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DIMENSIONING AND TOLERANCING
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prismatic.sldasm
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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
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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).
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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).
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IDENTIFY FIT SYSTEM 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).
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IDENTIFY FIT SYSTEM “Shaft” “Hole” - = - = What type of fit is this?
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IDENTIFY FIT SYSTEM
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IDENTIFY FIT SYSTEM Basic hole More commonly used Basic shaft
Less commonly used
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Shown are limit tolerances
IDENTIFY FIT SYSTEM Shown are limit tolerances
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Surface roughness for different manufacturing methods
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Φ Basic hole fits
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Φ Basic shaft fits
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Description of preferred fits
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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
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cylindrical_metric.sldasm
Nominal diameter 25mm Btw. what is wrong with this assembly? cylindrical_metric.sldasm
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Loose running fit for nominal diameter 25mm preferred hole basic
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Free running fit for nominal diameter 25mm preferred hole basic
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Close running fit for nominal diameter 25mm preferred hole basic
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Sliding fit for nominal diameter 25mm preferred hole basic
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Locational transition fit for nominal diameter 25mm preferred hole basic
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Locational transition fit for nominal diameter 25mm preferred hole basic
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Locational interference fit for nominal diameter 25mm preferred hole basic
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Medium drive fit for nominal diameter 25mm preferred hole basic
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Force fit for nominal diameter 25mm preferred hole basic
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Hole is always the same: H7
We obtained the desired fit by changing shaft tolerance
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