Engineering Graphics - Dimensioning Methods and General Rules of Dimensioning

Line Types:

In an engineering drawing, every line has a definite meaning. Various types of lines are used to represent different parts or portions of an object.


Lettering in Drawing:

Lettering plays a major role in engineering drawing. It indicates details like dimensioning, name of the drawing, etc. The use of instruments for lettering is not advised, as it will consume more time. Free hand lettering should be used instead.

Rules and Features:

- Lettering in drawing must be of standard height. The standard heights of letters used are 3.5mm, 5mm, 7mm and 10mm.

- Generally, the height to width ratio of letters and numerals are approximately 5:3.

- The height to width ratio of the letters M and W are approximately 5:4.

- Different sizes of letters are used for different purposes: Main Title - 7 or 10mm

Sub-title - 5 or 7mm

Others - 3.5 or 5mm.


The essential features of lettering used in engineering drawing are:

• Legibility

• Uniformity

• Similarity

Single stroke letters are the simplest form of letters and are generally used in engineering drawing.

Vertical Lettering:

Vertical lettering is upright, i.e. 90 ( to the horizontal.

Both uppercase or large and lowercase or small letters are used.



Inclined Lettering:

Inclined lettering has letters inclined at 75° to the horizontal and as for vertical lettering both uppercase and lowercase letters are used.



Dimensioning Methods:

Dimensioning is used to describe a drawing in terms of details such as the size, shape and position of the object as per the Dimensioning Code 11669 - 1986. Expressing these details in terms of numerical values, lines and symbols is known as dimensioning.

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