Читать книгу Carpentry and Woodwork - Edwin W. Foster - Страница 19

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Among the many useful articles which can be made with the knife in thin wood, with carving as enrichment, are the numerous desk accessories, such as envelope holders, letter racks, stamp and pen boxes, pen trays, blotting pads, etc. The boys, after exhausting the subject of pencil boxes for school use, took up the design and construction of letter racks. These, they decided, should be in two compartments for answered and unanswered letters. This called for three uprights, or partitions, and a base. They decided to make them of about uniform dimensions, as shown in the blank form (Fig. 67). The problem of the outline was somewhat affected by the fact that the front was to be carved. This called for a simpler outline than would have been the case had they expected to leave the surface plain. Some of the designs they worked out are shown in Fig. 68.

The form marked a was selected as a beginning, the three partitions cut out exactly alike, and the front piece carved as shown in Fig. 69. The middle partition and back piece were left with plain surfaces.

Fig. 67. Parts of letter rack

The cutting of the grooves in the base was a new problem, and Harry was allowed to try his skill with a chisel. The method used was first to make the drawing shown at a, Fig. 67. The long side lines of each groove were scored with the point of the knife, going over each line several times, to make the cut as deep as possible. An under cut was then made, as shown in the figure.

Fig. 68. Boys' designs for letter racks

The wood in the centre was removed with a ¹⁄₄-inch chisel, and the process continued until a uniform depth of ¹⁄₄ inch was reached. After all three grooves had been cut, the edges of the base were bevelled with the plane. This bevelling could have been done readily with the knife, but much time was saved by using the plane, always doing the long sides first.

In all the letter racks shown in the illustrations the construction was the same. First, the three blank partitions were made, then finished in their outlines with knife and sand-paper. The carving was always drawn carefully on the surface of the front piece. Third, came the making of the base, and last, the gluing of the partitions into the grooves. To increase the strength of a letter rack, ³⁄₄-inch brads can be driven from the bottom into the partitions, but where this is done it is safer to draw pencil lines on the bottom directly under the centre of each partition. Place the point of the brad exactly on the line before hammering.

Fig. 69. Form "A"

Although the forms of the letter rack are endless, the one which our boys found most interesting was based on the ellipse. It called forth a very instructive drawing lesson. Ralph showed Harry first how the figure could be drawn by a string, with two pins to represent the foci of the ellipse. The figure has two dimensions called the major axis and minor axis. (Fig. 70).

Fig. 70.

The combined length of the two lines drawn from any point on the ellipse to the two foci must always be the same and equal to the length of the major axis. This is readily seen with the two pins and string. (Fig. 71.)

Fig. 71. Drawing the ellipse with string and pins

The pencil point as it traverses the ellipse represents any point, and the string remains the same length. Where it is required to draw an ellipse of definite size, say two by three, it becomes necessary to find the foci before the string can be used, and as it requires considerable skill to get the string the exact length, Ralph showed the boy another way, called the trammel method. (Fig. 72.)

Suppose the problem is to construct an ellipse 6 inches × 2¹⁄₂ inches. First draw the two lines a b and c d at right angles, intersecting at the exact centre. Take a straight piece of paper, lay it along a b with one end at a. Make a dot on the edge of the paper where the lines cross, and mark it x. Next, lay the same strip of paper along c d, with the original end at c, and again mark a point where the lines cross. Mark this point y. At any position of this strip of paper when the points x and y touch the two axes a b and c d, the end of the paper strip will be on the ellipse. By shifting this paper trammel and keeping the two points on the axes a series of points may be made at the end of the paper. Connecting this by a pencil line will complete the ellipse. This is a very simple method and a very accurate one.

Fig. 72. The trammel method

Fig. 73. The ellipse used in carving designs

Our boys drew this figure, 6 × 2¹⁄₂ inches, with a trammel and then worked out the design from it shown in Fig. 73. It made a very satisfactory form for the letter rack, and gave an elliptical space for carving, a new problem in chip carving design.

Fig. 74.

Two more of these elliptical designs are shown in Fig. 74.

Another feature of this rack was a change in the middle partition; the form is shown at Fig. 75. The making of the base and gluing into the grooves were similar to the earlier designs.

The next design was characterized by an outline composed largely of straight lines.

The middle partition was lower than the front and back pieces, as shown in Fig. 75.

Fig. 75. A neat design for a letter rack

The boys found a great deal of pleasure in working out a decorative scheme for the carving. Having discovered how easy it is to carve the long flowing curves, they introduced them wherever possible. The general shape of the carved section must of course conform to the outline of the wood, but while filling in these flowing curves they soon learned to sketch them in free-hand.

Fig. 76. A letter rack decorated with the veining tool

To a person who has not tried this work or who has not begun with simple cuts it appears very difficult, but when it is remembered that only one cut can be made at a time and that each chip is a triangle, even if its sides are slightly curved, it actually proves very easy, and within the power of any normal boy to accomplish.

Fig. 77. The pen-holder

Harry was introduced at this time to the use of the veining tool, a fine gouge with a cross section almost V-shaped. This was used to emphasize the outlines of the designs by simply pushing ahead directly on the lines. When veining straight lines, it may be guided by a ruler or other straight edge, but for curves, a free-hand movement is necessary. A very good practice piece is the design shown at Fig. 76. This may be applied to the front of the letter rack design. (Fig. 69.)

The pen-holder shown at Fig. 77 is one of a large number which were made by the boys. The pieces were cut out with a knife to the blank forms shown. On all pieces like these, afterward to be assembled, the edges were made straight and square on the shooting board, and the carving done before assembling. This pen-holder was put together with ³⁄₄-inch brads with the exception of the front, which was glued, as it was thought best not to have nails showing on this important side. (Fig. 78.)

Fig. 78. Pieces composing pen-holder

Photograph by Arthur G. Eldredge

Using the Veining Tool.