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Search the Wayback Machine Search icon An illustration of a magnifying glass. Sign up for free Log in. Technical drawing Item Preview. EMBED for wordpress. Want more? Advanced embedding details, examples, and help! Another method draftsman’s stapler. Tracing paper should not be fastened directly upon the board because small imperfections in the surface of the board will interfere with the line work.

Always fasten a larger backing sheet of heavy white drawing paper on the board the drawing over this sheet. Drawing pencils are hexagonal in shape to fit between the thumb, forefinger, and second finger, and to prevent them from rolling off the. The softer grades right are used for technical sketching, for lettering, arrowheads, and other freedrawing. The H and 2H pencils are widely used on pencil tracings for blueprinting.

These pencils are too soft to be useful in mechanical drafting. Their use for such work results in smudged, rough lines which are hard to.

These grades are used for art work of various kinds, and for full-size details in architectural drawing. In the long run, the total expense for mechanical pencils is probably less than for wooden pencils. A new type of mechanical pencil has been introduced which uses flat leads. Lines of uniform width suitable for visible or hidden lines may be drawn without the necessity of ever sharpening the lead.

In drawing a line, the flat face of the lead is held against the ruling edge. Pencil holders are also available, Fig. Unfortunately the pencil industry has not Choice of Grade of Pencil. Thus, an F lead by one manufacturer actually may be about the same as a 2H of another manufacturer. Generally speaking, the Koh-i-noor, Mars, and Castell pencils appear to be a grade or two harder than the other makes. Therefore, it is necessary for the draftsman to select the brand he likes and then experiment with the various grades of lead.

He must first know the character of line required and be able to tell at once by inspection whether or not a line is correct in. To begin with, the type of drawing must be taken into consideration. For light construction lines, guide lines for lettering, and for accurate geometrical constructions or any work where accuracy is of prime importance, use a hard pencil, such.

For mechanical drawings on drawing paper or tracing paper, the lines should be black, particularly for tracings to be reproduced as blueprints or otherwise. The pencil chosen must be soft enough to produce jet-black lines, but hard enough not to smudge too easily or permit the point to crumble under normal pressure.

This pencil will vary from F to 2H, roughly, depending upon the paper and weather conditions. The same comparatively soft pencil is preferred for lettering and arrowheads.

Another factor to consider is the texture of the paper. If the paper is hard and has a decided “tooth,” it will be necessary generally to use harder leads.

For smoother surfaces, softer leads can be used. Hence, to obtain dense black lines, the paper should not have too much “tooth. On humid days the paper absorbs moisture from the atmosphere and becomes soft. This can be recognized because the paper expands and becomes wrinkled. It is necessary to select softer leads to offset the softening of the paper. If you have been using an F lead, change to an HB until.

Sharpening the Pencil. A dull pencil produces fuzzy, sloppy, indefinite lines and is the mark of a dull and careless student. Only a sharp pencil is capable of producing clean-cut black lines that sparkle with clarity. Sharpen the unlettered end of the pencil, Fig. First, cut away the wood with a sharp knife, starting about I5″ from the end, and leaving about f” of lead uncut, Fig.

Or use a simple pencil sharpener, Fig. Then shape the lead to a sharp conical point on a pencil pointer sandpaper pad or a small file , Figs. Never sharpen your pencil over the drawing or any of your equipment.

Many draftsmen then “burnish” the point on a piece of hard paper to obtain a smoother, sharper. Keep the sandpaper pad, when not in use, in a container, such an envelope with one end cut open, Fig. For straight-line drawing, some draftsmen prefer the wedge point, Fig.

This point is produced by cutting the wood away as at a or b , and then sharpening on opposite sides, as shown at d. In drawing a line with this point, the flat face. Some prefer to sharpen slightly on the edges of the wedge so as to produce a “screwdriver” point, as shown. If pronounced. A quick method of making a good wedge point is to produce first a conical point and then cut a flat face on one side.

The resulting point is elliptical in contour, Fig. Conventional Lines. Each line on a techdrawing has a definite meaning and is drawn in a certain way. The conventional lines adopted by the American Standards Association are shown in Fig. There should be a distinct contrast in thicknesses of different kinds of lines, particularly. Pencil leads should be hard enough to prevent smudging, but soft enough to produce dense-black lines of best reproducing quality.

In Fig. It would be well to measure the first few hidden dashes and center -line dashes you make, and then thereafter to estimate the lengths carefully by eye.

Note that the thick and medium ink lines are considerably wider than the corresponding pencil lines, while the thin lines are about the same width in pencil or in ink. For inking procedures, see Erasers are available in many degrees of hardness and abrasive These erasers are used for erasing either pencil or ink.

