Part 1

Transcriber’s Notes

Text printed in italics in the source document has been transcribed _between underscores_, bold face text =between equal signs=. Small capitals have been replaced with ALL CAPITALS.

More Transcriber’s Notes may be found at the end of this text.

SELF-HELP

MECHANICAL DRAWING

AN EDUCATIONAL TREATISE

“_LEARN TO DO A THING BY DOING IT._”--_OLD PROVERB_

SELF-HELP MECHANICAL DRAWING

_AN EDUCATIONAL TREATISE_

BY N. HAWKINS, M. E.

_Author of Handbook of Calculations, etc._

_New York_: THEO. AUDEL & CO., Publishers 1902

_Copyrighted by Theo. Audel & Co. New York 1902_

_This work is most kindly and respectfully dedicated to THE COMING MAN who at the present time is undoubtedly devoting a goodly share of his spare time to the study of drawing._

Preface.

_It is because of a personal and practical experience of the advantage to be gained by the possession of a knowledge of drawing, that the author is prompted to undertake the rather pleasant task of producing a self-help book relating to the subject._

_Since the days of youthful endeavor, the author has passed through an extended experience of mechanical life, and scarcely ever without chalk, pencil or instrument in hand, to illustrate by sketch or drawing, the tools to be employed, or to picture the finished product; accordingly, throughout this work, words of explanation and the drawings will go together to aid the diligent student._

_It has been said by an eminent writer, that “one workman is superior to another--other circumstances being the same--directly in proportion to his knowledge in drawing, and those who are ignorant of it must in many respects be subservient to others who have obtained that knowledge.”_

_It has been also said that no man is fitted to be foreman of a shop who cannot draw, and it is generally true that no one will be appointed to that position, except temporarily, who does not possess some knowledge of the art, either “freehand” or instrumental._

_It is a question how far a good working knowledge of drawing can be attained without a teacher; it is true that but few have become proficient without such aid, but it is equally true that “self-help” has been the key note to all advancement._

_The author received personal instruction in several ways and times, at home, in school, in an architect’s office, and under an experienced mechanical engineer, but it was in the early morning hours of a bright summer time--lang syne--that he made his first serious attempt to master the art of mechanical drawing. It was a struggle and a battle to hold himself down to “the board” to the finish, but it was a victory--one, won over slothfulness and impatience, and of such a nature as to warrant the use of the term “self-help” to the encouragement of others._

_In conclusion two sentiments may be added; if a good working knowledge of drawing is “worth the while” then, 1, the student should be thoroughly in earnest in acquiring it; 2, he should be willing to take sufficient time and give much hard study to gain the skill necessary for success._

_This persistence is not irksome. It carries its own reward, and the results are definite and sure._

“_One step and then another, and the longest walk is ended; One stitch and then another, and the largest rent is mended. One brick upon another, and the highest wall is made; One flake upon another, and the deepest snow is laid._”

Introduction.

Drawing is one of the arts; art relates to something to be done, and art in the industrial and mechanical sense aims chiefly at utility, and is governed by exact rules; hence mechanical drawing--so-called--tends first to be useful and helpful, and second to accuracy in execution, including most minute details; it aspires to the perfection of nature in adaptability of the means to the end.

Drawing constitutes a universal language, to acquire which is a matter of importance, for by its use one is able to illustrate the form and dimensions of an object, device, or utility, in very much less time, and far more clearly, than by a verbal description.

To a person who may not be able perfectly to understand the language of a country, to be able to draw is an aid and a safeguard; to use the words of Sir Joshua Reynolds, “the pencil speaks the language of every land.”

In extensive iron works and metal-working establishments the designer and draughtsman is always in demand. His services are indispensable and his position is a highly responsible one. It becomes his special province to design improvements, to furnish sketches and to make finished drawings; to calculate strains, strength, power, motion, weight, friction and durability. All this and much more is the professional draughtsman’s work.

In “directory” classification, he who accomplishes such comprehensive results as above described is termed a “Draughtsman,” but the word has as wide a meaning as “Engineer,” which takes in civil, mechanical, naval, sanitary, steam and other engineering specialists. So, in drafting, it includes the office boy employed in making blue prints, it embraces the copyists, tracers and assistants, as well as the head draughtsman and chief engineer.

Consequently the range is wide, and the line hard to draw between draughtsmen who work with their hands, and those who work with their brains. It may be added that the best men are too frequently undervalued, owing to the unavoidable difficulty in distinguishing the difference in true worth, between the two widely separated classes.

It may be remarked that they only draw well who draw intelligently; aptness in this, as in many other virtues, is a matter of slow growth, “here a line and there a line”--it’s the proper direction, not the rate of progress, that counts in the end.

