at top lett-Iiand corner, and work across the sheet horizontally, then work downwards. This avoids continually going over the finished work with the squares. In copying from examples such as are given in this book, or in designing original work, plans should be drawn tirst, then sections, and finally the elevations projected from the two former.
I)o not rill in all the details or hatch sections as you go in any one part of a set of drawings, but get in the chief members, etc., first, in each of them ; this will localise many of the interior lines and prevent overrunning, also, in case of alterations, will save much time.
In making drawing's at examinations where speed is essential, position on the sheet is not of much moment, but the solution should be commenced by putting in the skeleton or outline of the problem as indicated in the question, and tilling in such details as suggest themselves, and as time permits. Always avoid repeating exactly similar parts and confine your attention to important constructive features, rather than minute details. For example, if asked to draw a partition, do not spend two-thirds of the time carefully spacing and drawing in a series of studs, all of which are exactly alike, but draw in all the main timbers first, or even half of them if the two sides are alike, finally putting in a few studs to inform the examiner that you know they should be there. Again, if you are drawing a ledge door it is more important to show the proper position of the braces than it is to indicate nail-heads in the ledges. The examiner will assume you know that the door is to he nailed together if you show him that you know how the members are arranged.
In Laying Off Dimensions it is better to use scales than dividers, but if the latter art: used do not prick holes 1:1 the paper with them —this spoils the; appearance of any drawing—but lay the dividers sideways to the line, and tick otf their points with the pencil. Do not lay off dimensions from one another successively, but measure from a common point either at the end or middle of the line or
member. In tlie lirst method an error at one point is repeated throughout, whilst in the second it is confined to the original point and is readily located.
Measuring Curved Lines.-—It is often necessary to do this with accuracy when a stretch-out or development of the surface is required. T he best method ^ is to set the spring bow dividers with ^J a small opening, varying with the . quickness of the curve, and stepping
^Lengta'ofa C urved*! ine lt *lonS the curved line, counting how many steps are required to reach from end to end, then transferring to a straight line a like number of steps. It is not necessary to divide the curve exactly into equal parts. If the last step overpasses the end, mark where it reaches and lay off the same number of steps on the straight, then come back and set the dividers exactly to the space exceeded, and mark this within the last mark or step (see Fig. above, where the straight line contains the sixteen divisions of the curved line).
The Stretch Cut of a semicircle may be approximately obtained by drawing lines through the ends of the diameter at an angle of 60 ° with the same, as shown. The set square may be utilised as indicated by dotted lines, then drawing a line tangent to the curve and parallel to the diameter as A-B which will be very nearly the length of the curved line.
with the compasses, hold tlie Circle instrument lightly between linger and thumb as near the top as possible, to avoid closing the legs and revolve steadily, to avoid piercing the paper. If a number of concentric circles have to be described make a cross on a thin piece of card and mark similar crossed lines on the drawing. Make the two sets of lines coincide.
This will locate the centre, and the compasses may be used on the card without damaging the drawing.
A piece of celluloid is sometimes used instead of the card, as the centre can be seen through it. Describe the smallest circles first, as revolving the compass at an angle when opened wide enlarges the hole.
Draughtsmen's Lines and Signs.- It is desirable for the benefit of those having to read drawings that a simple and uniform system of lines should be used in [
for example, a dotted line -------¿r—r- —^pf^
drawing where a full line A-------------------~A"
would be used in others. »- — t-f — -<*-t0 *----K-*---* 7
a quantity of work turned ^ and Signs ujed by DraugJltsmen out by leading draughtsmen I conclude that the following list most nearly represents prevailing practice.
The Fine Line (No. 1) is used for all interior and inferior ines in a drawing.
The Full or Heavy Line (No. 2) for outlines or boundaries. Note, the line should be of a regular thickness throughout, the extent of which will depend upon the scale of the drawing, and it should not be as shown in No. 3, uneven and irregular.
The Dotted Line (No. 4) for hidden parts, or parts out of the plane of section upon which the drawing is made.
The Chain or Break Line (No 5) is generally used to indicate a proposed new position in the object which is shown in full line, or vice versa ; it is also used in lieu of dotted lines where the latter might be confused with projectors.
