xt7tht2g8b2w https://exploreuk.uky.edu/dips/xt7tht2g8b2w/data/mets.xml United States. Work Projects Administration. Kentucky 1942 books This digital resource may be freely searched and displayed in accordance with U. S. copyright laws. Kentucky Works Progress Administration Publications Mechanical drawing Manual of instructions, engineering drawing ; property identification and mapping project text Manual of instructions, engineering drawing ; property identification and mapping project 1942 1942 2012 true xt7tht2g8b2w section xt7tht2g8b2w I N UTIIVIEFEITY OFGKEIAJTUQSY V   ' _
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I   _.» MANUAL OF INSTRUCTIOVG A
  EEGI3'F3ITRING TIRATIING
_ PROPERTY IDENTIFICATION AND MAPPING PROJECT
I  _ TECHNICAL SERIES KY -· 5 '
I   WAR SERVICE SECTION
SERVICE DIVISION
l WORK PROJECTS ADMINISTPJITION IN KENTUCKY
  Louisville, Fabrxmry EO, 1942 ,~”
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pe P R E F A C E
This is the third in a series of technical manuals, issued by the
‘Tar Service Section, Service Division of the Work Projects Administration
in Kentucky. It is hoped that it will serve both as a guide to supervisors
· in instruction of workers and to workers themselves being trained for Eng-
ineering Drawing. It is not our intention to cover the field completely
but rather to treat the fundamentals with a view to training workers in
the drafting of property identification maps. A decimal page and chap-
ter numbering system is used allowing for the insertion of revised pages.
Credit for the preparation of the manual should be extended to the
. staff of the Property Identification and Mapping Project. The greater part
l of the material was selected and prepared by Karl Boggs and Henry H. Lovett,
Jr., Technicians. Walter M. Hoefclman, State Supervisor, arranged the ma-
terial and reviewed the text. Thomas P. Lynch, Technician, reviewed the
text and contributed useful ideas. Suggestions for improvement of the
Manual are invited.
et February 20, 1942 Donald P. Brown
5 State Supervisor
ji War Service Section
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V ’

 TABLE OF CONTENTS
pp l PREFACE . . . . . . .°..¤ . . . . . . . . . . . . . . .5.0.1
O
CHAPTER 1
INTRODUCTION . . . . . . . ................ 5.1.1
Types of Drawings . .°.. . . . . ...... . .5.1.1
Architectural . . . . . . ....¤..... .5.1.1
· `Working Drawings . . . . . . . . .... . . .5.1.2
Engineering . . . . . . ............ 5.1.5
Profiles . . . . . . . . . . . . . . . . .5.1.5
· Structural . . . . . . . . . . . . . . . .5.1.4
Maps . . . . . . . . .... . . . . . . .5.1.5
Type of Maps . . . . .... . . . . . . . . . . .5.1.6
Charts, Graphs, and Diagrams . . . . . . . .... .5.1.8
CHAPTER 2
INSTRUMENTS AND MATERIAL . . . . . . . . . . . . . . . . .5.2.1
• Drawing; Board . . . . .‘ . . . ......... . .5.2.1
T-square . . . . . . . . . . .... . . . . . . .5.2.2
Triangles . . . . . . . . . . . . . . . . . . . . .5.2.5
Scale . . . . . . . . . . . . . . . . . . . . . . .5.2.4
Dividers . . . . . . . . . . . . . . . . . . . . . .5.2.6
Compass . . . . . . . . . . . . . . . . . . . . . .5.2.7
I
Ruling Pens . . . . . . . . . . . . . . . . . . . .5.2.9
French Curves . . . . . . ...... - ..... . .5.2.11
NO
" $3 317 `

