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  • 1. Tolerance andAllowance
  • 2. For more help contact meMuhammad Umair Bukhari Engr.umair.bukhari@gmail.com www.bzuiam.webs.com 03136050151
  • 3. Introduction Modern industry has developed on the basis of interchangeable manufacturing. Interchangeable manufacturing means production of parts to such a degree of accuracy as is necessary to permit assembly and proper functioning of parts without further machining or fitting. To set the dimension for many product we make certain gages that measure dimensions. So gages used for interchangeable manufacturing.
  • 4. Tolerance• “The total amount by which a given dimension may vary, or the difference between the limits.”
  • 5. Design Specifications and Tolerance Develop from quest for production quality and efficiency. Early tolerances support design’s basic function. Mass production brought interchangeability.
  • 6. Affected Areas Engineering ToleranceProduct Design Quality Control Manufacturing
  • 7. Product design Product Design has the responsibility of designing with consideration for the maximum possible working tolerances compatible with the functional requirements of the design.
  • 8. Manufacturing Manufacturing has the responsibility of bringing the design into a physical entity with consideration for process methodologies, capabilities and economics.
  • 9. Quality control Quality control has the responsibility of measuring and evaluating the final product to ensure the integrity of the product tolerance.
  • 10. Variation is Unavoidable• No two manufactured objects are identical in every way. Some degree of variation will exist.• Engineers apply tolerances to part dimensions to reduce the amount of variation that occurs.
  • 11. TolerancesA tolerance is anacceptable amountof dimensionalvariation that willstill allow an objectto functioncorrectly.
  • 12. TolerancesA tolerance is anacceptable amountof dimensionalvariation that willstill allow an objectto functioncorrectly.
  • 13. TolerancesThree basictolerances that occurmost often onworking drawingsare: limitdimensions,unilateral, andbilateral tolerances.
  • 14. Limit DimensionsLimit dimensions aretwo dimensional valuesstacked on top of eachother. The dimensionsshow the largest andsmallest values allowed.Anything in between thesevalues is acceptable.
  • 15. Limit Dimensions These are limit dimensions, because the upper and lower dimensional sizes are stacked on top of each other.
  • 16. Unilateral ToleranceA unilateraltolerance exists whena target dimension isgiven along with atolerance that allowsvariation to occur inonly one direction.
  • 17. Unilateral Tolerance This tolerance is unilateral, because the size may only deviate in one direction.
  • 18. Bilateral ToleranceA bilateraltolerance exists ifthe variation from atarget dimension isshown occurring inboth the positive andnegative directions.
  • 19. Allowance Allowance is a planned deviation between an actual dimension and a nominal or theoretical dimension, or between an intermediate-stage dimension and an intended final dimension
  • 20. example Outer dimensions (such as the length of a bar) may be cut intentionally oversize, or inner dimensions (such as the diameter of a hole) may be cut intentionally undersize, to allow for a predictable dimensional change following future cutting, grinding, or heat- treating operations.  For example:the outer diameter of a pin may be ground to 0.0005 inches (0.013 mm) oversize because it is known that subsequent heat-treatment of the pin is going to cause it to shrink by 0.0005 inches (0.013 mm). A hole may be drilled 0.012 inches (0.30 mm) undersize to allow for the material that will be removed by subsequent reaming.
  • 21. DifferenceTolerance ALLOWANCE A tolerance is the limit of  an allowance is acceptable unintended de a planned deviation from viation from a nominal the nominal or theoretical or theoretical dimension. dimension Therefore, a pair of  whereas allowance is one tolerances, upper and lower, defines a range that we give to the within which an actual material to undergo some dimension may fall while process in the future. still being acceptable.