CONSTRUCTION
MANUAL AND COMPUTER-AIDED
CONSTRUCTION DRAWING
HIGHER
STUDY GUIDE 1
Basic drawing skills
STUDY GUIDE 1: BASIC DRAWING SKILLS INTRODUCTION
Outcome 1
Utilise basic drawing skills in the production of drawings. On completion of this Outcome you should be able to:
• correctly select and use a range of drawing instruments and materials • accurately draw lines and shapes to different scales
• neatly letter, annotate and dimension drawings
• use the graphic conventions commonly adopted in construction drawing.
This Study Guide is designed to help you to develop the basic manual drawing skills required in construction drawing. The material is suitable for students with little or no experience of drawing board work. You may, however, already have studied
graphical communication and have acquired certain basic skills. The Guide will encourage you to practise such skills and extend them to the preparation of construction drawings to an acceptable industry standard.
Included in the Study Guide are a number of assignment sheets, which will allow you to gain experience in the correct use of instruments and graphic conventions.
EQUIPMENT AND MATERIALS
This section illustrates the types of drawing equipment and materials used in
construction drawing. The equipment considered is commonly used in architectural, civil engineering and building services drawing offices for the manual preparation of drawings.
Pencils
Pencils are extensively used in drawing and are very familiar to all students. However there is more to choosing the correct pencil for a drawing task than might first be realised.
Grades of pencil
Pencils are available ranging from 9H (extremely hard) to 6B (extremely soft). The type of paper to be drawn on affects the grade of pencil to be used – the rougher the paper the harder the lead which should be used. In drawing offices the main type of paper for finished drawings is tracing paper but rougher detail paper is often used for roughing-out the drawing. Different grades of pencil may be used on each type of paper.
The most important reason for using different grades of pencil is the effect that hardness can have on the finished drawing.
4H hard and dense
for accurate layouts
not for finished drawings – good for very light construction lines do not use with a heavy hand as this grooves the paper and may not erase easily
does not print well
2H medium-hard
hardest grade feasible for finished drawings does not erase easily if used heavily
F and H medium
excellent general purpose lead weight for layouts, finished drawings and lettering
HB soft
for dense, bold linework and lettering requires control for fine work
erases easily prints well
tends to smear easily
B-range pencils
these tend to smear too easily for use with T-square and set-squares but can be used to shade areas of the drawing to give effects.
Drawing on tracing paper allows offices to make copies on a photographic process called Dyeline Printing. In this process the tracing paper is placed over a
photosensitive paper and run through an intense light which burns off the blank areas and leaves the lines and shaded areas. Different densities of lines and shading show up on the finished developed print. Many effects can be achieved by using various grades of pencil, ink, colours, felt pens etc.
Aids to drawing straight lines
T-squares
These are used to draw all horizontal lines and to support the other pieces of equipment used to draw angled lines. If the T-square is kept in good condition the lines drawn will always be parallel and horizontal. The detachable T-square can be used to draw sloping lines over the length of the drawing which can be useful in the case of perspective drawing or large elevations which may require sloping ground lines. The fixed T-square or Parallel Action is found on many office drawing boards.
Edge of Drawing Board
Clear plastic drawing edge (use one side only)
Keep T-square Do not draw too close to end
Tight to edge of of the T-square as it may bend Drawing Board
Set squares
These are clear plastic triangles with set angles. There are two types:
1 45 Set squares - where the angles are 45 degrees and 90 degrees.
2 30/60 Set squares - where the angles are 30 degrees, 60 degrees and 90
degrees
These squares can be used to create a number of set angles in combination and sitting on the T-square.
Use of T-squares and set squares to draw lines
Having drawn a few good horizontal lines, pass on to the use of set-squares and the drawing of vertical and inclined lines Take the 45-degree set-square or the closed adjustable set-square and with this practise drawing lines, as shown in the figure. One edge of the set-square rests on the blade of the T-square and is held- in position-where required by the left-hand, which also holds the T-square firm. Lines are drawn with the pencil- along the other edges of the set-square in the directions indicated by the arrows. A number of parallel lines should be drawn bearing in mind the precautions mentioned above.
200
- 250
m
The 60-degree set-square- or the adjustable set-square set to this angle can be used similarly, as shown for vertical lines and lines at 60 degrees and 30 degrees to the horizontal.
