Technical Graphics - The Basics - Angles

It is very important to be able to draw angles in Technical Graphics. With your set squares sitting on your T-square you can four commonly used angles. These are 30°, 45°, 60° and 90°. You can see these below.

30°	45°	60°	90°

These are the basic angles and are easy to create using the set squares in the different orientations shown. Always make sure that the T-square is flush with the side of the drawing board and that the set squares are flush with the T-square.

Named Angles

There are five named angles. In the case of three of these named angles the names describe ranges of angles. In two of the cases a specific angle is named. These two angles are very important in terms of mathematics and you will come across them lots of times in your maths classes. In the diagrams below the angles are shown using red arrows.

Acute Angle This is any angle which is between 0° and 90° exclusive.

Right Angle This is an angle which is exactly 90°.

Straight Angle This is an angle which is exactly 180°.

Obtuse Angle This is an angle which is between 90° and 180° exclusive.

Reflex Angle This is an angle which is greater than 180°.

Exercise

Here is an exercise you can complete to practice creating some common angles with your set squares.

The drawing is based on an 80mm circle. The first curve to the 30° line is 20mm from the centre, and all subsequent lines are 5mm apart.