CAD/CAM Concepts Engineering Workshop MECHANICAL THEORY

Engineering Drawing Instruments-Uses and Importance

Engineering Drawing Instruments: Engineering Drawing Plays a crucial role in the life of Every Mechanical Engineering student because he has to bear that subject throughout his BTech.Apart from the Engineering Drawing, Production Drawing and Machine Drawing was also need to be learned by the Engineering student.

In Engineering Drawing, we have to draw and understand the largest buildings on a drawing sheet, not by reducing the dimensions but by reducing the scale. In order to measure any component, we need a set of Drawing Instruments in Engineering Drawing which are presented below.

Engineering Drawing Instruments
Engineering Drawing Instruments

Engineering Drawing Instruments:

The instruments used in engineering drawing are:

  1. Drawing sheet
  2. Drawing board
  3. Mini drafter
  4. Eraser
  5. Pencils
  6. Protractor
  7. French curves
  8. Templates
  9. Paper Holders
  10. Set squares
  11. Compass
  12. Divider

The Detailed explanation of above mentioned Drawing Instruments are shown below.

1.Drawing Sheet:

Drawing sheet is a white paper on which an object is drawn which is available in various sizes as shown below.

Drawing Sheet TypeDimensions (Length X Width) (mm)
A0841 X 1189
A1594 X 841
A2420 X 594
A3297 X 420
A4210 X 297
A5148 X 210

2. Drawing Board:

It is an object(table) on which the drawing sheet is placed. It is made up of wood and available in the rectangular cross-section. The drawing sheet is placed on the drawing board and is fixed by means of clips which are either plastic or metal materials.

The dimensions of the drawing board w.r.t length, width and thickness are presented below.

Type of Drawing BoardLength X Width X Thickness (mm)
D01500 X 1000 X 25
D11000 X 700 X 25
D2700 X 500 X 15
D3500 X 350 X 15

3.Mini Drafter:

It is used for drawing vertical lines, horizontal lines, inclined lines, parallel lines, angles, perpendicular lines, etc. Mini Drafter generally consists of two scales which are perpendicular to each other and are calibrated in ‘mm’. One end of the scale is to be connected to the edge of the table and the other end is used to mark and measure the dimensions.

4.Eraser:

It is used to rub the unwanted data from the drawing sheet. The eraser quality must be smooth such that it couldn’t tear the paper.

5.Pencils:

Pencils are the main drawing instruments used to draw the lines, circles, arcs, polygons, etc. w.r.t. the scale provided. Some of the pencils are hard and some of the pencils are smooth. The pencils which are hard are used to draw the construction lines and the pencils which are smooth are used to draw the main lines. Depending on the smooth and hard quality or the hardness, pencils are classified into 18 grades and they are as follows.

Grade of PencilHardness of Pencil
9HHardest
6H, 5H, 4HExtremely Hard
3HVery hard
2HHard
HModerately hard
FFirm
HBMedium hard
BModerately soft and black
2BSoft and black
3BVery soft and black
4B, 5B, 6BVery soft and very black
7BSoftest

Out of the above 18 grades of pencils, the following grades are used in engineering drawings.

Grade of PencilUsed to Draw
3HConstruction lines
2HDimension lines, center lines, sectional lines, hidden lines
HObject lines, lettering
HBDimensioning, boundary lines

6.Protractor:

A protractor is used to mark the angle w.r.t. point or a line. It is in the shape of a semi-circle which is transparent and made of plastic. It can measure an angle from 0-180 degrees. The center of this bottom line is marked with “O” or “C” from which the angles are measured.

7.French Curves:

These are irregular in cross section and were used to draw the small arcs and large splines which were not possible by means of a drafter. They are made up of plastic material.

8.Drawing Templates:

If you want to draw a circle of dia 4 mm, then it may not be possible with a compass. At that time, we need to use the templates. If you buy any geometry box for placing all the drawing instruments, then a drawing template was also given along with it which has Alphabets printed on it.

Similarly, in Engineering drawing, there are many things which cannot be drawn by the compass and that’s the reason drawing templates were invented.

9.Paper Holders or Clips:

The clips are used to hold the drawing sheet on the drawing board properly. Generally, 4 clips are used for any drawing sheet.

10.Set Squares:

Set squares are used to draw lines with an angle between them. In most of the structures, 30, 45, 60 and 90-degree lines are most common. 

Generally, set squares are of two types:

One is 45 degrees set square and another is 30 – 60 degree set square. Both are required in the drawing.

45 set square has a side of 25 cm while 30-60 set square has 25 cm length on one side.

11.Compass:

It is used to draw a line or a circle. It generally consists of two legs. One end has a sharp tip and the other end has a holder. The pencil is to be placed in that holder and is to be tightened by means of a screw.

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This is the detailed explanation of Drawing Instruments in Engineering Drawing. Hope this article is helpful to you. Please hit the SHARE button.

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