By a combination of 45-degree and 60-degree set-squares it is possible to draw lines at 15 degrees and 75 degrees to the horizontal, as shown in the figure. This is worth trying a few times for practice, as there are three things to manipulate with the left hand; but it is seldom necessary to use this method, and the advantages of the adjustable set-square- which can be set to these and any angle in such cases is obvious.
When a number of lines are to be drawn parallel to an inclined line as may occur in-the setting-out of roofing, etc. in-the following method could be used. Place a set-square along the inclined line so that another of its edges is at right-angles to the line. Then gently-bring up the T-square until it is against this edge of the set-square, hold it tightly and then, by moving the set-square along the T-square to the required
positions, lines parallel to the first one can be drawn. This method should be practised with lines at varying angles.
Remember in all cases to keep the pencil well sharpened and held properly against the ruling edge.
Fig 1 Horizontal
Fig 2 Vertical and 45
Adjustable Set Square
This is useful for drawing any angle.
Scales
Scales are thin narrow strips of white or yellow plastic, or boxwood or ivory, with divisions along each edge usually on both sides. These divisions are in various recognised proportions to actual distances and dimensions, and can therefore be used for making new drawings ‘to scale’ or for measuring, by ‘scaling’, (as it is termed) existing drawings.
The two sides of the R.I.B.A. Approved Scale for metric drawings are shown overleaf. This is the scale now commonly used by architects. There are two lines of divisions along each edge in. the proportions of 1:10/1:100, 1:20/1:200, 1:5/1:5O, 1:25/1:2500.
Paper sizes
The advantages of standardised sizes for drawings are that they enable a more economical use of drawing and tracing paper, sensitised paper and cloth for prints, etc., to be made, and that the binding together and storing of the drawings becomes easier.
Standardisation is almost automatic when ‘A’ sizes are used and sheets of different size can be folded to a common size for filing in folders, for example Al sheet as illustrated.
Drawings for transmission by post or for loose storage can be similarly folded. In all cases the title block appears uppermost for ready reference.
LINE DRAWING AND SCALES
This section covers one of the most important aspects of good technical drawing, that is, the production of good quality lines of the correct weight and to the correct size.
Line weight
Line weight helps to convey meaning to a technical drawing.
• Important objects in the drawing can be highlighted by using heavier lines. • In Elevations the objects nearer to the viewer can be shown darker to make them
appear closer.
• Grid lines can be drawn faintly so as not to overcrowd the rest of the drawing. • Dimension lines can be drawn in very fine line.
All of the above help to give the drawing a more professional look as well as making the important parts stand out. There are no hard and fast rules as to the actual weight of lines to be used in each situation but the draughtsperson is left to apply judgement as to what would be suitable. In this respect a technical drawing becomes as much a graphical illustration as purely a factual drawing.
Typical line weights showing pencil used and appropriate situation
Line types
There are a number of situations in a Construction drawing where line weight is not enough to distinguish between different parts of the drawing.
• When different services or utilities, (gas, water, electricity) have to be shown on
the same plan.
• When different materials are used • Where hidden lines need to be shown • Where centre lines or grid lines are shown
In these situations it is common to use different line types to distinguish between them.
Colour is not an option in most cases as the final prints of drawings will usually be in grey-scale only.
Line quality
Line quality refers to:
• Crispness and clarity • Blackness and density; and • appropriate weight.
While inked lines vary only in width, pencil lines can vary in both value and width. Thus a pencil line’s weight is controlled by the density of the lead used (affected by grade of lead, drawing surface, humidity) as well as the pressure with which you draw.
It is essential that you understand as you draw what each line represents whether it is an edge, an intersection of two planes or simply a change in material or texture. All lines should start and end definitely; always touching at their ends, always bearing a logical relationship to other lines from beginning to end.
Drawing to scale
Construction drawing more often than not involves objects of considerable size. This means that a normal sized drawing board will not be able to accommodate the object drawn full size.
The draughtsperson must decide the following factors before arriving at a scale to use:
• How much detail needs to be shown
• What is the actual size of the object to be drawn • What size of paper would be most appropriate
• What is the normal convention for the type of drawing being produced.
The following are recommended scales for use with the metric system.