Avoid gritty erasers, even for erasing ink, as they invariably damage the paper. Best results are obtained if a hard surface, such as a triangle, is placed under the paper being erased. If the surface has become badly “grooved” by the lines, the surface can be improved by burnishing with a hard.

The erasing shield, Fig. The electric erasing machine, Fig. Keeping Drawings Clean. Cleanliness in draftvery important and should become a habit. Cleanliness does not just “happen” it results only from a conscious effort to observe correct procedures. First, the draftsman should keep his hands clean at all times.

Oily or perspiring hands should be frequently washed with soap and water. Talcum powder on the hands tends to counteract excessive perspiration. Second, all drafting equipment, such as drawing board, T-square, triangles, and scale, should be wiped frequently with a clean cloth.

Water should be used sparingly and dried off immediately. Artgum or other soft erasers may also be used for cleaning. Third, the largest contributing factor to dirty drawings is not dirt, but graphite from the pencil; hence the draftsman should observe the following precautions: 1 Never sharpen a pencil over the drawing or any equipment.

Always wipe the pencil point with a clean cloth, after sharpening or pointing, to remove small particles of loose graphite. Never place the sandpaper pad in contact with any other drawing equipment it is completely enclosed in an envelope or similar cover, Fig. Never work with the sleeves or hands resting upon a penciled area. Keep such. Avoid sliding anything across the drawing.

A certain amount of sliding of T-square and triangles is necessary, but this can be minimized if triangles are picked up by their tips and the T-square blade tilted upward slightly before moving. Never rub across the drawing with the palm of the hand to remove eraser particles; use a dust brush, Fig.

The practice of making a pencil drawing, scrubbing it with artgum, and then retracing the lines, is poor technique and a waste of time, rules. At the end of the period or of the day’s work, the drawing should be covered protect it from dust. Lean the pencil in the direction of the line at an angle of approximately 60 with the paper, b , and draw the line from left to right. Keep the pencil in a vertical plane, b. In general, reverse the above procedure.

Place the T-square head. Triangles and T-squares, especially when new, often have very sharp edges which tend to cut into the pencil lead and cause a trail of graphite to be distributed along the line. To prevent smearing of these particles, blow them off at intervals. If the edges of the triangles or T-square are too sharp, they can be sanded very lightly with 00 sandpaper just enough to remove the sharp edges.

Place the triangle on as shown in Fig. With the left hand,. Then draw the line upward, rotating the pencil slowly between the thumb and forefinger. Lean the pencil in the direction of the line at an angle of approximately 60 with the paper and in a vertical plane, b.

Meanwhile, the upper part of the body should be twisted to the right, as shown at c. Place the T-square head Left-Handers. In this case, the line would be drawn downward. Most inclined lines in mechanical drawing are drawn at The Triangles. The triangles. Testing and Correcting the Triangles. Triangles are subject to warping, sometimes even before they are sold by the dealer. Therefore, the purchaser should test his new triangles immediately after purchase to determine if they are “true.

Test the sides of the triangles for straightness in the If the two lines thus drawn do not coincide, the right angle is not 90 and the error is half the angle between the two lines. If the two lines do not coincide, there is an error in one or both 45 angles. A direct test of the 45 angle can be made by drawing a right triangle.

The sides adjacent to the 90 angle will be equal if the two 45 angles are correct assuming the 90 angle to be correct. To test the 60 angle of the 30 X 60 triangle, draw an equilateral triangle, as shown at c. If the sides are not exactly equal in length, the 60 angle is incorrect. Another method of testing the 60 angle, d , is to draw a horizontal line AB slightly. When the triangle is placed as shown, its hypotenuse should pass through C.

To true up the edge of a triangle, make a “rough cut” by scraping the edge with a knife or with a scraper, Fig. Or place the triangle in a vise and plane with a sharp block plane set for a very shallow cut. Then hold Triangle, the triangle flat against the edge of a table top, with the secting at C. The positions of the triangles for drawing lines at all of shown in Fig. In the figure it is understood that the triare resting upon the blade of the T-square. Thus, it is possible.

Note carefully the directions for drawing the lines, as indicated by the arrows. Note that all arrows in the left half point toward the center, while those in the. For measuring or setting off angles other than those obtainable with the triangles, the protractor is used.

The best protractors are made of nickel silver. Drafting Angles. The Draft-Scale-Angle, a , is a practical drafting aid whose applications are apparent in the figure. Obviously any straightedge, such as one of the triangles, may be substituted for the T-square in this operation, as shown at a. To draw perpendicular lines when one of the lines makes 15 with horizontal, ;.