There are several methods of drawing--1, Free-hand; 2, Instrumental; 3, Geometrical; 4. Perspective. In the first the work, also termed sketching, is executed by pencil, pen, crayon, or even paint-brush; in the second the result is attained by the use of rule, tee-square, drawing pen, etc.; this method is also denominated mechanical drawing, and suggests the title of this volume.

The great usefulness, not to say necessity, of readiness in executing accurately, drawings “to scale,” is emphasized by the fact that now, more than ever, is all machinery designed, and it may almost be said, is “built,” in the draughting room--this is a valuable hint relating to “reading” drawings.

It is wise, as well as easy, to begin at the beginning of things; thus, it is altogether the good part to mount a ladder by the first and second rounds rather than to attempt it by taking the third, sixth, ninth, etc.--especially are first and second rounds the very best to start upon; “Chalk-work,” is the first subject introduced, next, that of “Free-hand.” These are the first steps leading upward in this most agreeable attainment--skill in illustrating and designing of objects, tools, and utilities.

A single word of advice before introducing the elementary work connected with mechanical drawing: if the student should experience difficulty in mastering the diagrams and curves abounding in this book, let him consult an experienced draughtsman or teacher, who, by a few strokes of a lead pencil, can easily make them plain; that knowledge--which cannot be printed or self-taught--termed _the Craftsman’s Art_, is communicated largely by personal telling and showing, from man to man; in drawing, this help should be thankfully availed of, when necessity arises.

NOTE.--Sketching is often in demand because there is no time for finished or careful drawings, and the one who can draw a few lines in a moment to let a sudden necessity be known, is the man of the hour. All candidates for First Class Engineer’s Certificates in marine service in the navy have to undergo an examination in rough drawing; this is intended not so much as a proof of the applicant possessing the capability of a draughtsman, but in the event of any injury to the engines in his charge, so that he may be able to send to his Superintendent a rough drawing of the particular part, properly dimensioned, so that it could be worked from, and time saved on the arrival of the ship at the port where the repairs are to be done.

“_No matter how thorough our education may have been at the first, rules and formulas will slip from the memory, and every day’s experience gives additional evidence of the truth of the old adage that_ ‘THE KEY THAT RESTS, RUSTS.’”--SIMPSON BALLARD.

The Plan of the Work.

The purpose or scope of this work may be briefly stated: It is to aid the aspiring student in making the first advance towards a thorough and useful knowledge of drawing in its several divisions, as elsewhere defined.

The method to be followed in presenting the subject will be the natural order clearly and simply defined, as “from the less to the greater.”

The first subject to be discussed comes under the heading of chalk-work, _i. e._, such drawings as can be executed on a blackboard, a floor, or even on more primitive surfaces, such as a smooth stone or board.

This is indeed a lowly beginning, but the author is quite confident it will awaken as much interest as any part of the book--even in the most experienced in the art of drawing, as to them it will revive the ambitions and first crude attempts made in the golden days of their youth.

Let it be clearly understood by all, and especially by those who wish to learn drawing, that the study of this delightful art does not require any special qualification. We need only ask one question: Have you learned to write? If so, be assured you may learn to draw, but to all the same rule applies, first the elements of the art, and afterwards the more advanced study.

It is not expected that all should exhibit a decided taste for drawing, for the possession of this is rather a gift of nature than the result of education; but a knowledge of principles and a certain amount of executive ability may be obtained by every one of average capacity, and whatever the natural power may be, it will be increased and developed by exercise; if the progress is steady and continuous and in the right direction, success is sure to crown the work.

The second division of the book will be free-hand drawing, _i. e._, that which is executed without instruments. Nothing to instruct has been spared in this important step in the path of advancement.

The illustrations accompanying the two opening sections have been made designedly elementary, for there are many who have a taste for drawing and who have a desire to learn, who from place of residence or other circumstances have not the opportunity of receiving the assistance of a master. To such this book presents itself as a friend directing to the right road, talking, reasoning, and explaining by the way.

The “chalk-work” and “free-hand” sections of the book relate to the foundations upon which all must rest who seek the aid to be derived from the art; hence, the following pages are written with a view to encourage all, and those who are prepared to follow the directions given in them may look forward to the possession of sufficient drawing power to add to their usefulness in after life.

At this point of attainment there arises a need to know the meaning of many words and phrases used by draughtsmen; these are grouped alphabetically from A to Z under the heading of,----

Useful Terms and Definitions: Memorizing these few pages will be of benefit, as an intimate knowledge of the language of the drawing office stamps a man as worthy of a hearing, and assures attention to anything which he may write or say pertaining to the art.

