Basic Dimensioning

Rules of Dimensioning

Working Drawing

Definition: A drawing from which a part can be produced.

Must be a complete set of instructions Consists of:

The views needed to describe the shape Dimensions needed for manufacture Notes (materials, etc.)

Dimensions are noted using:

Extension lines

Symbols

Notes

Dimension linesLeaders

Types of Dimensions

Overall dimensions overall length.width and height

Detail dimensions all other dimensions used to describe an object

The standard units measurement Metric = millimeters Imperial = inches Always specify full size dimensions

Place dimensions off between or above views

Dimension a feature where the shape is shown

Dimension a feature only once and always to an object line

Omit one detail dimension in a chain

Place consecutive detail dimensions in line

8-2 Dimensioning Circular Features

Diameters and radii

Cylindrical and slotted holes

Dimensioning Cylindrical Objects

Repetitive features

Dimensioned once with an indication of how many repetitions are required

Chamfers

Normally dimensioned using angle and linear length

Knurls

Expressed in terms of type, pitch, and diameter before and after knurling

Undercuts

Expressed as width by diameter

Plain Undercut

Polar Coordinate Dimensioning

Commonly used in circular planes or circular configurations of features.

Indicates the position of a point, line, or surface with a linear dimension and an angle.

Chain Dimensioning

A series of dimensions is applied on a point-to-point basis.

Chain dimensioning may allow undesirable tolerance accumulation.

Datum or Common-Point Dimensioning

Several dimensions are measured from a common point or line.