Introduction to Technical Drawing

WEEK ONE (1)

BASIC TECHNOLOGY

GRADE SEVEN (7)

INTRODUCATION TO TECHNICAL DRAWING

INTRODUCTION

Technical drawing is an organized means by which technologist pass on information among themselves. Before an object such as car, bicycle, television, or building is produced or manufactured, the ideas of their various parts are first formed in the minds of the designers. These ideas are carefully presented in the form of drawings.

DEFINITION

Technical drawing is the language used by technical men and women to communicate their ideas. The idea takes a concrete shape with the drawing. A drawing can communicate technical details better.

DRAWING EQUIPMENT/INSTRUMENTS AND MATERIALS

Technical drawing is able to pass information accurately when it is neat and carefully drawn. Neatness and accuracy come with the proper use of the correct instrument. These are drawing board, drawing instruments and drawing materials.

DRAWING BOARD:

Is a rectangular piece of good quality wood with smooth flat surface. It is used to hold the drawing paper on the smooth flat surface. Tee square is attached to it.There are five commonly used standard sizes of drawing boards, namely A⁰  ,A¹, A²,A³, A⁴.The A² size drawing board, with dimension 420mm X 594mm, is very good for the use of students in junior secondary.

DRAWING PAPER:

A good drawing paper is thick, smooth, usually white and does not tear easily when erasing, example the cartridge type which can be purchased in rolls or sheets.

TEE SQUARE:

Is a T-shaped equipment, usually made of wood or Perspex. It has two parts-the stock and the blade. The blade is fixed at 90⁰ to the stock; the blade is a straight edge. When the tee-square is placed on the drawing board and the stock is pressed firmly against the left edge, the blade is used to draw lines that are at 90⁰ to the left edge.

SET SQUARE:

Is a right-angled triangular flat piece, usually made from transparent materials. It comes in two types,45^o set square and 60^o and 30^o set square. It is used to draw lines at 90^o to those drawn with the Tee-square. It is also used to draw other lines are inclined to vertical or horizontal directions.

PAIR OF COMPASS:

This consists of two legs joined at the top, one leg contains a pencil. The other leg is pointed and is meant to remain fixed on the paper. Compasses are helpful in drawing circles or circular shapes.

PAIR OF DIVIDERS:

The dividers are made up of two legs joined at the top, where both legs are pointed. The pointed ends of divider are placed on a section of a drawing or against the scale of a ruler. A divider is a tool for comparing size, dividing line segment and measuring distance on the drawing.

PROTRACTOR:

Is a transparent semicircular or in full circle form flat object with calibration in the range of 0^o – 180^o. It is used for measuring and drawing angles.

FRENCH CURVE/CURVES:

Curves are available in two forms, namely –Rigid and Flexible.The rigid type is made of perplex or polyvinyl chloride and is available in different shape and sizes. The flexible type can be bent to form any curve. Curves are Special aids for drawing irregular curves.

TEMPLATES AND STENCILS:

Is a piece of clear plastic with cut-out shapes for use in drawing. Its various patterns of various geometrical shapes, examples are squares, hexagons, circles, ellipses etc. used to facilitate the drawing of such shapes. Stencils are also patterns of letters and figures used for lettering.

RULERS:

Are made from plastics, metal, and wood, usually calibrated in metric units-millimeters (mm) or centimeters (cm).Rulers are used for measuring linear dimensions of objects. The ruler is used to measure the length, height or width of an object.

PENCILS:

Three grades of pencils are required for a good quality work a 2H, H, and HB. The 2 H pencil, which should be sharpened to a chisel point, is used for drawing all straight construction lines. The H pencil is sharpened to a conical point and is used for lettering, drawing arrowheads and to thicken visible outlines. The HB pencil sharpened to a conical point is used for freehand sketching.

PENCIL SHARPENER:

It contains a blade by which the lead and the wood are chipped away. Pencils used in technical drawing are usually sharpened using either the mechanical or small handy sharpener made of plastic. Pencil may also be sharpened with a razor blade or pen knife.

ERASER:

It is made from rubber, good quality soft rubber is needed to erase mistakes. This is an instrument by which pencils marks on papers can be erased or removed. A good quality eraser can remove pencil marks without making the paper dirty.

MASKING /DRAUGHTING TAPE:

A draughting /masking tape is convenient for fixing drawing paper on drawing boards. A good substitute is the sellotape.

CLIPS AND PINS

Clips and pins may also be used. Pins are useful in fixing the drawing paper to the drawing board. They have shape tips and should be handled carefully.

CARE OF DRAWING MATERIALS:

We should be careful while using the drawing instruments/equipment

PAIR OF COMPASS/DIVIDER:

To Maintain The Sharp Tip Of The Compass Or Divider, We Must Be Careful Not To Drop These Instruments On Ground Or Floor.

PROTRACTOR:

Avoid dragging the protractor on the ground or over rough surfaces, this could wear out the marking.

PENCILS:

Should keep it sharp and pointed, we can achieve this through sharpening it with a sharpener.

DRAWING BOARD:

Do not use pins on the board

Do not use it for other purposes than for drawing

Place it face down when not in use.

TEE-SQUARE:

Never use it as a walking stick

Never hit the edge against any solid object and do not use a sharp object such as a razor blade against its edge.

Keep its underside clean to avoid dirt on the drawing paper.

Clean the surfaces before use.

All drawing instrument must be kept in their packets after use.

Odoemene Emmanuel C

Subject Teacher

Greenoak International Schools