Tolerances and FitsChapter 16 in TextbookTolerance1. Direct Limits and Tolerance Values1. Direct Limits and Tolerance Values – Plus and Minus Dimensions2. Geometric Tolerance System3. Tolerance Specifications in Title Block4. Notes Referring to Specific ConditionsImportant Terms – Single PartSlide 10Important Terms – Multiple PartsFitting Multiple PartsSlide 13Shaft and Hole FitsSlide 15Standard Precision Fits: English UnitsBasic Hole System or Hole BasisBasic Hole System – G28-ABasic Hole SystemSlide 20Slide 21Metric Limits and FitsMetric Preferred Hole Basis System of Fits1SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyTolerances and FitsAutumn 200912SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyChapter 16 in TextbookAutumn 200923SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyToleranceTolerance is the total amount a dimension may vary. It is the difference between the maximum and minimum limits.Ways to Express:1. Direct limits or as tolerance limits applied to a dimension2. Geometric tolerances3. A general tolerance note in title block4. Notes referring to specific conditionsAutumn 200934SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of Technology1. Direct Limits and Tolerance ValuesAutumn 200945SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of Technology1. Direct Limits and Tolerance Values – Plus and Minus DimensionsAutumn 200956SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of Technology2. Geometric Tolerance SystemAutumn 20096Geometric Dimensioning and Tolerancing (GD&T) is a method of defining parts based on how they function, using standard ANSI symbols.Feature Control FrameConcentricity Symbol7SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of Technology3. Tolerance Specifications in Title BlockAutumn 20097General tolerance note specifies the tolerance for all unspecified toleranced dimensions.8SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of Technology4. Notes Referring to Specific Conditions8General Tolerances could be in the form of a note similar to the one shown below: ALL DECIMAL DIMENSIONS TO BE HELD TO .002" Means that a dimension such as .500 would be assigned a tolerance of 0.002, resulting in a upper limit of .502 and a lower limit of .4989SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyImportant Terms – Single PartNominal Size – general size, usually expressed in common fractions (1/2" for the slot)Basic Size – theoretical size used as starting point (.500" for the slot)Actual Size – measured size of the finished part (.501" for the slot)910SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyImportant Terms – Single PartLimits – maximum and minimum sizes shown by tolerances (.502 and .498 – larger value is the upper limit and the smaller value is the lower limit, for the slot)Tolerance – total allowable variance in dimensions (upper limit – lower limit) – object dimension could be as big as the upper limit or as small as the lower limit or anywhere in between1011SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyImportant Terms – Multiple PartsAllowance – the minimum clearance or maximum interference between partsFit – degree of tightness between two parts–Clearance Fit – tolerance of mating parts always leaves a space–Interference Fit – tolerance of mating parts always results in interference–Transition Fit – sometimes interferes, sometimes clears1112SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyFitting Multiple PartsAutumn 200912Part ATolerance of A Part BTolerance of B Fit Tolerance: Clearance or Interference13SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyFitting Multiple Parts1314SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyShaft and Hole FitsAutumn 2009Clearance Interference15SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyShaft and Hole Fits15TransitionCLEARANCE FIT+ .00316SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyStandard Precision Fits: English UnitsRunning and sliding fits (RC)Clearance locational fits (LC)Transition locational fits (LT)Interference locational fits (LN)Force and shrink fits (FN)1617SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyBasic Hole System or Hole BasisDefinition of the "Basic Hole System":The "minimum size" of the hole is equal to the "basic size" of the fitExample: If the nominal size of a fit is 1/2", then the minimum size of the hole in the system will be 0.500"1718SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyBasic Hole System – G28-AClearance = Hole – ShaftCmax = H____ – S____Cmin = H____ – S____Fill in the subscripts (min, max) in the equations above.18SMAXSMINHMAXHMIN19SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyBasic Hole SystemClearance = Hole – ShaftCmax = Hmax – SminCmin = Hmin – SmaxBoth Cmax and Cmin <0 – _________ fitBoth Cmax and Cmin >0 – _________ fitCmax > 0; Cmin < 0 – ___________ fitWhat types of fits are these?19SMAXSMINHMAXHMIN20SheetCourse: Introduction to Engineering Graphics and Visualizationcopyright 2010, Georgia Institute of TechnologyBasic Hole SystemClearance = Hole – ShaftCmax = Hmax – SminCmin = Hmin – SmaxBoth Cmax and Cmin <0 – Interference fitBoth Cmax and Cmin >0 – Clearance fitCmax > 0; Cmin < 0 – Transition fitSystem Tolerance =