Lines at 30, 60, or 45 with Given Line. To draw a line making 30 with a given line, arrange the triangle as shown in Fig. Angles of 60 and 45 may be drawn in a similar manner. A drawing of an object may be the same size as the object full be larger or smaller than the object; in most cases, if not drawn lull size, the drawing is made smaller than the object represented.

The ratio of reduction depends upon the relative sizes of the object and of the sheet of paper upon which Given Line. The triangular have the advantage of combining many scales on one stick, but the user will.

The almost universally used by professional draftsmen because of its convenience, but several flat scales are necessary to replace one triangular scale, and the total cost is greater.

Since machine drawings are made full, half, quarter, and eighth size, these scales may be obtained on one or two flat scales of the type shown in Fig. The architects scale is intended primarily for Architects Scale.

The full-size scale is also useful in drawing relatively small objects, and for that reason the architects scale has rather. The architects scale has one full-size scale and ten overlapping reduced-size By means of these scales a drawing may be made to various sizes from full. Full Size. Each division in the full-size scale is ts”. Each inch is divided first into halves, then quarters, eighths, and finally sixteenths, the division lines diminishing in length with each division.

Half Size. Use the 3-inch scale in which 3″ equals 1 ‘. The subdivided portion to the left of zero represents one foot, and is divided into inches, then half inches, quarter inches, and finally eighth inches. The entire portion repre;. To set off 10J”, read off 9″ from zero to the left, then add 1 ” and set off the total 10 “, as.

Eighth Size. The subdivided portion to the right of zero represents 1 ‘, and is divided into inches, then half inches, and finally quarter inches. The entire portion, representing 1’, actually is H”; therefore: If” equals.

Use the full-size scale, and multiply every dimension mentally by Double Size-. Similarly, the tV’ scale can be used to set off sixty-fourths of an inch full size, since each small. Do not abuse the scale by using it as a straightedge, hammering thumbtacks with it,. Engineers Scale. The engineers scale is graduated in the decimal is also frequently called the civil engineers scale because it was originally used mainly in civil engineering. The name chain scale also persists because it was.

The engineers scale is especially suitable for map drawing, because when a tract of land is surveyed, distances are measured with a flexible steel tape graduated in feet and tenths of a foot. The engineers scale is graduated in units of one inch divided into 10, 20, 30, 40, 50, and 60 parts. The engineers scale is also convenient in machine drawing to set off dimensions expressed in decimals. For example, to set off 1. To set off the same dimension half size, use the “scale,” b , since the “scale’.

The objects represented in Mechanical Draftsmans Scale. For this. To make a drawing of an object to a scale of size, for example, use the mechanical draftsmans scale marked j size, which is graduated so that every j inch represents 1 inch. Thus, the j-size scale is simply a full-size. These scales are also very useful in dividing dimensions. For example, to draw a 3×6″ dia. Instead of using arithmetic to find half of 3H”, it is easier to set off 3H” on the half-size scale.

Triangular combination scales are available which include the full and half-size mechanical draftsmans scales, several architects scales, and an engineers scale.

The increasing use of decimal dimensions has Decimal Scale. The complete decimal system of dimensioning, in which this scale is used, is ;. To Indicate the Scale on a Drawing. For examples. For drawings of buildings, piping, and other structures in which the dimensions are in feet and inches, the architects scales should be given in terms of inches to feet,. Accurate drafting depends considerably upon Accurate Measurements. Do not take measurements directly off the scale with the dividers or compass, as damage will result to the scale.

Place the scale. If extreme accuracy is required, a tiny prick mark may be made at the required point with the needle point or stylus, as shown at b , or with one leg of the dividers. Avoid cumulative errors in the use of the scale. If a number of distances are to be set off end-to-end, all should be set off at one setting of the scale by adding each successive measurement to the preceding one, if possible. Avoid setting off the distances individually by moving the scale to a new position each time, since slight errors in the measurements may accumulate and give rise to a large error.

Drawing instruments are generally sold in “sets,” in be purchased separately. The principal parts of.

Tool steel is used for the blades of ruling pens, for spring parts, for divider points, and for the various sion-resistant,. For the student or the professional draftsman it is advisable, and in the end more economical, to purchase the best instruments that can be afforded.

Good instruments will satisfy the most rigid requirements, and the satisfaction, saving in time, and improved quality of work which good instruments can produce will more than justify.

Unfortunately, the qualities of high-grade instruments are not likely to be recognized by the beginner, who is not familiar with the performance characteristics required and who is apt to be attracted by elaborate sets containing a large number of shiny low-quality instruments.