 ..2-
SELECTION OF MATERIAL . . . . . . . . . . . . . . . .... .5.5.1
PAPER . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.5.1
O
Detail . . . . . . . . . . . . . . . . . . . . . . . .5.5.1
Tracing . . . . . . . . . . . . . . . . . . . . . . .5.5.1
Tracing Cloth . . . . . . . . . . . . . . . . . . . . . . . .5.5.2
Pencils . . . . . . . . . . . . . . . . . . . . . . . . . . .5.5.2
Ilfllr. • • • • • • a • a • • • ¤ o • • 0 • • • • • • a • • a • |5•5•5
Drasers and Shield: . . . . . . . . . . . . . . . . . . . . .5.5.5
Thumb Tacks and Scotch Tape . . . . . . . . . . . . . . . . .5.5.4
CIDXPTEZR 4
O
PRACTICE ILXEILCICEFCS . . . . . . . . . . . . . . . . . . . . .5.4.1
Q Pencil . . . . . . . . . . . . . . . . . . . . . . . . . . .5.4.1
Freehand . . . . . . . . . . . . . . . . . . . . . .5.4.1
Scaling . . . . . . . . . . . . . . . . . . . . . .5.¢i.l
Letiering P. . . . . . . . . . . . . . . . . . . . . . 5.4.2
Single Stroke Lettering . . . . . . . . . . . . . . . 5.4.2
• Dividers . . . . . . . . . . . . . . . . . . . . . . 5.4..%
Compass . . . . . . . . . . . . . . . . . . . . . . 5.4%.6
French Curves and Irregular . . . . . . . . . . . . . 5.4%.7
T-square r=·.1..d Triangle . .. . . . . . . . . . . . . . . 5.4.7
Ixdcing . . . . . . . . . . . . . . . . . . . . . . . . . . .5.4.1/L
Ruling Pen . . . . . . . . . . . . . . . . . . . . . .5./1.14
Compass . . . . . . . . . . . . . . . . . . . . . . .5.#i.lé
Lettering . . . . . . . . . . . . . . . . . . . . . .5.4.15
· l—.=Iech¤,nica1 Lettering; . . . . . . . . . . . . . . . . .5.4.15

 -5..
CMPTER 5
— PLOTTING..............-.V.. . . .... 25.5.1
U   Prctrcctcr . . . . . . . . .- . . . . . . . . .5.5.1 A
Practice Exercises . . . . . . . . . . . . . .3.5.4
CHAPTER 6
MAPPING . . . . . . . . . . . . . . . . . .... . .5.6.1
Practice Exercises . . . . . . . ...... .3.6.2
Hep Symbols . . . . . . . . . . . . . . . `. . .3.6.2
Psntcgraph . . . . . . . . . . . . . . . . . .5.6.2
Plamimeter . . . . . . . . . . . . . . . . . .5.6.5
· Exercises . . . . . . . . . . . . . . . .5.6.5
CIIAPTER '7 V
PLATE 1 to 12 . . . . . . . . . . . . . . . . . .5.7.0
CHAPTER 8
CONVERSION TABLES
Pcles tc feet . . . . . . . . . . . . . . . .1 .5.8.1
Chains to feet . . . . . . . . . . . . . . . .3.8.2
I, CHAPTER 9
GLOSSARY ..............._.......5.9.1
CHAPTER IO
BIBLIOGRAPHY . . . . . . ...... . ........ 5.10.1
O

 5,l,l ‘
 
Chapter l
` INTRODUCTION
EHGIHTERING DRAFTING
O
A k` Engineering Drafting is drawing as used in the industrial world by
engineers and designers. It is the language in which they express and
record the ideas and information necessary for the building of machines
and structures, and for may making. Since engineering drawings depict
only the outline of an object, the lines must give exact and positive
information concerning every detail of the machine or the structure as
it exists in the designer's mind, in order that the user of his drawing
· will understand its meaniiajg and be able to construct the ol.>_}cct from it.
To the enginner it is a conyleto graphical language, by means of which he
describes minutely ever] necessary construction operation and keeps a com-
plete record of his work for duolication, repairs, or addition by others.
TYPES OF DRAWINGS
· é.2sai1>2¤.¤...ml
Eharacteristic ing. The general principles of
drawing are the same for all types of technical work, Each branch of the
engineering profession requires its own special application of the princi-
ples of mechanical drawiny and the employment of particular methods, symbols,
and conventions, In architectural drawing the necessary smallness of scale
requires that the general drawings be nade up largely of conventional syrv
bols indicating the various warts of the project undertaken. Since so
many notes of explanation and information concerning material and finish
I
are required, it is impossible to include all of them on the drawings.
They are therefore written separately in a document culled "Spccifications“
  4

