Understanding Dimensioning Techniques in Technical Drawings

Types of Dimensions

Dimension Series

Dimension series are easy to implement but can accumulate errors during manufacturing. They are suitable for conventional parts that don't require special machining, such as numerical control machining. This method involves a series of operations in the manufacturing process.

Parallel Dimension

In this system, all dimensions are oriented in the same direction. It's used when a reliable reference is needed, as it avoids accumulating manufacturing errors since all measurements originate from the same point.

Combined Dimension

Combined dimensioning merges serial and parallel dimensioning. While it simplifies dimension lines and maintains necessary measurements, it requires adding or subtracting measurements.

Progressive Dimension

This method references all measurements from a common origin point, often designated as point 0. It's well-suited for narrow parts machined using numerical control.

Coordinate Dimension

Coordinate dimensioning uses the axis of symmetry of various elements as a reference. Measurements are taken from a designated point, often labeled 'w', to represent the coordinates of these axes, always originating from the same point.

Measurements are used to determine the dimensions of the drawing represented in the plane. The elevation is indicated by a fine line (height line) with arrows at each end, defining the distance between points. This measurement is placed above the line.

Kinds of Dimensions

Functional Dimension

Functional dimensions are the primary dimensions required in a plan. They represent the critical measurements with maximum demand and must be directly displayed on the drawing. These dimensions are independent of other measurements and are also referred to as principal dimensions. In drawings, they are often labeled as 'F'.

Non-Functional Dimension

Non-functional dimensions represent measurements with wider tolerances or the maximum allowable tolerance. They generally don't have stringent requirements beyond defining the workpiece contour. In drawings, they are often labeled as 'NF'.

Auxiliary Dimension

Auxiliary dimensions provide additional information on the drawing but are not critical for machining. They serve as reference points. In drawings, they are often labeled as 'A'.