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EML 2023 Clearance Fits Lecture 2 Clearance Fits Slide 2 EML 2023 Computer Aided Design Cylindrical Fits 2 Slide 3 EML 2023 Computer Aided Design Cylindrical Fits English Units 3 Slide 4 EML 2023 Computer Aided Design Cylindrical Fits English Units 4 Slide 5 EML 2023 Computer Aided Design Cylindrical Fits English Units 5 Slide 6 EML 2023 Computer Aided Design Cylindrical Fits English Units 6 Slide 7 EML 2023 Computer Aided Design Cylindrical Fits English Units tolerance - difference between the limits of size for a single feature ; shaft.0025 ; hole.0040 limits of tolerance the max and min sizes of a single feature allowance the tightest fit between two mating parts ;.0050 nominal size the general size of a shaft or hole ; 1.5 basic size the size to which the plus-and minus is applied actual size the measured size of the finished part fit - the degree of tightness or looseness between two assembled parts 7 Slide 8 EML 2023 Computer Aided Design Cylindrical Fits English Units clearance fit gives a clearance between two assembled mated parts ; min clearance.005 ; max clearance.0115 transition fit interference fit line fit 8 Slide 9 EML 2023 Computer Aided Design Cylindrical Fits English Units clearance fit interference fit a binding fit that requires the parts to be forced together, much as if they were welded transition fit may range from a interference fit to a clearance fit between the mated parts line fit results in surface contact or clearance when limits are reached 9 Slide 10 EML 2023 Computer Aided Design Cylindrical Fits English Units The ANSI B4.1 standard defines a series of fits between cylindrical features in inches for the basic hole system. The types of fits covered in the standard are: RC: running or sliding clearance fits LC: clearance locational fits LT: transition locational fits LN: interference locational fits FN: force and shrink fits 10 Slide 11 EML 2023 Computer Aided Design Cylindrical Fits English Units RC: running or sliding clearance fits RC1 to RC9 LC: clearance locational fits LC1 to LC11 LT: transition locational fits LT1 to LT6 LN: interference locational fits LN1 to LN3 FN: force and shrink fits FN1 to FN5 11 Slide 12 EML 2023 Computer Aided Design Example RC9 Fit hole and shaft have a basic diameter of 2.5 From Tables in Appendix 29 thousands of an inch 12 Slide 13 EML 2023 Computer Aided Design Example LT3 Fit hole and shaft have a basic diameter of 2.5 From Tables in Appendix 31 thousands of an inch 2.5012 2.5000 2.5008 2.5001 13 Slide 14 EML 2023 Computer Aided Design Example LN2 Fit hole and shaft have a basic diameter of 2.5 From Tables in Appendix 32 thousands of an inch 2.5012 2.5000 2.5021 2.5014 14 Slide 15 Example Problem 15 Slide 16 EML 2023 Computer Aided Design Cylindrical Fits Metric Units ANSI B4.2 standard basic size the diameter from which limits are calculated upper and lower deviation the difference between the hole or shaft size and the basic size tolerance - the difference between the maximum and minimum sizes 16 Slide 17 EML 2023 Computer Aided Design Cylindrical Fits Metric Units 17 Slide 18 EML 2023 Computer Aided Design Cylindrical Fits Metric Units fundamental deviation a letter grade that describes the deviation closest to the basic size International Tolerance (IT) grade a series of tolerances that vary with the basic size to provide a uniform level of accuracy within a given grade there are 18 IT grades: IT01, IT0, IT1, , IT16 18 Slide 19 EML 2023 Computer Aided Design Cylindrical Fits Metric Units Hole basis a system of fits based on the minimum hole size as the basic diameter the fundamental deviation for a hole-basis system is H Appendices 35 and 36 give hole-basis data for tolerances Shaft basis a system of fits based on the maximum shaft size as the basic diameter the fundamental deviation for a hole-basis system is h Appendices 37 and 38 give shaft-basis data for tolerances 19 Slide 20 20 Slide 21 EML 2023 Computer Aided Design Cylindrical Fits Metric Units 21 Slide 22 EML 2023 Computer Aided Design Cylindrical Fits Metric Units 22 Slide 23 EML 2023 Computer Aided Design Example 1 determine the shaft and hole limits for: hole-basis system a close running fit a basic diameter of 49 mm use a preferred size 23 Slide 24 24 Slide 25 EML 2023 Computer Aided Design Example 1 use a preferred basic diameter of 50 mm use a fit of H8/f7 25 Slide 26 EML 2023 Computer Aided Design Example 2 determine the shaft and hole limits for: hole-basis system a location transition fit a basic diameter of 57 mm use a preferred size 26 Slide 27 EML 2023 Computer Aided Design 27 Slide 28 EML 2023 Computer Aided Design Example 2 use a preferred basic diameter of 60 mm use a fit of H7/k6 28 Slide 29 EML 2023 Computer Aided Design Example 3 determine the shaft and hole limits for: hole-basis system a medium drive fit a basic diameter of 96 mm use a preferred size 29 Slide 30 30 Slide 31 EML 2023 Computer Aided Design Example 3 use a preferred basic diameter of 100 mm use a fit of H7/s6 31 Slide 32 EML 2023 Computer Aided Design Nonstandard Fits, Nonpreferred Sizes determine the shaft and hole limits for: hole-basis system a close running fit a basic diameter of 45 mm (do not change to a preferred size) 32 Slide 33 33 Slide 34 EML 2023 Computer Aided Design Nonstandard Fits, Nonpreferred Sizes use a fit of H8/f7 34