Presentation on theme: "Dimensioning and Tolerancing"— Presentation transcript:
1Dimensioning and Tolerancing David QuigleyFebruary 7, 2006
2Dimensioning Definition: A dimension is a numerical value expressed in appropriate units of measure and indicated on a drawingA dimensioned drawing should provide all the information necessary for a finished product or part to be manufactured.
3Dimensioning ExampleAn example dimension is shown below.
4Rules for Dimensioning Use one type of dimensioning consistentlyGeneral units can be omitted if stated somewhere on the drawingProjection lines do not touch the object and are drawn perpendicular to the element you are dimensioning.All dimensions less than 1 should have a leading zero. i.e. .35 should be written as 0.35
5Types of Lines Thin chain lines indicate center lines. Dashed lines are for hidden lines.Center LinesHidden Lines
6Types of Dimensioning Parallel Dimensioning Has several dimensions starting from one projection line.
7Types of Dimensioning Chain Dimensioning Having the dimensioning start after each previous dimensionChains of dimension should only be used if the function of the object won't be affected by the accumulation of the tolerances.
8Types of Dimensioning Combined Dimensioning This type combines Chain and Parallel Dimensioning
9Types of Dimensioning Dimensioning Holes Holes can be dimensioned with coordinates
12How to dimension small objects When dimensioning small features, placing the dimension arrow between projection lines may create a drawing which is difficult to read. So, use one of the below techniques.
13Dimensioning CirclesAll dimensions of circles are proceeded by this symbol; .There are three different ways to dimension circles
14Circle Dimensioning (a) two common methods (b) Used when the circle is too small(c) outside dimensioning
15Tolerancing Definition: The total allowable variation an acceptable part can have from the specified dimension.The less variation allowed, the more the part will cost to make
17Tolerancing RulesEach dimension on a drawing must include a tolerance value.a general tolerance value applicable to several dimensions. i.e. a note specifying that the General Tolerance +/- 0.5 mm.or a tolerance specific to that dimension
18Tolerancing ExampleThe upper limit for the tolerance goes on top of the lower limit.
19Dimensioning Exercises Complete the Handout Exercise