Projectors are always dotted when left upon a drawing, which occurs seldom, except for teaching purposes. In
32 DRAUGHTSMEN'S LINES
ordinary work they are rubbed out after the inking in is completed.
The Dot and Dash Line (No. (>) is invariably used to indicate line of section, accompanied by a capital letter at each extremity for reference. It is also used with an abbreviated dash, for paths of a moving portion, such as a door.
Dimension Lines (No. 7) are, as their name indicates, intended to guide the eye along the route of a dimension. Thejr are a variety of the break line with longer intervals and shorter dashes, the object being to make them as unobtrusive as possible, subject to their ready indication of the extremities of the dimension located by arrow heads. Usually in architectural drawings they are made in blue ink and centre hues are made in red.
The Broken or Irregular Line (No. 8) isused to indicate that the drawing or part on which it occurs is much longer or wider than is shown, the real dimension being specified in figures. The object of so breaking a drawing is to curtail its space, and is a common practice in preparing " rods " or other full-size drawings in so far as widths are concerned. Upon rods, the length is never broken ; to do so would render the rod useless for setting-out from.
The False Line (No. 9) is, as shown, " false " ;n two senses, as both the line to be removed and the indicated line should rightly be in pencil, which, of course, is impossible in a printed example. When making a drawing of any importance a number of tentative lines may be necessary; again, the inexperienced draughtsman will place lines where he does not intend them. It is not always the best thing to erase these at once. Quite frequently they may be utilised, and constant use of the rubber (himages the paper, so, when a false line is made in pencil which is not intended to be inked-in, the draughtsman does not rub it out at once, but " scribbles " it out, as shown, only in pencil ; and all vanishes with the linal cleaning-olf.
Sometimes it is found necessary to dot a line which it was first intended to draw full. In this case do not rub it out, but " herring bone " it as shown in No. 10, of course again ill pencil only.
Sectioning- or Hatching.—The method of indicating various materials by special hatchings is again coming iuto use by the professional draughtsman, in consequence of the facility with which uncoloured line drawings may be reproduced by the various sun printing and other processes. When, however, only one or a few copies are required, the drawings are much clearer to read if the various materials are dist inguished by colouring the sections, but as it is of
Hatchings for Materials little service describing colours without reproducing tliem, these instructions are confined to black-ink sectioning. The chief conventional hatchings are shown and described above.
It must be understood that these various hatchings are to be applied to parts in " section " only. " Graining," to indicate wood in elevation, should be indulged in very sparingly; its copious use indicates the amateur draughtsman who thus hopes to hide his faults of design or construction. Technical drawings are not intended to be pictures, and they should indicate their meaning clearly, definitely and economically. A few deft touches with the pen to indicate direction of the grain or to distinguish wood from space is all that is permissible or desirable.
TECHNICAL DRAUGHTSMEN'S STANDARD LIST OI- MATERIAL HATCHINGS (see Page 33)
Brick — Medium ruled lines at an angle oi 45' with chief dimensions, not too closely drawn.
Stone.—Similar lines alternately with dotted or broken lines.
Wood.—Lines slightly curved drawn freehand, representing the annual rings. Large timbers are indicated by a few radiating " shakes." Adjacent pieces should be distinguished by drawing the lines in reverse directions.
Wrought Iron—Alternate thick and tLin lines ruled at an angle of 45°.
Cast Iron —Closely mled lines at angle oi 45'" with main dimension.
Steel —Broken fine lines at 45
Lead.—Reversed medium lines or " cross hatching."
Brass.—Dot and dash lines perpendicular to longest side.
Zinc.—Heavy black ruled lines at 45° to longest direction.
Glass--Longitudinal ruled line lines.
Glass m Elevation - Diagonal ruled lines, lightened or erased with the rubber irregularly to give elfect of broken light.
Concrete.—Irregular curved shapes and dashes.
Earth.—Interlaced cross hatching in patches.
Plaster.—Points of irk or splashes.
Small Sections in Metal when it is not desired to indicate any special kind, are put in solid black.
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