After the Definitions the subject explained will be the Instruments and Materials used in mechanical drawings; following in due course appear Geometrical and Mechanical Drawing, Gearing, Linear Perspective, Projection, Shading, Tracing, Lettering, Drawing Office Rules, Reading Drawings, Useful Tables and a General Index, to which the student is referred. A careful reading is requested to the following helpful note.

Grateful acknowledgment is made to George Perrott, Esq., M. E., for practical and technical assistance throughout the work, and to Theo. Lucas, Engineer, for text and illustrations in the portions of the book relating to Linear Perspective and Projection.

NOTE.--In MACHINERY Prof. Chas. H. Benjamin says, referring to drawing, under heading “How and what to study,” “... I have so far said nothing about drawing, for I do not think it of much use to learn that, until you know what you want of it. All this time that you have been studying mechanism you should have had a sketch book or pad of note paper, and made free hand sketches of mechanical movements which interested you and of various machine details. You should accustom yourself to use drawing as a means of expressing ideas, just as you use written words, so that it becomes a second nature to you to sketch anything you wish to remember or describe. If you work from blue-prints in the shop, or if you can borrow some to study, this will help you to understand how a drawing is made. You can get some drawing instruments at any time and begin to practice on drawing straight lines and circles, so as to become familiar with the instruments. And here it will be of great benefit to you if you can attend an evening drawing school for one night in the week at least.

“When you have become sufficiently familiar with the principles of drawing, a book on mechanism will tell you how to draw gear teeth and cams, and how to design various link motions. Make up your own problems from what you see in the shop and make your drawing a means to an end and not the principal thing; it is of little use to be able to make a nice drawing unless you know what to draw and why.

“Drawing is a convenient tool as an aid in expressing to others the ideas which you wish to convey; in all cases take the problems and the ideas from your every-day work and that which is around you; your success will depend upon the close connection which you keep at all times between your acquired knowledge and your practical work.”

General List of Contents.

INTRODUCTION, 1-24

CHALK WORK, 25-38

PRELIMINARY TERMS AND DEFINITIONS, 39-52

FREEHAND DRAWING, 53-78

GEOMETRICAL DRAWING, 79-100

DRAWING MATERIALS AND INSTRUMENTS, 101-134

MECHANICAL DRAWING, 135-188

PENCILING, 139-147

PROJECTION, 148-164

INKING IN DRAWINGS, 167-170

LETTERING DRAWINGS, 171-175

DIMENSIONING DRAWINGS, 176-179

SHADING DRAWINGS, 180-181

SECTION LINING AND COLORS, 182-185

REPRODUCING DRAWINGS, 186-188

DRAWING OFFICE RULES, 189-195

GEARING, 197-208

DESIGNING GEARS, 209-216

WORKING DRAWINGS, 219-227

READING WORKING DRAWINGS, 228-230

PATENT OFFICE RULES FOR DRAWINGS, 231-236

USEFUL HINTS AND “POINTS,” 237-244

LINEAR PERSPECTIVE, 245-265

PERSONAL, BY THE EDITOR, 281

USEFUL TABLES, 269-280

REFERENCE INDEX, 283

The peculiarity of all art is that it cannot be communicated in writing alone, craft is a term which is synonymous with art; a craft requires manual dexterity which cannot be taught in books.

Chalk Work.

The blackboard has been well called the great weapon of the modern educator; this is especially true in reference to instruction in an art dealing with lines, curves and figures.

Many a man can chalk out on a blackboard, or on a piece of sheet-iron, or on the floor, just what he wants to show, and make his meaning very plain; hence, in every workshop, and many other places, a blackboard is more than useful, and it has been said that no draughting office is complete without one.

Fig. 6 represents a chalk-crayon.

Figs. 7 and 8 need no explanation, as they represent two forms of the well-known blackboard.

Chalk lines have this advantage--they are easily altered or rubbed out when not needed any longer. The work executed upon a blackboard is mostly done by hand, without aid from instruments; a few tools, however, are useful--such as, 1, large wooden blackboard compasses holding a crayon, which are made and sold by the trade in size twelve inches to thirty inches in length; 2, a straight-edge; and 3, some crayons. With the compasses circles and part of the circle can be made, and with the straight-edge the larger lines can be drawn.

These instruments are shown on page 29, and are, 1, compasses, for holding chalk for making circles; 2, a tee-square; 3, a straight-edge; 4, a protractor for measuring angles; 5, a triangle 60° and 30°; 6, a brass holder for crayons.

