DRAWING INSTRUMENTS AND THEIR USES

Drawing instruments are used to prepare drawings easily, quickly and accurately. The quality of the instruments has a big impact on how accurate the drawings are. With instruments of good quality, desirable accuracy can be attained with ease. It is, therefore, essential to procure instruments of as superior quality as possible.

Below is the list of minimum drawing instruments and other drawing materials which every student must possess:

1 . Drawing board

2. T-square

3.  Set-squares - 45° and 30°- 60°

4.  Drawing instrument box, containing: (i) Large-size compass with inter-changeable pencil and pen legs (ii) Lengthening bar (iii) Small bow compass (iv) Large-size divider (v) Small bow divider (vi) Small bow ink-pen (vii) Inking pen

5.  Scales

6.  Protractor

7.  French curves

8.  Drawing papers

9.  Drawing pencils

10. Sand-paper block

11. Eraser (Rubber)

12. Drawing pins, clips or adhesive tapes

13. Duster

14. Drafting machine

15. Roll-n-draw.

We shall now describe each of the above in details with their uses:

TO CONSTRUCT SQARES

A) By using Ruler and set square:

 1. Using a ruler or T-Square, draw a line segment AB corresponding to the length of one side of the square.

2. Place the set square at one end of the line segment (i.e., A) and draw a perpendicular line that is longer than the side of the square.

3. Using the ruler, mark a point on this line that corresponds to the length of the side of the square.

4. Place the set square at another end of the line segment (i.e., B) and draw a perpendicular line that is longer than the side of the square.

5. Using the ruler, mark a point on this line that corresponds to the length of the side of the square.

6. Using the ruler, connect the two marks made in steps 3 and 5 to form the square.

B) By using T-square and set square:

1. Using a ruler or T-Square, draw a line segment AB corresponding to the length of one side.

2. At A and B draw verticals AE and BF

3.  From point A draw a line  inclined at 45 to AB, Cutting line BF at C.

4.  From point B draw a line  inclined at 45 to AB, Cutting line AE at D.

5. Draw a line connecting C and D.

6. Then ABCD is the required square.

C) By using compass:

1. Draw a line segment AB corresponding to the length of one side.

2. At A, draw a line AE perpendicular to AB.

3. With centre A, and radius AB, draw an arc cutting AE a D.

4. With centre B, and radius AB, draw an arc.

5. With centre D, and same radius draw an arc cutting previously draw arc from B.

6. Mark the intersecting point as C.

7. Draw lines C with B, C with D.

8. Then ABCD is the required square.

Construct an Equilateral triangle, given the length of side, using set squares

1. Draw a line using a scale of any length as AB.

2. With 30°-60° set square draw a line through A, making an angle 60° with AB.

3. Similarly , through B, draw a line making same angle with AB intersecting previously drawn line at C. 

4. Then ABC is the required triangle.

TO CONSTRUCT AN OGEE OR REVERSE CURVE

          An Ogee curve or a Reverse curve is a combination of two same curves in which the second curve has a reverse shape to that of the first curve. In other words, any curve or line or line or mould consist of a continuous double curve with the upper part convex and lower part concave, to some extent having shape of 'S'.