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Introduction to Engineering Tolerancing - 2

Introduction to Engineering Tolerancing - 2. Agenda Determining limits Use standard tables for tolerancing and control fit. How to Determine Limits. Now you can calculate tolerances, given the max and min limits on a dimension How does a design engineer know what limits to use?

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Introduction to Engineering Tolerancing - 2

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  1. Introduction to EngineeringTolerancing - 2 Agenda Determining limits Use standard tables for tolerancing and control fit

  2. How to Determine Limits • Now you can calculate tolerances, given the max and min limits on a dimension • How does a design engineer know what limits to use? • First, decide what type of fit you want. • Then, use a table.

  3. Standard Precision Fits: English Units • Running and sliding fits (SC) • Clearance locational fits (LC) • Transition locational fits (LT) • Interference locational fits (LN) • Force and shrink fits (FN) See Tables in the Appendix

  4. Example – What are tolerance limits for a Nominal ½” shaft with RC2 fit? Hole Max .5004 Min .5000 Shaft Max .49975 Min .49945

  5. Metric Limits and Fits • Based on Standard Basic Sizes – ISO Standard, see Appendix material • Nominal Size = Basic Size • Symbols and Their Definitions

  6. Metric Preferred Hole Basis System of Fits

  7. 5.990 5.978 6.018 6.000 Metric Tolerance Example - Nominal 6 mm Hole and Shaft with Close Running Fit 6 H8/f7 Shaft Hole

  8. Fill1 Fill2 Clearance Gap Basic System Clearance = Gap – Fill Fill = Fill1 + Fill2 • Cmax = Gmax – Fmin • Cmin = Gmin – Fmax Both Cmax and Cmin >0 – Clearance fit Both Cmax and Cmin <0 – Interference fit Cmax > 0 Cmin < 0 – Transition fit • System Tolerance = Cmax - Cmin

  9. .505 .500 .755 .750 Clearance 1.248 1.240 Gap and Fill Clearance Example Clearance = Gap – Fill Cmax = Gmax – Fmin Cmax = 1.248 - .500 - .750 = -.002 Cmin = Cmin = What is Type of Fit?

  10. Assignment Dwg 8: Tolerance and Fits Worksheet

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