 5.l.Z
which is either attached to, or made a part of the drawing itself. These
specifications are complementary to the drawings and have equal importance
and weight, A l
· In the makeup of an architect's drawings there is an evidence of artis-
` tic feeling, produced in part by the freehand work and lettering, and in
part by the use of finer lines, which gives them an entirely different ap-
pearance from that of a set of machine drawings, One peculiarity found in
many architectural drawings is the tendency to overrun corners. This in
an experienced draftsman's 1* .·. ork, gives a certain snap and freedom, however,
it is often a license fer carelessness and is therefore discouraged. The
more clear cut the drawing, the more reason for the user to be careful in
. following the design.
Working Drawing
A working drawing is a drawing which gives all the information necessary
for the complete manufacture or construction of the project represented.
Further, it is a technical description of a machine, structure, or map de-
- signed for a definite purpose and must convey all the facts regarding the
· project in question so clearly and explicitly that further instruction con-
cerning either manufacture, erection, or use will not be required, This
type of drawing includes the following:
l. A full graphical representation to a definite scale of the shape
- and relationship of every part of the object (shape description).
2, The figured dimensions of all parts (size description).
5, Explanatory notes giving specifications in regard to materials,
finish, heat treatment, etc.
· 4. A descriptive title.
Often, as in architectural and structural drawing, the notes of explan-
ation and information concerning details of materials and workmanship are

 3,l,S
too extensive to be included on the drawings, and are made up separately in
l typed or printed form and called the “specifications“, These are considered
a part of the drawing, the information in them having equal weight and im-
I
T portance with that shown on the drawing itself, Thus we have the term
"drawings and specifications“,
Although pictorial drawings are used to some extent in special cases,
the basis of any working drawing is orthographic projection. To represent
an object completely at least two views will be necessary, sometimes more,
The general rule governing the number of views is to make as rggiljggnwiiys
EEE; ;@n;;n;E§jLplearly and explicitly, Instances
may occur in which the third dimension is so well understood as to rake
O
one view sufficient, i,e, the drawing of a shaft or bolt. ln other cases
perhaps a half dozen views might be required to describe the project
completely.
aznjiaaaaine
There are several different types of engineering drawings. we will
discuss only those that are most commonly used by Engineers, _
. l. Eloilles. The type of drawing more commonly used by civil en-
gineers is the ordinary profile, a vertical section taken along
a given line either straight or curved, Such drawings are
necessary in problems of railroad construction, highway and street
hmvrovements, sewer construction, and other projects involving a
study of the surface of the ground. Frequently draftsmen other
than those in civil engineering are called upon to make these
drawings. Profiles are drawn on special types of paper which
· are called profile and cross—section paper. ln making a profile
drawing the horizontal distances are plotted as abscissas and
i elevations as ordinates. The vertical distances representing
  '

 5.l.4
elevations are plotted to a larger scale; thus vertical exagger-
ation is obtained in relation to the horizontal scale, which is
· necessary in studying the profile for the establishment of grades.
The vertical scale and horizontal scale is sorntizes confusing to
the layman or inexperienced draftsman, but ordinarily a profile
would fail in its purpose if the horizontal and vertical scales
were the same. Further, the profile unless so arranged would not
only be too long and unweildy, but difficult to make,
2, Structural. Structural drawings differ from other drawings only
. in certain details ard practices, which have developed because of
. peculiarities in the materials used, and their aaethod of fabrica-
tion. These differences are so well established, that it is essen-
tial for the draftsman to know the methods of representation in
structural drawing, '
Steel structures are wade of steel bemas and plates put to-
gether permanently by riveting or welding, The function of a
structural drawing is to show the shapes and sizes used and the 4 -
O
details of fastening, The structural draftsman must be familiar
with the dimensions of the various sizes of stwidard steel beams,
together with much other information before an accurate drawing
can be made. The general drawings correspond in many respects to
the design drawings and assembly drawings of the mechanical engi-
neer, giving the sizes and weights_of members and the number and
spacing of all rivets, but in most cases the general dimensions,
positions, and sizes of the members and the nuxber of rivets are
· shown, leaving the details to be worked out in the shop or to be
given on separate complete detail shop drawings. In order to show
the details clearly the structural draftsnan often uses two scales
  l