Use Scale Ratio
Maps 1:1000000 l mm to l000m 1:500000 l mm to 500m 1:200000 l mm to 200m 1:100000 l mm to 100m 1:50000 l mm to 50m Town surveys 1:50000 1 mm to 50m 1:20000 l mm to 20m 1:10000 l mm to l0m 1:5000 l mm to 5m 1:2500 1 mm to 2.5 m
Use Scale Ratio
Survey and layouts 1 :2500 1 mm to 2.5 m
1:2000 l mm to 2m
1:1250 l mm to l25m
1:1000 l mm to lm
1:500 l mm to 0.5m
Site and key plans 1:1250 1 mm to 1.25m
1:1000 l mm to lm
1:500 l mm to 0.5m
Sketch schemes, etc. 1:200 1 mm to 0.2 m
1:100 l mm to 0.lm Location drawings 1:200 1 mm to 0.2 m 1:100 l mm to 0.lm 1:50 l mm to 0.05m Component and 1:20 1 mm to 0.02 m assembly detail 1:10 1 mm to 0.01m drawings 1:5 1 mm to 0.005m 1:1 Fullsize
STUDY GUIDE 1: BASIC DRAWING SKILLS Assignment No1 – Line drawing
Hor iz onta l L ine s a t 6mm sp ac ing Ver ti cal L in e s at 6 m m s p aci n g 45 I n cline d L ine s a t 6mm s p ac ing Dr aw t h e li nes as s h own o n A3 pa per try ing t o m aint ain t h e s p ac ing th ro ugh out an d kee p in g the l ine d ens it y co ns ta nt .
STUDY GUIDE 1: BASIC DRAWING SKILLS Assignment No 2 – Use of scale rule.
LETTERING AND DIMENSIONING
This section covers other, important aspects of good technical drawing – adding notation text or lettering and dimensions to a drawing.
Lettering a drawing
The lines on a drawing are very important indeed but without some text to explain what the lines are the drawing would be of little use. Text is also used extensively in Construction drawing to give details of the materials and the types of construction, often called the Specification.
The process of adding text or notation to a drawing is called Lettering.
For normal drawing board work the usual lettering technique is called Hand Lettering. This involves very little if any assistance to the draughtsperson but relies only on the skill and expertise of that person.
There are many aids to lettering but all have their problems and special skills which must be learned before good results are produced. Some of these aids are mentioned for information but Hand Lettering is preferred as a good style produces an individual drawing which has the stamp of the person who drew it. (Some offices do not want individuality in their drawings and so insist on a particular aid being used on all drawings).
Stencils
These are available in a variety of sizes and styles but can only be used with ink and must be used with care. It is very difficult to prevent blotting of the ink and correct spacing of the letters and words is quite difficult. The correct thickness of pen is essential to produce acceptable stencilled lettering.
Press-on transfers
These can be used but have great problems in spacing and lining up.
Lettering machines
These are like very small computers which can have the notation typed in then the machine is placed on the required spot and set to print on to the drawing. These produce very good lettering but tend to look too clinical. They are also very expensive.
Typing to film
With this technique the notation is typed on to special clear film by a skilled typist. The film is then stuck on to the drawing in the required position. This technique is good as long as the film is very clear and does not cause a darker area round the notation. There is no doubt that this technique provides a good way of adding large volumes of type to a drawing such as in a specification.
General points on lettering
Size should be determined on the basis of:
1. readability from the observer’s point of view; and
2. the proportional relationship of the lettering to the overall size and
scale of the drawing.
Weight is determined by the size and value (ranging from white through a series of grays to black) of the letters; i.e., if a large-sized typeface is required for readability from a certain distance, but a low value is mandatory for a balanced composition then an outline letter should be used.
Placement of titles should be determined on the basis of their overall weight or tonal value and their role in the organisation of the presentation.
HAND LETTERING
STUDY GUIDE 1: BASIC DRAWING SKILLS Assignment No 3 – Lettering
Dimensioning
Dimensions are extremely important on drawings as it should never be necessary to scale sizes from copies of the drawing. The drawing will have been done to accurate scale but the copying process could distort the sizes and give false readings.
Dimensions should be easy to read but not dominate the lines of the drawing. This is quite difficult to achieve in practice but with care the minimum of dimensions will give the maximum information.
