Presentation on theme: "Precision Dimensioning Engineering II. Dimensioning Rectangular Prisms."— Presentation transcript:
Precision Dimensioning Engineering II
Dimensioning Rectangular Prisms
Dimensioning Cylinders The diameter of cylinders should be dimensioned in the rectangular view (not the circular view). Cylinders without a hole passing through them only require one view.
Rectangular 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 Lines –Coordinate Dimensioning Without Dimension Lines
Coordinate Dimensioning with Dimension Lines
Coordinate Dimensioning without Dimension Lines (Baseline Dimensioning)
Tabular Dimensioning Tabular 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.
Dual Dimensioning – Position Method Millimeter value is placed above (or below) the inch value or separated by a dash.
Dual Dimensioning – Bracket Method Millimeter value is enclosed in square brackets. A note should be placed on the drawing such as: DIMENSIONS IN [ ] ARE MILLIMETERS.
Tolerance Dimensioning Why do we need tolerance dimensioning? –Interchangeable parts manufacturing –Parts are manufactured at widely separate localities –Effective size control –Modern industry relies on it for subcontracting and replacement parts Accuracy is Expensive, however
Reading Dimensions.1One tenth of an inch.01One hundredth of an inch.001One thousandth of an inch.0001One ten-thousandth of an inch.00001One millionth of an inch
Specification of Tolerances Bilateral-Equal Limit Dimension Bilateral-Unequal Unilateral
Tolerance Tolerance 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.0003.
Maximum 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.
Maximum Material Condition For the part shown here the MMC is since that size would yield the most material.
Allowance Allowance 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
More Terminology Nominal 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.
Clearance Fit Space is always left between parts. What is the allowance in this case? – =.0012
Interference Fit Always an interference of material. What is the allowance in this case? – = or just.0013
Transition Fit Fit might result in clearance or interference.
Line Fit Clearance or surface contact may result at assembly.
Basic 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).
Basic 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.
Specifying a Fit - Inches Nominal Size Range Inches Over To Class RC 1 Limits of Clear. Standard Limits Hole H5 Shaft g –0 –0.1 – –0 –0.15 – –0 –0.2 – –0 –0.25 – –0 –0.3 – –0 –0.4 –0.7 Determine type of fit and find corresponding table Determine basic size Find size range on table Determine tolerances for Hole and Shaft Remember values are in thousandths of an inch.
Specifying a Fit - Inches Nominal Size Range Inches Over To Class RC 1 Limits of Clear. Standard Limits Hole H5 Shaft g –0 –0.1 – –0 –0.15 – –0 –0.2 – –0 –0.25 – –0 –0.3 – –0 –0.4 –0.7 RC1 - Close Sliding Fit Basic size of Upper tolerance on hole is +0.4, which is really Lower tolerance on hole is -0. Upper tolerance on shaft is Lower tolerance on shaft is
Specifying a Fit - Inches Nominal Size Range Inches Over To Class RC 1 Limits of Clear. Standard Limits Hole H5 Shaft g –0 –0.1 – –0 –0.15 – –0 –0.2 – –0 –0.25 – –0 –0.3 – –0 –0.4 –0.7
Specifying Fits - Metric Basic Size Loose Running Hole H11 Shaft c11 Fit 1 Max Min Max Min Max Min Determine type of fit and find corresponding table Determine basic size Find size range on table Determine tolerances for Hole and Shaft
Specifying Fits - Metric Basic Size Loose Running Hole H11 Shaft c11 Fit 1 Max Min Max Min Max Min Loose Running Fit Basic size of 25