 ’ _ 3.1.5
draftsman often uses two scales in the same view, one for the center
. lings or skeleton of the structure showing the shape, and a larger
one for the parts composing it.
I
5. ygpi. In the treatment of various types of drawing the three dimen-
sions of an object have been represented either pictorially or by
drawing two or more views. In map drawing, the representation of
features on parts of the earth’s surface, there is the distinct diff-
erence in that the drawing is complete in one view. The third dimen-
sion is represented either by contour or hachure lines or omitted if
it is not required for the particular purpose for which the map is
· made. The surveying and mapping of the site under consideration is
the preliminary work in engineering projects. All engineers should
be familiar with the methods and symbols used in this branch of
drawing. It is not the purpose here to treat in detail the practice
of surveying and plotting or the various methods used by cartograph-
ers in projecting the curved surface of the earth on a plane, Rather
it is intended only to discuss the use and details of execution of
· plats and topographic maps. See (Raisz Erwin, "General Cartography,“
New York, 1958 p. 71 — ll7),
The content or information on maps may be classified in general under three
divisions:
l. The representation of imaginary lines, such as divisions between
areas subject to different authority or ownership either public or
private, and lines indicating geometric measurements on the ground.
In this division may be included plats or land maps, famn surveys,
· city subdivisions and plats of mineral claims,
2, The representation of real or material features or objects within
n

 ’ 3,l,G
the limits of the tract, showing their relative location or size
depending upon the purpose of the map. When relative location
· only is required the scale may be small, and symbols may be em-
ployed to represent objects such as houses, bridges, or even
towns, When the size of the object is an important consideration
the scale must be large and the map becomes a real orthographic
top view,
5. The representation of the relative elevation of the surface of
the ground. Maps with this feature are called relief maps, or
if contours are used with elevations marked on them, contour
. maps. Various combinations of these three divisions are required
for different purposes,
EXpe_pf maps
Classified according to their purpose, maps may be geographic, topo-
graphic, cadastral, engineering, and planimetric.
gepgraphic maps include large areas and consequently must be to
a small scale; They contain political boundaries, the more inn `
I
portant towns and cities, streams, bodies of water, and symbols
. for mountain ranges,
Topographip_maps are complete descriptions of specific areas to
a larger scale. The content is the same as that depicted on
geographic maps, with the exception that contour lines rather than
symbols are used to indicate elevations,
Qadastpalpmaps are control maps for cities and towns, drawn to a
large scale with all features including boundary lines accurately
· scaled, They are used to control city development and operation,
particularly taxation,
Engineering maps are working maps for engineering projects which
  A

 3.l.7
accurately delineate property lines, all objects on the site, and
contour lines.
. Planimetricmsips represent graphically physical features such as ‘
streams, lakes, roads, railroads, property and other boundaries.
A Egats are maps plotted from a plane survey having the third di-
mension omitted. They are used in the description of a tract of
land when it is not necessary to show relief, i.e. farm surveys
or a city plat. The first principle to be observed in the exe-
cution of this kind of drawing is simplicity. The information
should be clear, concise, and direct, The lettering should be
· done in a single stroke, and the north arrow and border be of the
simplest character. It is impractical to prepare a map containing
excess ornamentation which serves no useful purpose. The plat of
a survey should give clearly all the information necessary for the
legal description of the parcel of land. It should contain:
l. Lengths and bearings of all the sides,
2. Acreage.
5. Location and description of monuments found or set.
· 4. Location of highways, streams, etc.
5. Official division lines within the tract,
6. Names of owners of abutting property,
7. Title and north arrow.
8, Certification,
Sketches. The designer and inventor conceives his original idea
in the form of a mental picture, Preliminary sketches made of the
object as it was conceived preserve the idea. Later orthographic
design sketches are made. Pictorial sketches of an object or of
a detail of construction are more easily comprehended by a client
or workman than the orthographic projections. A difficult work-
O .
ing drawing is more easily understood if a pictorial sketch is
first made, Further this type of sketch is more easily and quickly
made. lt, however, does not treat the object in the same detail as
¤