The dimension lines should be the faintest possible and should be well enough away from the objects so as not to interfere with them. The lettering size should be carefully chosen to be clear but not too prominent.
Some indications of good dimensioning style are given below but the actual layout will depend on the draughtsperson or the standard office style.
Complete Assignment Nos. 4 and 5
Typical Simple Dimensioning
Dimension line Extension line Tick Gap between extension line and object
Extension line should extend past dim. line Dim. line should extend past ext. line Alternative ways to
STUDY GUIDE 1: BASIC DRAWING SKILLS Assignment No 4 – Dimensioning of simple shapes.
Fix this sheet to your drawing board and dimension the shapes. Assume the shapes are drawn at 1:20 scale
STUDY GUIDE 1: BASIC DRAWING SKILLS Assignment No 5 – Dimensioning of floor plan.
Fix this sheet to your drawing board and dimension the drawing
:-Measure the sizes and dimension the outside perimeter of the building.
Measure the sizes and dimension the top part of the plan along the line
shown.
DRAWING SIMPLE GEOMETRIC SHAPES
This section covers the drawing of simple geometric shapes. Drawings consist of various simple geometric shapes arranged in such a way as to create other complex shapes. Often these complex shapes are again combined and so a complex drawing is made up from the very simple shapes such as line, arcs, circles, rectangles and
triangles.
Squares
Squares are simply regular rectangles with all sides equal and all angles right angles. This means that there are a number of ways in which a square can be drawn. In construction drawing it is essential that sizes are drawn accurately and so it is
recommended that all sizes should be measured individually. This does not mean that
using compasses, dividers and 450set square should not be done but that their use
should be carefully controlled.
There are many combinations of ways to draw all shapes and the methods shown above can be modified to suit conditions.
Rectangles
These are four sided figures with all the internal angles being right angles. They can be constructed in similar ways to Squares.
A B
C D
Draw AB along T-square to correct length Draw a line up fro B using th right angle on a set square to same correct length to C Draw a line back from C the same correct length to D A line drawn from D with the set square should meet A at exactly the correct length.
A
D C
B
A B
D C
Draw AB along T-square to correct length Draw a line up fro B using th right angle on a set square
Draw a line from A using the 45 set square C is where the 45 line meets the line fom B Construct point D in the same way using point B to start
Draw a line along the T-square from A Set the correct length of the sides on compasses Place the point on A and cut an arc on the line for point B Draw a line up from B using a set square
Place the compass point on B and cut the line for point C Continue from C for point D
A
B C
D
Draw a line from A using a 45 set square Measure the correct length fro A to B Use the 45 set square to set up line B to C Continue from C to D in the same way
Rhomboids
These are four sided figures which are parallelograms (opposite sides parallel) but in this case they do not have any right angles.
The lengths of the sides and one angle must be known to draw these shapes. Draw side A to B using the T-square and measure the length.
Set off the side AD to the known angle and measure the correct length. From D draw a line parallel to AB (in this case with the T-square). From B draw a line parallel to AD.
The intersection of the two lines gives point C.
Triangles
These are three sided figures. Drawing of a triangle requires:
• the sizes of the three sides
• the sizes of two sides and the included angle • the sizes of the angles and one side.
Special triangles are worth mentioning as they may be encountered in many drawings.
Equilateral triangles
These have three equal sides and three equal angles, each angle being 60 degrees.
Isosceles triangles
These have two equal sides and two equal angles.
Right angled triangles
These have two sides at right angles to each other.
Scalene triangles
These have unequal sides and unequal angles.
A B
C D
Drawing Triangles
Circles
Circles, Arcs (parts of circles) and other related shapes such as Ellipses form
important parts of drawings even though a lot of shapes in construction, especially in buildings are straight lines.
It is useful to have a knowledge of the terms used in relation to circles and curves.
A B
C
Draw line AB the required length Set the length AB on compasses Place the point on A and draw an arc Do the same with an arc from B Where they intersect is point C. The 60 set square can also be used by drawing 60 lines from A and B and using the intersection for point C
Equilateral Triangle A B
C
these angles from A and B to get
If the equal angles are known then draw lines at Where they intersect is point C.