Therefore, the student should obtain the advice of his drafting instructor, of an experienced draftsman, or of a reliable dealer. Formerly it was general practice to make pencil drawings make an inked tracing from it on tracing cloth. As reproduction methods and transparent tracing papers were improved, it was found that a great deal of time could be saved by making drawings directly in pencil with dense black lines on the tracing paper and making prints therefrom, thus doing away with the preliminary pencil drawing on detail paper.

Today, though inked tracings are made when a fine appearance is necessary and where the greater cost is justified, the overwhelming proportion of drawings are made directly in pencil on tracing These developments have brought about the present “giant-bow” sets which are now by all the major manufacturers, Fig.

The large bow instrument is much sturdier and is capable of taking the heavy pressure necessary to produce dense black lines. Most of the large bows are of the center-wheel type, Fig. Several manu-. The friction in the pivot joint is sufficient to hold a setting except when the pressure must be very heavy and the radius large. In that case the compass can be rigidly locked in position. The Compass. A typical old-style compass is shown in Fig. All such instruments have a socket joint in one leg which permits the insertion of either pencil or pen attachments.

A lengthening bar, b , is used to increase the radius. This type of compass is excellent for drafting where it is not necessary to exert great pressure in order to produce heavy dark lines.

For production drafting, in which it is necessary to. Using the Compass. These instructions apply generally both to the oldand the giant bow compasses. The compass, with pencil and inking attachments, is used for drawing circles of approximately 1″ radius or larger, Fig. Most compass needle-points have a plain end for use when the compass is converted into dividers, and a “shoulder-end” for use as a compass.

Adjust the needle point with the shoulderend out and so that the small point extends slightly farther than the pencil lead or pen nibs, Fig. To draw a penciled circle, Fig. Any error in radius will result in a doubled error in diameter; hence, it is best draw a trial circle first on scrap paper or on the backing sheet and then check.

Manipulate the compass with one hand, as shown for handling the dividers in Fig. On drawings having circular arcs and tangent straight lines, draw the arcs first, whether in pencil or in ink, as it is much easier to connect a straight line to an arc than the reverse. For very large circles, use the lengthening bar to increase the compass radius. Use both hands, as shown in Fig. For required lines, the arcs and circles must be black, and softer leads must be used. However, since heavy pressure cannot be exerted on the.

For example, if an F pencil is used for visible lines drawn with the pencil, then an HB might be found suitable for the compass work. In summary, use compass leads that will produce arcs and circles that match the regular pencil lines.

It is necessary to exert pressure on the compass to produce heavy “printable” circles, and this tends to enlarge the compass center hole in the paper, especially if. In such cases, use a horn center or “center tack” in the hole, and place the needle point in the hole in the tack.

Sharpening the Compass Lead. Various forms of compass lead points are At a a single elliptical face has been formed by rubbing on the sandpaper pad, as shown in Fig. At b the point is narrowed by small side cuts. At c two long cuts and two small side cuts have been made so as to produce In using the compass, never use the plain end or the needle point. Instead, use the shoulder-end as shown in Fig. Usually all of the compass leads provided in drawing sets are hard.

Softer leads are readily available if you use a mechanical pencil, Fig. Otherwise, Fig. Avoid using leads that are too short to be sharpened as shown in Fig. Besides steel points, pencil and pen attachments arc provided. The “beams” may be made of nickel silver, steel, or wood, and are procurable in various lengths. The pivot joint should be loose enough to permit easy manipulation with one hand, as shown in Fig.

If the pivot joint is too tight, the legs of the. Most dividers are provided with a “hair spring” so that minute adjustments can. The dividers are used for spaces of approxior more. For less than 1″ spaces, use the bow dividers, Fig. Never use. Adjust the dividers with the fingers of the hand that holds them, to the approximate unit of division, estimated by eye.

Rotate the dividers counterclockwise through , and then clockwise through , and so on, until. If the last prick of the dividers short of the end of the line to be divided, increase the distance between the divider points proportionately. For example, to divide the line AB, Fig. When it is found that the trial radius is too small, the distance between the divider points is increased by one-third the remaining distance. If the last prick of the dividers. To set off a large number of equal divisions, say 15, first set off 3 equal large divisions and then divide each into 5 equal parts.

Wherever possible in such cases, use the scale instead of the dividers, as described in 41, or set off the total and then divide into the parts by means of is. For this purpose, points of division are marked on the instrument so as to secure the required subdivisions readily.

Some instruments are calibrated to obtain special ratios,. The Bow Instruments. The bow instruments are classified as the bow dividbow pen, and bow pencil, Fig.

