6Rectangular Coordinate Dimensioning Used when computer-controlled production machines are used to manufacture parts.The designer should consult with personnel in manufacturing to ensure that the origin is located in an appropriate position.Two types of rectangular coordinate dimensioning:Coordinate Dimensioning with Dimension LinesCoordinate Dimensioning Without Dimension Lines
8Coordinate Dimensioning without Dimension Lines (Baseline Dimensioning)
9Tabular DimensioningTabular dimensioning is used when a series of parts consists of the same features or geometry but vary in dimension.Letters are used in place of dimension values, and the values are then placed in a table.Most standard parts are dimensioned this way in catalogs, the machinery handbook, and in the back of most textbooks.
11Dual Dimensioning – Position Method Millimeter value is placed above (or below) the inch value or separated by a dash.
12Dual Dimensioning – Bracket Method Millimeter value is enclosed in square brackets. A note should be placed on the drawing such as: DIMENSIONS IN [ ] ARE MILLIMETERS.
13Tolerance Dimensioning Why do we need tolerance dimensioning?Interchangeable parts manufacturingParts are manufactured at widely separate localitiesEffective size controlModern industry relies on it for subcontracting and replacement partsAccuracy is Expensive, however
14Reading Dimensions .1 One tenth of an inch .01 One hundredth of an inch.001One thousandth of an inch.0001One ten-thousandth of an inch.00001One millionth of an inch
15Specification of Tolerances Limit DimensionBilateral-EqualUnilateralBilateral-Unequal
16ToleranceTolerance is the total amount a specific dimension is permitted to vary (difference between the maximum and minimum limits).The dimension below has a tolerance of
17Maximum Material Condition When specifying tolerance dimensions, the maximum material condition (MMC) means the product or part contains the maximum amount of material specified by the tolerance.The heaviest part.
18Maximum Material Condition For the part shown here the MMC is since that size would yield the most material.
19AllowanceAllowance is the minimum clearance or maximum interference intended between the maximum material condition (MMC) of mating parts.The allowance for the system below is: = 0.110
20More TerminologyNominal Size - General identification in fractions (ex. 1-1/2 for 1.500).Basic Size - General identification in decimal (ex ).Actual Size - Measured size.Limits - Maximum and minimum sizes indicated by the tolerance dimensions.
21Clearance Fit Space is always left between parts. What is the allowance in this case?– = .0012
22Interference Fit Always an interference of material. What is the allowance in this case?– = or just .0013
23Transition FitFit might result in clearance or interference.
24Line FitClearance or surface contact may result at assembly.
25Basic Hole System (Hole Basis) The minimum size hole is taken as the basic size. Used when standard tools are used to produce holes (reamers & broaches).
26Basic Shaft System (Shaft Basis) The maximum shaft size is taken as the basic size. When several parts having different fits, but one nominal size are required on a single shaft.
27Specifying a Fit - Inches NominalSize RangeInchesOver ToClass RC 1LimitsofClear.StandardHoleH5Shaftg40-0.120.10.45+0.2–0–0.1–0.250.150.5–0.15–0.30.20.6+0.25–0.2–0.350.250.75+0.3–0.450.30.95+0.4–0.550.41.1–0.4–0.7Determine type of fit and find corresponding tableDetermine basic sizeFind size range on tableDetermine tolerances for Hole and ShaftRemember values are in thousandths of an inch.
28Specifying a Fit - Inches NominalSize RangeInchesOver ToClass RC 1LimitsofClear.StandardHoleH5Shaftg40-0.120.10.45+0.2–0–0.1–0.250.150.5–0.15–0.30.20.6+0.25–0.2–0.350.250.75+0.3–0.450.30.95+0.4–0.550.41.1–0.4–0.7RC1 - Close Sliding FitBasic size of 1.500Upper tolerance on hole is +0.4, which is reallyLower tolerance on hole is -0.Upper tolerance on shaft isLower tolerance on shaft is
29Specifying a Fit - Inches NominalSize RangeInchesOver ToClass RC 1LimitsofClear.StandardHoleH5Shaftg40-0.120.10.45+0.2–0–0.1–0.250.150.5–0.15–0.30.20.6+0.25–0.2–0.350.250.75+0.3–0.450.30.95+0.4–0.550.41.1–0.4–0.7
30Specifying Fits - Metric BasicSizeLoose RunningHoleH11Shaftc11Fit1 MaxMin1.0600.9400.8800.1800.06020 Max20.13020.00019.89019.7600.3700.11025 Max25.13025.00024.89024.760Determine type of fit and find corresponding tableDetermine basic sizeFind size range on tableDetermine tolerances for Hole and Shaft