Do the same with an arc from B Place the point on A and draw an arc Set the length of the equal sides on compasses Draw line AB the required length
the intersection for point C
Isosceles Triangle
A B
C
Measure the length AC on this line Join the points to form the triangle. Draw line AB the required length Drwa a line up at right angles to A
Right angled Triangle A B
C
ScaleneTriangle
Set the length of the side AC on compasses Place the point on A and draw an arc Where they intersect is point C. Do the same with an arc of length BC from B Draw line AB the required length
Useful Techniques in all Drawings
It is often necessary to perform some construction work on the drawing before a final shape can be achieved. The techniques required for these can best be illustrated by the following exercises which will look at:
• Bisecting angles • Filleting
• Joining lines and curves (same technique as filleting) • Dividing lines
• Drawing ellipses.
Bisecting an angle
1 Two lines with and unknown angle between 2 Strike an arc with compasses at any distance through each line.
3 Strike an arc from each intersection point on the line to meet each other as shown.
4 Draw the bisector line as the line from where the arcs meet to the intersection of the two lines
Filleting a curve between two lines
1 Use the technique above to bisect the angle.
2 Draw a line parallel to one of the lines at a distance equal to the fillet radius.
to cross the bisector line. 3 Extend the new parallel line
parallel lines
using this crossing as the centre. 4 Draw a circle to the required radius
The circle should just touch the lines and no more.
to leave the fillet and lines. lines and circle and erase the rest 5 Darken in the required parts of the
Dividing lines
1 Draw a line of any length and then
draw a line from one end at any angle. of any length and on any scale.2 Measure up the angled line, equal distances Join the point which marks the last division with the end of the first line.
down to the first line.
The first line will now be divided into the 3 Draw lines parallel to this new line, from the marks on the angled line
same number of equal divisions as the angled line.
Ellipses
As with most shapes there are a number of ways to draw an ellipse. The method shown uses the two axes of the ellipse, the Major and Minor, to construct circles then radiating lines from the centre to get co-ordinates on to the circumference of the ellipse. The more radiating lines which are used the smoother the ellipse can be drawn as the drawing will be free-hand.
Complete Assignment No 6
1 Major Axis
2 Minor Axis
3 Lines drawn from centre out to major axis
4 Lines drawn vertically down from major axis intersection
across from minor axis 5 Lines drawn horizontally intersection
6 Ellipse is drawn free-hand to join the points.
The more points the smoother the ellipse.
STUDY GUIDE 1: BASIC DRAWING SKILLS Assignment No 6 – Simple geometric shapes.
46mm 46m m 46m m 46mm 23mm 76mm 46m m 45° 80m m 66m m 70mm 160mm R45m m 100mm 50m m DIVISION OF A LINE SQUARES RHOMBOID SCALENE TRIANGLE CIRCLE ELLIPSE Arc Radius = 25mm
Line divided into 7 sections
Draw the shapes shown to the sizes given. Dimension the shapes as shown and add the text under each shape.
SYMBOLS AND BORDERS
This section covers the graphic conventions used to represent materials and standard objects in construction drawing. It also covers the means of finishing drawings through the addition of borders and titles.
Graphical Symbols
These are useful shortcuts to adding information to drawings. Many features are standard on all drawings and are represented on the drawing by symbols which should be those recommended in BS 1192.
The symbols generally take up less space on the drawing than the actual object and so do not tend to obscure other important features. They should be large enough to be located easily and be recognisable.
Typical Plumbing and Drainage Symbols Used on Services Plans and Site Layout Plans
Typical Symbols or Hatching used in construction drawing to distinguish between materials.
Borders
Borders fulfil two functions namely:
1. They frame and enclose the drawing giving it a finished appearance.
2. They provide an area of paper round the edge of the drawing which might become damaged without affecting the information on the drawing.
BS 1192 recommends that borders are placed in such a way that important
information about the drawing and the project will be visible when the drawing is folded for storage or posting. This usually means that a title box is incorporated in the border and is best placed at the right edge of the drawing usually at the bottom of the paper.
Most professional offices have a standard layout for borders and title blocks which usually has a space for the office title, name of the project, drawing number, drawing title, scale, date, responsible person and any other information thought appropriate. It is also common to have space above the title box to list and date amendments to the drawing. Many offices have their drawing sheets pre-printed showing all the
information to save drawing it on every time.
The BS recommendation is often not appropriate for student drawings as the paper size is often limited and such a border and title box takes up too much space.