Blackboard Drawing.--The use of a blackboard comes principally and properly under the head of free-hand drawing, but its importance is such that a separate division of the volume is assigned to it.

Thus, chalk-work may be considered the first lesson in “free-hand,” as all the examples can also be most profitably practiced with pencil and paper.

Very rapid drawing upon the board should not be encouraged, as it is likely not to be accurate enough; again, the board should be entirely free from grease. Cloths, sponges or chamois skin rubbers may be used to erase or change the chalk marks. Vertical lines should be drawn from above downward; short lines should be drawn with the fingers alone, those somewhat longer with the hand, using the wrist-joint; the still longer lines with the forearm, using the elbow-joint; those longer yet with the whole arm, using the shoulder-joint; lines should always be drawn with a uniform motion, slow enough for the eye to follow.

Practice in chalk-work should alternate with sketching in a sketchbook and with geometrical drawing--to be hereafter described. The student should practice a short time on the board, at least once a week; large sizes are the most profitable for the representations to be made; when drawing in different directions the hand should be turned, not the paper or board; the hand should never be allowed to obstruct the sight, hence the hand and fingers should be held in a position of freedom--with fingers not nearer than 1¹⁄₂ or 2 inches from the board.

NOTE.--The first lesson of any kind the author received in drawing was to make a straight line; this was effected by holding the pencil nearly erect and guiding it along by the aid of the little finger held pressed against the edge of a board; this was a useful item of knowledge, as proved by passing years.

A well-known artist, in telling his early experience, said: “The first thing I was taught was to draw a line, divide it, erect a perpendicular from its center, and afterwards to divide the angle made by the perpendicular.” In answer to a question asking how long he was kept at the lines, he replied, “about two months--or a month or two,” indicating that even the longer time would have been well spent in learning to draw a straight line.

PREPARATORY PRACTICE IN DRAWING.

Every visible object is bounded by lines which enable the observer to determine its shape. If these lines are straight or curved, the shape of the object is regular; if broken, the shape of the object is irregular.

The elements, then, of form are lines, straight, curved, or broken, and these, therefore, furnish the beginning of all instruction in free-hand or mechanical drawing.

PERPENDICULAR LINES.

Fig. 15 shows six lines--upright and perpendicular, with points or “dots” indicated at the top and bottom of each line; to draw these, proceed thus:

The learner should stand with his right shoulder opposite the board, and the weight of the hand and the arm should be allowed to fall naturally; now, make on the board two points, one being six inches above the other, these being merely “dots,” shown at the ends of the lines, figs. 15, etc., and made with two motions; the line between the points should now be drawn not too quickly from the upper to the lower point; three movements of the hand and arm complete the line; to draw the other five lines the movements have simply to be repeated.

If the student pronounces to himself “one,” “two,” “three,” at each motion, it will be helpful; in this exercise, fig. 15, the aim is to make six lines, each line being parallel to the first. Again, in the example, it is intended that the lower point should be made first, next the upper, and lastly the line drawn from the upper to the lower point, but the order may be reversed; at _one_ the upper point, at _two_ the lower, at _three_ the stroke upwards to complete the line.

HORIZONTAL LINES.

To make these as shown in fig. 16, proceed as follows: With the word _one_ make a point, with _two_ another point six inches at the left, with _three_ draw a straight line from the left point to the right. All added lines should be parallel: for practice, reverse the process thus, _one_, make a “point,” at _two_ another point at the right, at _three_ draw line to the left.

The student will note that the two motions--at the words _one_ and _two_--are to fix the positions of the ends of the lines; this practice will be found useful in the most advanced examples and an item of elementary practice never to be forgotten--like the help to be derived by the first round of a ladder.

OBLIQUE LINES.

In drawing oblique straight lines as shown in fig. 17, at the word _one_ let the student make the lower point; at the word _two_ the upper, a little to the right of the lower; at the word _three_ draw a line quickly from the upper to the lower point. In pronouncing the words _one_, _two_, _three_, let the student make the additional parallel lines.

As shown in fig. 18, at the word _one_ make the lower point; at the word _two_ the upper point, a little _to the left_; at the word _three_ draw a line rapidly from the upper to the lower point, and “timing” the process by repeating _one_, _two_, _three_, make the additional parallel lines.

BROKEN LINES.

A broken line is composed of two or more straight lines at angles to each other (see fig. 19). To draw them begin (saying) _one_, make a point; _two_ a point below at the left; _three_, a point above at the left; _four_, draw a line from the left hand point to the lower point; at the word _five_, from the lower point to the upper right hand point. For practice draw numerous lines in the same way, keeping them parallel to each other, as shown in fig. 20.