Except for the handles and thumbscrews, the. There are two general types, the side-wheel bows, Fig. Fine instruments are available in both styles, and hence the choice is purely a matter of personal preference. Using the Bow Instruments. The bow pencil is used for drawing penciled having a radius of approximately 1″ or smaller.

Whether the center-wheel instrument or the side-wheel instrument is used, the adjustment should be made with the fingers of the hand that holds the instrument, Fig.

When adjustment of any of the side-screw bow instruments must be made directly from a large to a small radius, or vice-versa, it is best to press the two legs together with the fingers of the left hand, c , thus relieving the pressure upon the thumbscrew, so that it may be spun to position quickly and without unnecessary wear upon the threads. The lead is sharpened in the same manner as for the large compass, 46, except that for small radii, the inclined cut may be turned inside if preferred, Fig.

For general use, the lead should be turned to the outside, as shown at b. In either case, always keep the compass lead sharpened. Avoid stubby compass leads, which cannot be properly sharpened.

In adjusting the needle point of the bow pencil or bow pen, be sure to have the needle extending slightly longer than the pen or lead, Fig. In drawing small circles, greater care is necessary in sharpening and adjusting the lead and the needle point, and especially in accurately setting the desired radius. The bow dividers are used for the same purposes as the large dividers, but for smaller approximately 1″ or less spaces and more accurate work.

Always use the bow dividers in preference to the large dividers, if the spacings are within the range of the. To use the instrument, hold the knurled head of the tube between the thumb and second ringer, placing the first finger on top of the knurled head of the pin. Place the point of the pin at the desired center, lower the pen or.

To Lay Out a Sheet. After the sheet has been attached to the board, as explained in 17, proceed as follows: I. Using the T-square, draw a horizontal trim line near the lower edge of the paper; and then using the triangle, draw a vertical trim line near the left edge of the paper.

Both should be light construction lines. Place the scale along the lower trim line with the full-size scale up. Draw short light dashes perpendicular to the scale at the required distances. See Fig. Place the scale along the left trim line with the full-size scale to the left, and mark the required distances with short light dashes perpendicular to the scale. Draw horizontal construction lines with the aid of the T-square through the. Retrace the border and the title strip to make them.

Technique of Pencil Drawing. By far the greater part of commercial drafting is executed in pencil. Most prints are made from pencil tracings, and all ink tracings must be preceded by pencil drawings.

It should therefore be evident that skill in drafting chiefly implies skill in pencil drawing. Drafting supply houses can supply such papers, printed to order, to schools for little or no extra cost. Dark Accented Lines. The pencil lines of a finished pencil drawing or tracing should be very 1. Ends by a little extra pressure on the pencil, a.

Curves should be as dark as other lines, b. Hidden-line dashes and centerto give. Dimension lines, extension lines, section lines, and center lines also should be dark. The difference between these lines and visible lines is mostly in.

A simple way to determine whether your lines on tracing paper or cloth are dense black is to hold the tracing up to the light, Fig. Lines that are not opaque will not print clearly by blueprinting or otherwise. Contrast in pencil lines should be similar to that of ink lines; that is, the difference between the various “weights” should be mostly in the width of the line, with little if any difference in the degree of darkness, Fig.

The visible lines should contrast strongly with the thin lines of the drawing. If necessary, draw over a visible line several times to get the desired thickness and darkness. A short retracing stroke backwards to the left , producing a “jabbing” action, results in a darker line. While some pencil of a drawing placed underneath the tracing paper usually when a great deal of erasing and changing is necessary on the original drawing , most drawings today are made In making a drawing directly on tracing paper, vellum, or cloth, a stiff smooth sheet of heavy white drawing paper should be placed underneath.

Such a sheet is known as a backing sheet. The whiteness of the backing sheet improves the visibility of the lines, and the hardness of the surface makes it possible to exert pressure on the pencil and produce dense black lines without excessive grooving of the paper. These “tracings,” or drawings, are intended to be reproduced by blueprinting or by other kindred processes, Chapter 29, and.

The ruling pen. Ruling Pens. The nibs should be sharp, but not sharp enough to cut the paper. See 63 for sharpening the ruling pen. Various devices have been devised to permit the blades to open for easy cleaning, as. Thickened ink be thinned by adding a few drops of a solution of four parts of aqua ammonia. Drawing ink, Fig. The fine particles of carbon give the deep, black luster ink, and the gum makes it waterproof and quick to dry. The ink bottle should. Ink left over in the ruling pen can be saved by holding pen in a horizontal position with the point over the open bottle and tapping the edges of the nibs against the bottle.