 p 5.1.8
the orthographic sketch. Neither, as used by the engineer, is
intended to be a work of art but rather a record of information,
· · The requirement common to both is gopii proportion,
Charts, Graphs, and Diagrams. The graphical chart provides one
of the best methods for concise presentation of numerical data,
It assists clear thinking by eliminating the mental effort re-
quired in keeping in mind an involved series of figures. When
properly constructed and thoroughly understood, charts, graphs,
· and diagrams constitute an important aid for analysis of engineer-
ing data and the presentation of statistics for comparison or
· forecasting, When classified according to use, they may be divid-
ed roughly into two classes, those used for purely technical pur-
poses, and those for popular appeal in the presentation of inform-
ation or in advertising, The engineering draftsman is concerned
chiefly with the first class, but he should have some acquaint-
V ance with the preparation and possibilities of the second. The
ann here is to discuss briefly the types with which draftsmen
· should be familiar,
The construction of a graphical chart requires a fair de-
gree of draftsmanship, In engineering and scientific work the
important considerations are judgment as to the proper selection
of coordinates, accuracy in plotting points and drawing the graph,
and an understanding of the functions and limitations of the
chart,
The title is very important. Its wording should be studied
· until it is clear and concise. In every case it should contain
sufficient description to tell what the chart is, the source of
authority, the name of the maker, and the date it was made,
x

 Q Bol.9 `
Approved practice places the title at the top of the sheet
_ arranged symmetrically about a center line. If placed within the
· ruled space a border line or box will set it out from the sheet,
Each sheet of curves should have a title, When more than one
curve is shown on a sheet they should be drawn so as to be easily
l distinguishable, This may be done by varying the character of
the lines, using full, dotted, and dot-and-dash lines with a
tabular key for identification, or by lettering the names of the
curves directly along them. When not intended for reproduction
different colored inks may be used,
O   i
I
I

 5.2.l
CHAPTER 2
O
INSTRUMENTS AND MATERIAL
Instruments.-The draftsman is dependent for his success, to a certain
extent, upon the quality of the instruments and materials which he uses. As
a beginner, he will find that an inexpensive set of instruments will suffice
for his needs, but after he has become skilled it will be necessary for him
to secure instruments of better construction and finish so as to enable him
to do more accurate work.
In learning the use of drawing instruments particular attention should
· be paid to the correct methods of handling them. Read carefully the instruc-
tions given and observe strictly all the details of the technique. Bad form
in drawing is distressingly common and may be traced in almost every in-
stance to lack of care or knowledge at the beginning. This is the start of
bad habits, which when formed are most difficult to overcome. Learn to
hold the tools properly; take an easy, comfortable position at the drawing
· board; practice in a smooth uncramped style, trying to improve with each
lesson. It will be a revelation to the student when he realizes how easy
it is to draw. The secret is continued practice of the correct technique
in manipulation of tools. The two requirements are accuracy and spegd,
and in commercial work neither is worth much without the other. Accurate
pencil work is the first consideration. The beginner should learn that a
good drawing can be made just as quickly as a poor one. Erasing is expen-
sive and generally avoidable. The draftsman, of course erases an occasion-
al mistake and therefore should know methods of making erasures.
I
Drawing Beard.-The drawing board is usually made of well—seasoned and
straight-grained soft pine, the grain running lengthwise of the boani. Each
end of the board is protected by a side strip, 1-5/4 to 2 inches in width,
1

