Computers have becomes heavy source of designing and technical drawing nowadays. It is possible to complete engineering drawing in lesser time with high accuracy compared to manual drawing by using computers. Despite the prevalence of computer aided drafting, many older architects and even some structural designers still rely on paper and pencil graphics produced on a drafting table. So it is recommended to have a sound knowledge of this subject in which you will learn how to draw engineering sketches first on paper.
Manual drafting on paper is not possible without drawing instruments. Quality of drawing is also dependent on instruments used to draw particular drawing. For example if your compass is loose then you might not get exact radius of circle that you want to draw as per in data.
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Following is the list of drawing instruments that required making engineering drawings on paper with perfection.
- Drawing Board
- Mini drafter
- Set-squares (45° – 45° & 60° – 90°)
- Protractor (180°, 360°)
- Roll & Draw
- Compass (drafting)
- Circle Master
- French Curves
- Drawing paper & drawing sheet
- Drawing pencil (Lead pencil [Mechanical Pencil], wooden pencil)
- Drawing pins & clips
- Duster or handkerchief
1. Drawing Board
Drawing board is a desk or flat surface with proper dimensions used to support sheet and make it flat and ready to for technical drawing.
More recently engineers and draftsmen use the drawing board for making and modifying drawings on paper with ink or pencil. Some drafting tables incorporate electric motors to provide the up and down and angle adjustment of the drafting table surface.
2. Mini Drafter
It is an instrument used to draw geometrical shapes and figures with great precision. It does not require any other instrument like scale or set squares.
The mini-drafter is a versatile tool and can be used to draw almost everything. It can be used to draw parallel lines, perpendiculars, inclined lines of any degree with unmatched speed. It consists of one long scale and one small scale and the scales are in ‘L’ shaped which can be fit on any drawing board easily.
3. Set-squares (45° – 45° & 60° – 90°)
A set square is an object used in engineering and technical drawing, with the aim of providing a straightedge at a right angle or other particular planar angle to a baseline.
These set squares come in two usual forms, both right triangles: one with 90-45-45 degree angles, the other with 30-60-90 degree angles.
A T-square is a technical drawing instrument used by draftsmen primarily as a guide for drawing horizontal lines on a drafting table.
It may also guide a set square to draw vertical or diagonal lines. Its name comes from its resemblance to the letter T. The top of the T-square hangs off of the drafting table and is called the head; the blade is the part that stays on the drafting table. The T-square usually has a transparent edge made of plastic which should be free of nicks and cracks in order to provide smooth, straight lines.
5. Protractor (180°, 360°)
A protractor is a square, circular or semicircular tool, typically made of transparent plastic, for measuring angles.
Most protractors measure angles in degrees (°). Radian-scale protractors measure angles in radians.
Semi-circular protractor is of 180° and full circle protractor is of 360°. More advanced protractors, such as the bevel protractor, have one or two swinging arms, which can be used to help measure the angle.
6. Scales (Ruler)
A ruler, sometimes called a rule or line gauge, is an instrument used in geometry, technical drawing, printing and engineering/building to measure distances and/or to rule straight lines. You’ll need to use this instrument frequently for making technical drawing. The scales are available in plastic, wooden and steel material. Generally steel rule is used to draw engineering drawings.
7. Roll & Draw
Roll & Draw is most handy instrument for making charts & parallel lines at super fast speed. It is also popular as “A draftsman’s best friend.”
Furthermore, it is a multipurpose drawing instrument that lets you measure in centimeters and draw quadrants, squares, circles, angles, crosshatching, and vertical and horizontal parallel lines, quickly and easily.
8. Compass (Drafting)
A compass is a technical drawing instrument that can be used for inscribing circles or arcs. A typical compass is consists of two legs. One pencil lead is added to a leg and a tip point to pivot on paper is provided to another leg. Circles can be made by fastening one leg of the compasses into the paper with the spike, putting the pencil on the paper, and moving the pencil around while keeping the hinge on the same angle. Drafting compass is available in different variants that can be selected as per drawing requirement.
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9. Circle Master
Circle Master is very helpful template type drawing instruments which helps to draw circles of different radius at high speed. It eliminates use of compass as circle of fixed radius can be drawn.