A convenient pen-filling ink stand, which requires the use of only one hand, is shown at b. For removing dried waterproof drawing ink from pens or instruments, pen cleanto. Use of the Ruling Pen. The ruling pen, Fig. The proper method of filling the pen is shown in Fig. The hands may be steadied by touching the little fingers together. Twisting, instead of pulling, the stopper from a new bottle of ink, or one that has not been used for some time, will often save the stopper from being broken.

Horizontal lines and vertical lines are drawn in the same manner as for the corresponding pencil lines, Figs. Practically all the difficulties encountered in the use of the ruling pen may be attributed to 1 incorrect position of the pen, 2 lack of allowance for the quickdrying properties of drawing ink, and 3 improper control of thickness of lines and incorrect junctures. Position of the Pen. The pen should lean at an angle of about 60 with the paper in the direction in which the line is being drawn, and in a vertical plane con-.

The thumbscrew is faced away from the straight edge, and is adjusted, Fig. The correct position of the pen and the resulting correct line are shown in Fig. The same result may occur if, in filling the pen, ink is deposited on the outside of the nib that close the nibs. If the pen is held as shown at d , the outside nib pen may not touch the paper and the line is apt to be ragged. The triangle should be carefully drawn away from the line before being picked up.

One of the most compen will not “feed. If the pen will not make a fine line, the nibs have been screwed too close together, the ink has Inking. The pen should never be filled until the draftsman is ready to use it, because the ink dries quickly when not flowing from the pen.

Ink should never be allowed to dry in any instrument. Never lay a ruling pen down with ink in it. Some drawing inks have an acid content that will “pit” a ruling pen if left to dry in the pen repeatedly. The student should clean the pen frequently by slipping a stiff blotter or a folded cloth between the nibs. Sandpaper should never be used to remove dry ink. Dry ink should be removed by scraping very lightly with a pen knife.

Ruling pens constructed so that the nibs will separate for cleaning are available in a number of good designs, Fig. The stopper should always be kept in the bottle when it is not in use, since ex-. The various widths of lines used for inked Control Thickness of Lines. The draftsman must first develop a trained eye to distinguish fine variations, and must also acquire skill in producing the desired.

The student must remember that the thumbscrew alone does not control the width of the line. Factors affecting the width of a line with a given setting of the thumbscrew are:. Excess ink in the pen. Rapid movement of the pen. Sharp nibs.

Fresh ink and clean pen. Pen approaching the perpendicular. Before making a new ink line on a drawing, the thickness of line should be tested by drawing a test line on a separate piece of paper under the same conditions. Never test the pen freehand, or on a different kind of paper.

Always use a straightedge, and use identical paper. If excess ink. The pen should be held more nearly perpendicular when used with an irregular curve than when used with the T-square or a triangle. It should be in a vertical plane containing a tangent to the curve at the position of the pen. To make a tracing in ink, tracing paper, 71, or tracing fastened over the drawing, and the copy is made by tracing the lines.

When a drawing is important enough to warrant the use of ink, it is generally made on tracing cloth. Although the glazed side of the cloth formerly was intended as the It is common practice to make the pencil drawing directly upon the tracing cloth and then trace it with ink, thus eliminating the traditional pencil drawing on detail paper. Before the ink is applied, the cloth should be dusted with a small quantity of pounce, which should be rubbed in lightly with a soft fabric and then thoroughly removed with a clean cloth.

Instead of the special drafting pounce, any slightly abrasive powder, such as talcum or chalk dust calcium carbonate , applied with an ordinary blackboard eraser, may be used.

A greater difference in the widths of lines is necessary on tracings than on pencil drawings, because the contrast between blue and white on blueprints is not so great as that between black and white on drawings. Visible lines should be very bold. Extension lines, dimension lines, section lines, and center lines should be very fine, but strong enough to insure positive printing. The draftsman’s line gage, Fig. Mann, is convenient when referring to lines of various widths. In inking or tracing a pencil line, the ink line should be centered over the pencil line, as shown in Fig.

If this is done correctly in the case of tangent arcs, the line thicknesses will overlap at the points of tangency, as at c , resulting in smooth tangencies. Incorrect practice is shown in exaggerated form at d. Tangent points should be constructed in pencil, , to assist in. Pencil guide lines for lettering should be ruled directly upon the tracing paper or cloth, since guide lines on the drawing underneath cannot be seen distinctly enough to furnish an accurate guide for letter-heights.

