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heavy at the bottom, and medium at the top, while No. 5, a horizontal hollow cylinder is shaded in an opposite manner, as will readily be seen. Additional effect is gained by using the heavy shade lines as described in the preceding article.

In drawing these shade lines, the efect of shade is gained entirely by the closeness of the lines together, the heavy shading being produced by drawing the lines closely together and the light shading by giving considerable space between the lines, additional effect being given by breaking the lines as appears on most of the figures. The skill in doing this work comes from the ability to vary the spaces between the lines in such a manner that the figure will appear cylindrical at all points, and nowhere flat, as it would if the spacing was not varied continually.

The greater the diameter of the cylindrical figure, the greater should be the space between lines at the lightest point. The proper spacing of these lines is gained only from practice, it being a thing that cannot be reached from any exact instructions, or from measurement.

To those who are not interested in the inking of drawings, we would say that this shading can be done also with lead pencil. In Fig. 63, No. 1 shows an elbow shaded. The curved lines are all struck from the one center, and should be put in first, and the straight lines connected with them afterward. In shading branches, as Nos. 2 ard 3, the lines of intersection should be drawn in first, and

the shade lines of the branch should end at those lines.

Fig. 64 shows the principle of line shading applied to a system of piping.

As we have already intimated, this work is more ornamental than otherwise, and a knowledge of its use will often be found handy. As our regular practice exercise, we give this time, Fig. 65, an elevation of the hot and cold water supply system for a two-flat house, and have shown the lines of pipe as single lines, the cold pipes being represented by solid lines, and the hot by dotted lines. This method is often preferable to using two parallel lines to show the pipe, as it is simpler to draw, takes less time, and often shows off the work fully as clearly. It will be understood that our illustrations being designed for reproduction as cuts in a paper, have to be drawn in black ink. Under ordinary conditions, different colored inks could be used to advantage, however. For instance, instead of dotting the hot water pipes, as we have to in this case to make our distinction from the cold water, the hot water pipe might be put in with solid red lines, with good effect. If desirable, a back air system might be put in with one color, while a different color was used on the drainage part of the work.

Sometimes, also. it is required to make a drawing in which part of the work is old work, and the rest new work. In this case, one color to show the old and another to show the new, makes good work, and is more readily distinguished.

W

E have said nothing so far concerning sectional drawings, but as they constitute a valuable aid in the clear representation of many kinds of work, it will be worth our while to devote some space to their consideration. From a comparison of Nos. 1 and 2 in Fig. 66, we shall be able to see wherein the value of sectional drawings lies.

No. 1 represents a Fuller bibb, and the dotted lines represent the inside working parts.

No. 2 represents the same thing, but instead of drawing a plain view as in No. 1, the bibb is considered to be cut through along the center line, and the front half set aside. This allows a full view of the other half. A sectional view of the bibb is a view of this half section such as No. 2 gives, and it will be seen at once that the sectional view is far clearer than that shown by No. 1. To show that it is a sectional drawing, the part that is cut through is always sectioned or crosshatched. By this is meant the parallel lizes drawn close together, which designate the body of the bibb. These lines nay be drawn with either the 45 deg. or 30 deg. triangle. Every point of any given piece should be sectioned in the same way. For instance, the inlet end of the bibb, which screws onto the body, is represented in the drawing by a section of metal above the center, and one below, both of which, being a part of the same piece, should be sectioned by lines drawn in the same direction and at the same angle. It is often the case that these sections are represented by different colors instead of section lines, the different colors representing different pieces of the article in question.

When section lines are used, and the different sectioned parts are in contact

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tioning them in the manner that the rest of the bibb is seen.

No. 1 of Fig. 67 represents a sectional view of a certain type of water closet. In this case the whole section is of one piece only, and in such a case, a solid black section looks well. This could not be sectioned in this manner if there were several parts to be sectioned for in using a solid color, there would be no way of making a distinction between the several parts. In plumbing drawings it is often required to represent water, and we know of no better way than that shown in connection with the water closet, that is by horizontal light lines, made up of alternate dots and dashes. It will be observed that in a sectional view of the water closet, the flushing rim would be cut through at either end, but the main part of the rim, curving backward as it does, away from the line of sectioning, would be drawn in full, in the manner in which we show it. No. 2 represents a

line of soil pipe underground. A full black section looks well on such work, better in fact than the section lines, which are really used mostly on larger surfaces. To distinguish the lead joints from the pipe, they are made with small dots. The concrete floor may be made as we have indicated, and the ground surrounding the pipe in an indefinite manner, by having short lines made with the drawing pen, and interspersed with lines made with a common pen.

In Fig. 68 we have represented part of the base of a water closet, connected by brass flange of a certain style, with the lead bend; the fixture being vented from the bend. This we give to show the section of several different materials brought together on the same drawing.

It is a common thing with draughtsmen, to use certain different styles of section for different metals, especially in the drawings of machines, but for our use this is unnecessary, the main point being the use of such styles of sectioning as will clearly distinguish the different parts of the same drawing, one from the other. Thus in Fig. 68 the crockery is shown in section by dot and dash lines, the rubber gaskit by a fine dotted surface, the brass flange by 45 deg. section lines, the solder sections by 45 deg. lines drawn in the opposite directions, the lead by solid black surface, and the wood by lines representing the grain of wood. will be noticed that the back air pipe is in sections only a short distance up, after

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FIG. 68.

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the sectioned and unsectioned parts is made by an irregular section, as shown.

Another point which will be of value to the plumber in making drawings of dif ferent fixtures, fittings, etc., is the making of threads. This we show in Fig. 69. No. 1 represents a right-hand V thread. The tool that is used in cutting this kind of thread is sharpened or ground on its cutting point at an angle of 60 deg. Consequently, in drawing the threads they are made at this same angle. If it is desired to do this work with exactness, the number of threads to the inch is first found, eight being the number used in our illustration.

The upper line is then laid off into one-eighth inch spaces and the lower line also, the latter, however, being spaced one-half space or one-sixteenth in this case, in advance of the upper spaces. This is to give a pitch to the thread, for otherwise the thread would be straight up and down.

Having laid out the spaces, put in the Vs, using for this purpose the 30 deg. triangle.

All the lines sloping in one direction and first put in, and then the triangle is reversed and the lines pointing the opposite way drawn in.

The outside and inside points are then connected by straight lines. No. 2 shows a left-hand thread. The layout for both is the same, the distinction between right and left hand threads being gained by properly connecting the long cross lines.

Nos. 3 and 4 show the two kinds of thread drawn in a vertical position, and No. 5 shows a method often used for indicating a thread, where it is not desired to use so much time as is necessary in laying out a regular thread.

No. 6 shows a sectional view of a threaded piece, and No. 7 a sectional view of a hollow piece threaded on the outside. Naturally, in a sectional view, the lines connecting the top and bottom of the threads are not seen, the V only being shown.

Owing to lack of space, we omit the regular exercise for this article, and would advise in its place, practice on sections and threads.

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