It is a flat plate or circular plate with different sized holes punched at surface as shown in figure. If you want to draw circle of radius other than circle radius punched then it is required to use other drafting instrument as radius of circle cannot adjusted.
10. French Curves
A French curve is a template made out of metal, wood or plastic composed of many different curves. It is used in manual drafting to draw smooth curves of varying radii. The curve is placed on the drawing material, and a pencil or other implement is traced around its curves to produce the desired result.
11. Drawing Paper & Drawing Sheet
Generally a clean white paper or Sheets of sized varied from A1, A2 (most common), A3, A4 is used to make technical drawings on it.
12. Drawing Pencil (Lead pencil or mechanical pencil, wooden pencil)
A mechanical pencil is a pencil with a replaceable and mechanically extendable solid pigment core called a lead. It is designed such that the lead can be extended as its point is worn away. The lead is usually graphite based and can easily remove and placed by pushing tip at top of mechanical pencil. Drawing pencil comes in wooden material too that are useful to draw sketches in shades. Different shades or grades of mechanical pencil are shown in figure at left.
A pencil sharpener is a device for sharpening a pencil’s writing point by shaving away its worn surface. It is mostly used when wooden pencil is selected to draw sketches as used writing point of wooden pencil may blur the drawing that results in black damage to paper.
An eraser is used for removing pencil markings on paper or sheet. It is very helpful in removing unnecessary line of drawing by rubbing it on unwanted lines and points.
15. Drawing pins & clips
Drawing clips are used to hold drawings on drawing boards which remove sheet movement while working. Drawing pins are used to attach two or more sheets together. They are inserted and removed by hand, hence the terms “thumbtack” and “push pin” is also used. The term drawing pin comes from their being used to hold drawings on drawing boards.
16. Duster or handkerchief
Duster or handkerchief is often used to clean paper on which drawing is going on. They are available in different variants. Maximum dust is possible when you use eraser to erase something on paper. The duster is very helpful at that time as removal of dust from hand leads to more black spots on drawing paper. Above are the basic but mostly used drawing instruments. All are easily available in stationary shops at your local place. You should use them to make precise drawings exactly as per data given.
Scales in Technical Drawing
There are mainly three types of scales: (1) Full Scale (2) Reduced Scale (3) Enlarged Scale.
(1) Full Scale : Using Full scale means you are drawing object’s all lines and points as per in drawing data. If we study it further, Drawing is in Full Scale if dimensions in data and the dimensions in drawing are same. Let us take an example: One circle’s radius is 20 mm in data and you are drawing it of 20 mm in drawing then you are using full scale in drawing. Example: 1:1, 2:2, 3:3, 4:4, 5:5 etc.
(2) Reduced Scale: Using Reduced scale means you are drawing object’s all lines and points by reducing it to some points. Let us take an example: One circle’s radius is 20 mm in data but you are drawing it of 10 mm in drawing then you are using reduced scale in drawing. Example: 1:2, 1:3, 1:4, 1:5, 1:6 etc.
(3) Enlarged Scale: Using Enlarged scale means you are drawing object’s all lines and points by increasing or enlarging it to some points. Let us take an example: One circle’s radius is 20 mm in data but you are drawing it of 40 mm in drawing then you are using enlarged scale in drawing. Example: 2:1, 3:1, 4:1, 5:1, 6:1 etc
BIS-SP 46 Standards
In Brief About BIS – SP 46 Standards of Engineering Drawings & Other Commonly Used Standards in Engineering Drawing Practice. The BIS-SP 46 – 1988 is the standard which is for “Engineering Drawing Practice for Schools & Colleges”. And used in the educational institution for engineering drawing or graphics.
It was recently revised as SP – 46 – 2003. Other than this the following standards are commonly used in engineering drawing practice:
- IS 1444:1989 DRAWING BOARD SPECIFICATION
- IS 15021:2001 PROJECTION METHODS
- IS 3221:1966 DRAWING INSTRUMENTS
- IS 10713:1983 SCALES IS 10714:2001 LINES
- IS 9609:2001 LETTERING
- IS 11669:1986 DIMENSIONING
- IS 10711:2001 SIZE & LAYOUTS OF DRAWING SHEETS