 5 Q2 Q2
V whose edge is made perfectly straight for accuracy in use of the T-square.
Frequently the end pieces are fastened by a glued, matched joint, nails, or
screws. Two cleats on the bottom, extending the entire width of the board,
O
will reduce the tendency to warp. Drawing boards are made in such sizes as
to accomodate the sizes of paper in general use. Large drawing boards are
usually mounted on specially designed horses or tables. Provision is made
for adjustment of the height of the board and for tilt to the size of the
drawing being prepared. Drawers may be included for storage of instruments
and supplies. Adjustable stools and foot rests may be used with this type
board, ·To clean a drawing beard art gum or wall paper cleaner is used.
Water is never used, because it may cause the board to warp. Remove the
· thumb tacks or scotch tape when through with the drawing board.
The drawing table should be set so that the light comes from the left
and adjusted to a convenient height for standing, that is, from 56 to 40
inches. (One may draw with more freedom standing than sitting). The board
should be inclined at a slope of about l to 8 inches. Table and instruments
should be dusted off before drawing begins.
· _T;$gE?£_e.·- The T-square is always used with the head on the left side
of the drawing board. An exception may be made in the case of a lefthanded
( person, whose table should be arranged with the light coming from the right
and the T—square used on the right edge. _
D Since the T—square blade is more rigid near the head than toward the
outer end, the paper, if much smaller than the board, should be placed close
to the left edge of the board (within about two inches or so) with its lower
edge several inches from the bottom, With the T—square against the left
edge of the board, square the top of the paper approximately. Hold in this
I
position, slipping the T—square down from the edge, and put a thumb tack or
scotch drafting tape in each upper corner. Tove the T—square down over the

 V 5.2.5
. paper to smooth out possible wrinkles and put thumb tacks or scotch drafting
tape in the other two corners. Scotch drafting tape is preferable because
_ it does not interfere with the use of the T-square.
· The primary use of the T-square is the drawing of parallel horizontal
lines. They should always be drawn from left to right. Consequently, points
for their location should be marked on the left side. Vertical lines are
drawn with the triangle set against the T-square, always with the perpendic-
ular edge nearest the head of the square and toward the light. These lines
are always drawn from bottom to tcp. Therefore their location points should
be made at the bottomq In drawing lines great care should be exercised in
keeping them accurately parallel to the T—square or triangle, holding the
• pencil point lightly but close against the edge, and not varying the angle
of the pencil during the progress of the line,
The T—square is manipulated by sliding the head along the left edge of
the board with the fingers against the end of the head. Adjustments are made
with the thumb above and the fingers touching the board, or oftener with the
_ fingers on the blade and the thumb on the board. In drawing vertical lines,
the T-square is held in position against the left edge of the board, the
O .
thumb on the blade, while the fingers of the left hand adjust the triangle.
One may be sure the T-aquare is in contact with the board by hearing the
little double click as they meet. I
Triangles.- Triangles are made of various substances, such as wood,
rubber, celluloid, and steel. `Wooden triangles are cheap but are likely to
warp out of shape. Those of rubber are frequently used and are in general
satisfactory. Celluloid triangles are extenseively used because of their
transparency, which enables the draftsman to see the work completed even
· when it is covered by the triangle. In using rubber or celluloid triangles
take care that it lies perfectly flat, or is hung up when not in use. When
n

 3.2.4
allowed to lie on the drawing board with a pencil or an eraser under one _
corner it will have a tendency to warp, especially if the room is hot or
E • the sun happens to strike the triangle. Triangles from 6 to 8 inches on
a side will be found convenient for most work, although there are many
cases where a small triangle measuring about 4 inches on a side will be
found useful. Every draftsman should have at least two triangles, one
having two angles of 45 degrees and one right angle, and the other having
angles of BO, 60, and 9C degrees respectively.
we have stated that vertical lines are drawn with the triangle set
against the T-square. Generally the 60-degree triangle is used because
,. it has the longer perpendicular. In both pcnciling and inking it is best
to use a triangle in contact with a guiding straight—edge. To insure
accuracy never work to the extreme corner of a triangle. The T-square
should be kept at least a half inch below the base line when in use with
triangles. Practice—exercises l through 4, Plate No. 3, by the use of
the T-square and triangle, using the dividers for measuring the spaces,
also see page 5.4.7 for instruction exercises, l and 2.
O
To test the accuracy of the 45-degree angles of a triangle, place the
triangle with the lower edge resting on the working edge of the T—square,
and draw a line. Now without moving the T-square place the triangle so
that the other 45—degree angle is in position occupied by the first. If
the two 45-degree angles coincide they are accurate. For various uses Qf
triangles see Plate No.l. For testing a triangle see Plate No. l, illus-
stration 3.
Lettering triangle.- The lettering triangle is an instrument used to
. space guide lines for freehand letters. It is similar in appearance to
other triangles with the exception that it has evenly spaced holes inserted
in the celluloid. In using the lettering triangle the edge is place against the

