1 dimensioning and tolerancing. 2 prismatic.sldasm

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1 DIMENSIONING AND TOLERANCING

Author: fernando-bachus

Post on 31-Mar-2015

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1 DIMENSIONING AND TOLERANCING Slide 2 2 prismatic.sldasm Slide 3 3 DIFFERENT TYPES OF FIT Clearance fit Limits of size defined such that a clearance always results when mating parts are assembled Interference fit Limits of size are so prescribed that interference always results when mating parts are assembled. Transition fit Limits of size are so prescribed that either clearance or an interference may results when mating parts are assembled Line fit Limits of size are so prescribed that surface contact or clearance may result when mating parts are assembled Slide 4 4 BASIC HOLE SYSTEM In the basic hole system the minimum (lower limit) hole size is taken as the basic size. Stock hole is made first and then shaft is made to particular type of fit (to suit the hole). Slide 5 5 BASIC SHAFT SYSTEM In the basic shaft system the maximum (upper limit) shaft size is taken as the basic size. Stock shaft is created first and hole is made to particular type of fit (to suit the shaft). Slide 6 6 Basic shaft or basic hole? In the basic hole system the minimum (lower limit) hole size is taken as the basic size. Stock hole is made first and then shaft is made to particular type of fit (to suit the hole). In the basic shaft system the maximum (upper limit) shaft size is taken as the basic size. Stock shaft is created first and hole is made to particular type of fit (to suit the shaft). IDENTIFY FIT SYSTEM Slide 7 7 Shaft Hole - - = = What type of fit is this? IDENTIFY FIT SYSTEM Slide 8 8 Slide 9 9 Basic hole More commonly used Basic shaft Less commonly used Slide 10 10 Shown are limit tolerances IDENTIFY FIT SYSTEM Slide 11 11 Surface roughness for different manufacturing methods http://mdmetric.com/pdf/surfruff.pdf Slide 12 12 Slide 13 13 Basic hole fits Slide 14 14 Basic shaft fits Slide 15 15 Description of preferred fits Slide 16 16 ANSI PREFERRED HOLE BASIS METRIC CLEARANCE FITS Pages 312, 313, 314, 315 ANSI PREFERRED SHAFT BASIS METRIC CLEARANCE FITS Pages 316, 317, 318, 319 Engineering Design Graphics James Leake Jacob Borgerson Slide 17 17 cylindrical_metric.sldasm Nominal diameter 25mm Btw. what is wrong with this assembly? Slide 18 18 Loose running fit for nominal diameter 25mm preferred hole basic Slide 19 19 Free running fit for nominal diameter 25mm preferred hole basic Slide 20 20 Close running fit for nominal diameter 25mm preferred hole basic Slide 21 21 Sliding fit for nominal diameter 25mm preferred hole basic Slide 22 22 Locational transition fit for nominal diameter 25mm preferred hole basic Slide 23 23 Locational transition fit for nominal diameter 25mm preferred hole basic Slide 24 24 Locational interference fit for nominal diameter 25mm preferred hole basic Slide 25 25 Medium drive fit for nominal diameter 25mm preferred hole basic Slide 26 26 Force fit for nominal diameter 25mm preferred hole basic Slide 27 27 Hole is always the same: H7 We obtained the desired fit by changing shaft tolerance