For conventional ink lines, see Fig. Ink visible circles and arcs. Ink hidden circles and arcs. Ink irregular curves, if any. The correct point is. The nibs at c are too pointed, and as a result the ink tends to hang suspended in the pen and not touch the paper. Such a condition first manifests itself to the student in. The material in good ruling pens does not wear.

To sharpen the nibs, they should be opened and each nib sharpened on the outside, as shown in Fig. Great care must be exercised to prevent oversharpening one nib and thus shortening it. The bright points, indicating dullness, should be carefully watched and the nibs should be sharpened until the bright points disappear. Finally, to make sure that one nib has not been shortened, a few very light strokes should again be taken, as in Fig.

No attempt should ever be made to sharpen the inside of the nibs, for this always results in a slight convexity, which will ruin the pen. Ink Erasing. Mistakes are certain to occur in inking, and correct methods of erasing should be considered a part of the technique. If this occurs, it may be impossible to ink over the erased area. Best results are obtained if a smooth hard surface, such as a triangle, is placed.

An application of pounce or chalk dust will improve the surface and prevent running of the ink. When an ink blot is made, the excess ink should be taken up with a blotter, or smeared with the finger if a blotter is not available, and not allowed to soak into the paper. When the spot is thoroughly dry, the remaining ink can be erased easily. For cleaning untidy drawings or for removing the original pencil lines from an inked drawing, a sponge rubber, kneaded rubber, or artgum is useful.

The artgum is recommended for general use. Pencil lines or dirt can be removed from tracing cloth by rubbing lightly with a cloth moistened with carbon tetrachloride Carbona or benzine Energine. If the damage is not too great, an application of the powder will be sufficient. When a gap in a thick ink line is made by erasing, the gap should be filled in with a series of fine lines that are allowed to run together.

A single heavy line is likely to “run” and cause a blot. In commercial drafting rooms, the electric erasing machine, Fig. The one at b consists of a spline, to which ducks weights are attached.

The spline can be bent to form any desired curve, limited only by the elasticity of the material see An ordinary piece of solder wire can be used very successfully by bending the wire to the desired curve. Using the Irregular Curve. The irregular curve is a device for the mechandrawing of curved lines and should not be applied directly to the points, or used for purposes.

It is very important that the irregular curve match the curve to be drawn for some distance at each end beyond the segment to curve,. In placing the irregular curve, the short-radius end of the curve should be turned toward the short-radius part of the curve to be drawn; that is, the portion of the irregular curve used should have the. When plotting points to establish the path of a curve, it is desirable to plot more points, and closer together, where sharp turns in the curve occur.

Free curves may also be drawn with the compass, as shown in Fig. For symmetrical curves, such as an ellipse, Fig.

For example, at a the irregular curve is matched to the curve and the line drawn from 1 to 2. Light pencil dashes are then drawn directly on the irregular curve at these points the curve will take pencil marks well if it is lightly “frosted” by rubbing with a hard pencil eraser.

At b the irregular curve is turned over and matched so that the line may be drawn from 2 to 1. In similar manner, the same segment is used again at c and d. The ellipse is completed by filling in the gaps at the ends by using the irregular curve or, if desired, the compass. A great variety of templates is available for specialized needs.

A template may be found for drawing almost any ordinary drafting symbols or repetitive features. Ellipse templates, , are perhaps more widely used than any other type. Circle templates are useful in drawing small circles quickly, and in drawing fillets and rounds, and are used extensively in tool and die drawings. The links, or bands, are arranged so that the controlling head is always in any desired fixed position regardless of where it is placed on the board; thus the horizontal straightedge will remain horizontal if so set.

The controlling head is graduated in degrees including a vernier in certain machines , which allows the straightedges, or scales, to be set and locked. There are automatic stops at the most frequently used angles, such as and The chief advantage of the drafting machine is that it speeds up drafting. Since its parts are made of metal, their accurate relationships are not subject to change, whereas T-squares, triangles, and working edges of drawing boards must be checked and corrected frequently.

Drafting machines for left-handers are available from the manufacturers. For large drawings, the long T-square be Parallel-Ruling Straightedge. In such case the parallel-ruling straightedge, Fig. The ends of the straightedge are controlled by a system of cords and pulleys which permit the straightedge to be moved up or down on the board while maintaining a horizontal position.

Drawing Papers. Drawing paper, or detail paper, is used whenever a drawing made in pencil but not for reproduction. For working drawings and for gen-. Most industrial drafting rooms use standard sheets with printed borders and title strips, and since the cost for printing adds so little to the price per sheet, many schools have also adopted printed sheets. The best drawing papers have upwards of per cent pure rag stock, have stronger fibres that afford superior erasing qualities, folding strength, and toughness, and will not discolor or grow brittle with age.