 5.2.5
‘ T—aquare and the pencil point is inserted in the holes. By sliding the
triangle, a guide line is made. The lines are always drawn from left to
• right without applying much pressure on the pencil. Too much pressure will
V cause the point to break and spoil the line. ·
T Scale: a rule graduated to a definite number of units to the inch and
T used to measure lines of a drawing in a predetermined ratio to the exact
i measurements of the object or area represented.
Q To represent objects, the full size of which are larger than can be
conveniently drawn, it is necessary to reduce the dimensions of the draw-
ing proportionately. For this purpose either the engineer’s or architect‘s
scale is used. These are made in several forms, the most convenient being
O-
the flat with beveled edges, and the triangular. They are of various
lengths, but that more commonly used is the l2 inch. The triangular scale
V has six surfaces on which are different graduations and the scales are
arranged so that the drawing may be made in any proportion to the actual
size. For mechanical work, the common divisions are multiples of 2; thus,
drawings are made run Size, é Size, e, 1/s, 1/16, 1/sz, 1/64, em. ir a
· drawing is   size, 5 inches is divided into 12 equal parts and each divi-
sion represents l inch. For architectural work the common division is a T
multiple of 2. lf a smaller division on a scale represents, for example,
l/l6 inch, the scale is said to read l/l6 inch. Scales are often divided
into l/l0, i/zo, l/30, L/40, l/50, l/60, etc., for use by civil engineers
and for measuring indicator cards, As far as possible successive measure-
ments on the same line should be made without shifting the scale. For
plotting and map drawing the civil engineer's scale of decimal parts, l0,
· 20, 50, 40, 50, 60, 80, 100 to the inch is used. This scale should never
be used for machine or structural work. The most important consideration
in drawing to scale is the thinking and speaking of each dimension in its
1

 5.2,5
full size and not in the reduced size as it appears on the drawing.
The scale should never be used as a substitute for the triangle_p£
• _ T-square in drawing lines.
Dividers
The dividers are instruments similar in appearance to the compass. f
Both legs are pointed and are straight and rigid. They have two primary ,
uses, dividing a line into parts and transferring dimensions from the scale.
Since they are basic instruments, ease in their use should be developed.
Adjustment
Dividers should be opened with one hand by pinching the
chamfer with the thumb and second finger. This will throw them into correct
I ""
position with the thumb and forefinger on the outside of the legs, the sec-
4 ond and third finger on the inside and the head resting just above the sec-
ond joint of the forefinger. It is thus under perfect control, with the
thumb and forefinger to close it and the other two to open it. This motion
should be practiced until an adjustment to the smallest fraction can be made.
ln coming down to small divisions, the second and third fingers must be
' gradually slipped out from between the legs while they are being closed.
Example in its Use
In bisecting a line the dividers are opened to an
estimated one—half of the length of the line, This distance is marked off
on the line, while holding the instrument by the handle with the thumb
and forefinger. lf the division is short, the leg should be moved out to
one·half the remainder, estimating by sight, but not removing the other leg
from its position on the paper. Then the line is spaced again with this
· setting. If this does not divide the line, the operation is repeated, until
the correct adjustment has been arrived at. ln like manner a line can be
divided into any number of equal parts.

 3,2.,7 ·
The proportional divider is a special instrument used in making re-
productions of drawings, at a different scale than the original. The
· needle points on one end of the instrument are set on the extreme ends
of the line to be reproduced. The distance between the needle points of
the other end is the correct proportion of the new scale, that is, the ’
exact distance.
Compass
The compass has the same general shape as the divider and is manip-
ulated in a similar way. It has several detachable parts, a pen part,
pencil part, and lengthening bar. First of all the needle peg of the
· ` compass should be adjusted so that the needle extends a trifle beyond the
pen point or pencil point. Insert the pen in place of the pencil leg.
Turn the needle adjustment nut and set it a trifle longer than the pen.
If the pencil leg is used, replace the pen leg. Sharpen the lead to a
long bevel and adjust it to the needle point.
P22
· To draw