rollers, and similar jobs; and though sufficiently simple for straight pieces, it becomes very complicated when ap plied to a bend. It is not, therefore, usual to stave up a bend, but to build it in the manner illustrated in Fig. 143.

Fig. 143.

G

The operation is, to first draw the bend in plan, of the full size, upon a board. Let B, in Fig. 143, represent the center from which it is struck, the plan in this case being a quarter circle bend, denoted in Fig. 143 by the line C D F, the line G, and the sections of a circle, H and J. We have decided to build up our pattern with five pieces, an end view of the half pattern being denoted by the circle CE F, and five pieces or layers being denoted by dotted lines, so that by adopting this method we show the plan and end view of the bend in one drawing. It would be well now to cut out forms, in card or in very thin wood,

as templates, one for each of the pieces, marked from 1 to 5 respectively. To obtain these templates, we draw the line C B; and from the center, D, we describe the semicircle C E F, representing the diameter of the half bend. We then lay off the tires from 1 to 3, as shown by the dotted lines; and to find the bends necessary for each respective piece, we proceed as follows: Setting our compasses at a distance equal to that between the center from which our bend is struck (B in Fig. 143) and the extreme outside of the piece marked 1, we draw the quarter circle denoted by the dotted line, K. Then setting our compasses from D to the inside of piece 1, we draw from the center, D, the quarter circle denoted by the dotted line, L. The space included between those quarter circles, and denoted by IT, is the sweep for the piece 1; and we may cut it out for use as a template wherefrom to mark out piece 1. By setting the compasses in like manner for each respective piece, 2, 3, 4, and 5, we obtain the templates, 2 T to 5 T, respectively, for use in marking out the pieces upon the board from which they are to be sawn. In building the pieces up, we lay those forming the lower tier on the plan previously drawn out on the piece of board, putting them a little outside the lines, to allow for finishing. We then temporarily fix them in that position-the faces being, of course, planed up. We now glue on the next fier. It is well, however, to have a semicircle made of a piece of thin wood, and of the size of that shown in Fig. 143, by C E F, which we may place upright against the ends of the first tier, as a guide in adjusting the position of the second and succeeding tiers. The number of tires is discretionary; but it is well to have the top piece comparatively thick, so that it shall not be liable to curl, as it would be apt to do, if the turning left it thin. If the joints of the tiers are' well surfaced and well glued, neither nails nor screws will be needed. It is not compulsory to make each layer a

continuous piece, and it will save stuff to make every alternate layer of two pieces; but the bottom and the top layers are better, if each be made in one piece.

It will be observed that this staving up a bend is both laborious and wasteful; yet there are cases in which it becomes imperatively necessary to make it in this manner. A very common job of this kind is lagging up a steam pipe, such as shown in Fig. 144. The pipe is usually covered with felt or some other non-conducting material, and

Fig. 144

covered round with mahogany or walnut. Now, it would be very unsightly to have the joints in the bend out of line with those on the straight part of the pipes. A hollow bend of wood has, therefore, to be constructed, having in it the same number of staves as there are for the straight pipe. To get out the pieces for such a bend, we proceed as illustrated in Fig. 145, in which there are shown 6 sections or staves, the semicircle G H representing the required inside diameter of the bend; while the semicircle A E represents the required outer diameter. We then divide off one of the semicircles into the required number of divisions; and we draw radii, and then form rectangles around each division or space representing a stave, as shown by dotted lines in Fig. 145 at 2, 3, and 5. The method pursued in getting out these staves is precisely similar to that pursued in building up in our

last example. In this case, however, as each stave is fitted to its fellow, it should be held to its place by dowels-that is, small pins of wire placed at frequent intervals-which will serve instead of glue, which would not answer, by reason of the heat from the steam pipe. The disks upon which the bend is built, and of which there should be at least three, are merely temporary; and therefore the staves are not to be fastened to them,

Fig.145.

except for convenience, so as to keep them in position. For this purpose, a piece of paper, with a little hot glue on each side, should be placed between the stave and the disk; it will make a fastening sufficiently strong, if a little pressure be applied during the drying. Neither nails, screws, nor staples, are admissible on this kind of job, as they would mar the appearance of the work when finished and polished. The two halves of the bend being completed, they are made to go together with loose pegs-that is to say, pegs that do not fit the holes tightly, as the dowels do. The halves should be held together by polished brass or plated bands; and the neatness of the finished appearance will amply repay the cost and the trouble, for the polished wood forms a pleasing contrast to the contents of an engine room, where almost everything the eye can rest on is iron,

CHAPTER IX.

EXAMPLES IN GLOBE VALVES.

In Fig. 146, we have for an example a common globe valve, shown partly in section and with a gas thread cut

Fig.147

in the openings. The flanges vary in shape; but, as a rule, small valves are provided with hexagons, and large ones with round flanges suitable for bolting to similar flanges to make joints. For small valves, say up to 2 inches, the pattern is usually made with the hexagons cut out of the solid, but for sizes above that, they should be made in separate pieces, as shown in Fig. 147, and screwed to the pattern, so that in case of necessity they may be removed, and flanges substituted in their stead. In Fig. 148 we have a perspective view of the finished pattern; and Fig. 149 represents the pattern as prepared, ready to receive a flange or hexagon as may be required. A globe valve pattern should be made in