line Gap Extension line offset

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 4 Pull down menu Dimension Style

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 5

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 6 Accuracy 1.25 indicates ±.01 variation is acceptable (1.24 to 1.26) Requires twice as much time to machine. Use fractional dimensions when accuracy is not important, 2 ¼, 5 ½,….. Architectural dimensioning: use combination of feet and inches, 7’ – indicates ±.01 variation is acceptable, or ±.001 variation is acceptable (1.249 to 1.251) NOT

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 7 Placement of Dimensions

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 8 Do’s & Don’t’s of Dimensioning Never dimension hidden lines

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 9 Do’s & Don’t’s of Dimensioning

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 10 Dimensioning

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 11 Avoid Over-Dimensioning

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 12 Avoid Over-Dimensioning Θ = tan -1 (12.7/7.1) = 60.8 o

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 13 Basic Dimensioning Style Continue dimensioning Baseline dimensioning Ordinate dimensioning

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 14 Tolerancing Parts made by different companies have to be interchangeable. Mating parts have to fit precisely. Tolerancing is the technique of dimensioning parts within a desired range of variation. Why tolerancing?

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 15 Size Tolerancing Limit Form Bilateral ±.003 _ Unilateral

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 16 Mating Parts

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 17 Type of Fits for Mating Parts Clearance Fit – Results in a space between the mating parts. Interference Fit – Results in an interference between two parts (no space). It requires force to assemble parts (force fit). Transition Fit – May results in either interference or clearance fit.

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 18 Example – Clearance Fit

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 19 ANSI Tables for Fits Clearance fits (running and sliding) – RC1 to RC Class RC 4

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 20 ANSI Tables for Fits Clearance fits (Locational) – LC1 to LC11

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 21 ANSI Tables for Fits Interference fits (Force and Shrink fits) – FN1 to FN

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 22 Geometric Tolerancing Geometric Dimensioning and Tolerancing (GDT) GDT defines the features of a part more efficiently than just the size. It also defines the standards for verifying the specified size and form. ANSI Y

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 23 Geometric Tolerancing Geometric tolerancing is a system that specifies the form, profile, orientation, and location of part’s features using the ANSI standards.

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 24 Geometric Tolerancing - Examples Form tolerancing Flatness Straightness Profile tolerancing Line

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 25 Geometric Tolerancing - Examples Orientation tolerancing Perpendicularity Parallelism Angularity

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 26 Geometric Tolerancing - Examples Location tolerancing Concentricity Symmetry

Ken YoussefiMechanical & Aerospace Engineering Dept., SJSU 27 Exam 1 – Friday Oct. 6, 9-10 (E-341) Type of problems 2.3D views - given the three standard views, draw an oblique or isometric views. 1.2D views - given an isometric view of an object, draw the three standard views (front, top and right side). 3.Missing line problems - given standard views of an object with some features missing, draw the missing features. All views are drawn freehand, no straight edge. Bring soft pencil and eraser, paper will be provided. 4.Section views – definition and standards. 5.Dimensioning standards and conventions. 6.3D visualization.