The paper should have a fine grain or “tooth” which will pick up the graphite and produce clean, dense black lines. However, if the paper is too rough it will wear down the pencil excessively, and produce ragged, grainy lines. The paper should have a hard surface so that it not “groove” too easily when pressure is applied to the pencil.

The Board and Strathmore, come in several thicknesses, as. Tracing paper is a thin transparent paper upon which Tracing Papers. Tracings are usually made in pencil, but may be made in ink. Most tracing papers will “take” pencil or ink, but some are especially suited to one or to the other.

Tracing papers are of two kinds: 1 those treated with oils, waxes, or similar substances to render them more transparent, called vellums; 2 those not so treated, but which may be quite transparent, owing to the high quality of the raw materials and the methods of manufacture.

Some treated papers deteriorate rapidly with age, becoming brittle in many cases within a few months, but some excellent vellums are available. Untreated papers made entirely of good rag stock will last indefinitely and will remain tough. For a discussion of tracing methods, see 61 and Tracing cloth is a thin transparent muslin fabric, cotton, Tracing Cloth.

It is much more expensive than tracing paper. Tracing cloth is available in rolls of standard widths, as 30″, 36″, and 42″, and also in sheets of standard sizes, with or without printed borders and title forms. For pencil tracings, special pencil tracing cloths are available. Many concerns make their drawings in pencil directly on this cloth, dispensing entirely with the preliminary pencil drawing on detail paper, thus saving a great deal of time.

These cloths generally have a surface that will produce dense black lines when hard pencils are used. Hence, these drawings do not easily smudge and will stand up well with. The use of the basic sheet size 8V’XH”, and multiples thereof, permits filing of small tracings and of folded prints in standard files with or without correspondence.

These sizes can be cut without waste from the standard 36″ rolls of paper or cloth. The alternate system based on size 9″X12″ is widely used in the automotive industry and has the advantage of slightly larger areas.

For American Standard sheet layouts, see Fig. Note that in both systems for sheets size C and larger, zoning letters may be used. The sizes of the zone spacings. All of the following constructions are to Mechanical Drawing Problems. The steps in drawing this layout are shown in Fig. Draw all construction lines lightly, using a hard pencil 4H to 6H , and all required lines dense black with a softer pencil that is, lightly F to H.

If construction lines are drawn properly they need not. The drawings in Figs. If ink tracings are required, the originals may be drawn on detail paper and then traced on vellum or tracing cloth. For any assigned problem, the instructor may require that all dimensions and notes be lettered in order to afford further ;. Using Layout A-2, divide working space into six equal and draw visible lines, as shown.

Omit dimensions and instructional notes. Using Layout A-2, divide working space into six equal and draw lines shown. In first two spaces, draw conventional lines to match those in Fig. In remaining spaces, locate centers C by diagonals, and then work constructions out from them. Omit dimensions and instructional Fig. Using Layout A-2, draw figures in pencil, as shown. Use bow pencil for all arcs and circles within its radius-range. Using Layout A-2 and arrangement of Fig.

Omit all dimensions and instructional notes. Modern European alphabets had their origin in Origin of Letter Forms. Egyptian hieroglyphics, which were developed into a cursive hieroglyphic or hieratic writing. This was adopted by the Phoenicians and was developed by them into an alphabet of twenty-two letters. This Phoenician alphabet was later adopted by the Greeks, but it evolved into two distinct types in different sections of Greece: an Eastern Greek type, used also in Asia Minor, and a Western Greek type, used in the Greek colonies in and near Italy.

In this manner the Western Greek alphabet became the Latin alphabet about b. The Latin alphabet came into general use throughout the Old World. Originally the Roman capital alphabet consisted of twenty-two characters, and these have remained practically unchanged to this day. They may still be seen on Trajan’s Column and other Roman monuments. The letter V was used for both U and V until the tenth century.

The last of the twenty-six characters, J, was adopted at the end of the fourteenth century as a modification of the letter I. The dot over the lower-case j still indicates its kinship to the i in Old English the two letters are very similar.

The numerous modern styles of letters were derived from the original ;. These letters were introduced into England, where they became known as Old English. The early German printers adopted these letters, and they are still in use in Germany. The early Italian printers used Roman letters, which were later introduced into England, where they gradually replaced the block letters ‘Lettering, not “printing,” is the correct term for of printed material on a printing press.

Gothic Italics orTixtltahc. German text. The term refers If the letters are. Roman letters include Old Roman and Modern Roman, and may to. Inclined letters are also referred to as Italic, regardless of the shown in Fig.

 
 

 

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