



Form Work; Modeling 58. Making a Cylinder.—The cylinder is evolved from the square prism by increasing the number of sides until a prism is formed with so many sides that its surface can be easily transformed into a cylinder by means of sandpaper. (1) Begin by making a square prism which shall have the same dimensions for its width and thickness as is desired for the diameter of the cylinder. (2) Change this square prism to a regular octagonal or eightsided prism by planing off the four arrises. The gage lines which indicate the amount to be taken off of each arris are made by holding the gage block against each of the surfaces and gaging from each arris each way, two lines on each surface. These lines must be made lightly. The distance at which to set the spur of the gage from the head is equal to onehalf the diagonal of the square end of the prism. Fig. 109. Since the ends are less likely to be accurate than any other part, it is advisable to get this distance as follows: Lay off two lines on the working face a distance apart equal to the width of the prism. These lines with the two arrises form a square the diagonal of which can be measured and onehalf of it computed. Carpenters in working on large timbers lay the steelsquare diagonally across so that there are twentyfour divisions from arris to arris. They then mark off the timber at seven and seventeen inches. Fig. 110. These numbers,while not mathematically correct, are near enough for practical purposes. In planing the arrises off, the piece may be held in the vise or placed against the benchstop. Fig. 111. Care must be taken not to plane over the lines, for not only is the one side enlarged, but the adjacent side is lessened, thus exaggerating the error! (3) Judging with the eye the amount to take off, plane the eight arrises until there are sixteen equal sides. Again plane the arrises, making the piece thirtytwo sided. On a small piece this Fig. 111 will be sufficient j if the piece is large; the process may be continued until the piece is practically a cylinder. (4) To finish a small cylinder wrap a piece of sandpaper aiound it, rub lengthwise until the surface of the wood is smooth and the piece feels like a cylinder when revolved in the hand. 59. The Spokeshave.—Fig. 112. The spokeshave is used principally to smooth curved surfaces. It may be drawn toward or pushed away from the worker, whichever is more convenient. By means of screws the blade may be adjusted to take light or heavy shavings. The spokeshave is practically a short plane with handles at the sides, and in using it the aim should be, as with the plane, to secure silky shavings of as great length as the nature of the work will allow. 60. Making Curved Edges.—To make curved edges on a board, fingergage on each side, lines which shall indicate the amount of curvature. If the curve is to be a gradual one reaching from one of these lines over the middle of the edge to the other, two lines should also be fingergaged on the edge. Fingergage from each side using a distance equal to onefourth the whole thickness of the piece. This process may be repeated until the surface of the edge is practically a curved surface. With a piece of sandpaper held as shown in Fig. 115, rub until the surface is smooth and evenly curved. 61. Modeling.—This term is used to apply to the method of making objects of such irregular form that the judgment of the worker must be depended upon to give the correct result without the aid of gage and knife marks. The forming of a canoe paddle or a hammer handle is a good illustration. Generally a little forethought will show a way in which the piece of work may be partly laid out with knife, square and rule. To illustrate, take the hammer handle, Fig. 116. The steps would be as follows: First, plane a face side and a face edge, and square the two ends so that the piece shall have the length desired for the finished handle. Second, draw a center line on the face side, parallel to the face edge and lay off on either side of this the two straight lines which shall indicate the amount of taper; also sketch in the lines of curvature. Plane the two edges to the tapering lines and square with the face side. Then cut to the curved lines, keeping this surface also square with the face side. In a similar manner, lay off on the face edge a center line parallel to the face side, mark the taper and lines of curvature, and work these surfaces as in the second step. Third, the piece may be laid off still further by drawing on the larger end the form of the ellipse which that end is to assume. With spokeshave, judging the curves of the middle with the eye, work out the desired form. The steel scraper is to be used for finishing after the piece has been made as smooth as is possible with the spokeshave.
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