This document provides an overview of dimensioning rules for engineering drawings. It defines dimensions as numerical values that define the size, location, and other geometric characteristics of a part. There are different types of dimensions, including linear, angular, radius/diameter, and reference dimensions. Dimensioning systems include the aligned system, where dimensions are perpendicular to dimension lines and readable from the bottom or side, and the unidirectional system, where dimensions are placed to be readable from the bottom and dimension lines are broken in the middle. Guidelines are provided for dimension units in inches or millimeters and specifying the unit of measurement.

1. Basic of Engineering Drawing
Part-3
Dimensioning Rules
By
Prof. A.J.More
Department of Engineering Sciences

2. Contents:
• What are dimensions
• Fundamental rules of dimensioning
• Guidelines for good dimensioning in engineering drawings

3. Dimensions
• What are dimensions
• We use dimension to represent size and position (of the designed/modeled
shape)
• DIMENSION is a numerical value expressed in appropriate units of
measurement and used to define the size, location, orientation, form
or other geometric characteristics of a part.
• A method of communication to machinists in the Production facility
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4. Types of Diamensions:
• Different kinds:
• Linear
• Angular
• Radius/diameter
• Reference
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5. Dimensions- Basic terminology
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6. Dimension Units:
• Dimensions- units thanks to resources
• decimal inches, fractional inches, feet and fractional inches
• SI or metric – millimeter (mm)
• leading zero: metric – yes; inches – no
• If units (e.g., IN or mm) are not included with each dimension, specify the units
used with a note on the drawing; for example
• UNLESS OTHERWISE SPECIFIED, ALL DIMENSIONS ARE IN mm
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7. Aligned System
In the aligned system, dimensions are aligned with the entity being measured. They are placed
perpendicular to the dimension line such that they may be read from the bottom or right-hand side
of the drawing sheet. Dimensions are placed at the middle and on top of the dimension lines.
Unidirectional System
In the unidirectional system, dimensions are placed in such a way that they can be read from the
bottom edge of the drawing sheet. Dimensions are inserted by breaking the dimension lines at the
middle.
Systems of Dimensioning

8. Dimensioning systems
Aligned system
(readable from bottom and right edge of
sheet)
Unidirectional system
(visible from bottom edge)

9. Thank You