An equipment for mechanical drawing, except the instruments, can be easily made in the shop by any boy who has had some practice with tools.

The drawing board is the first thing needed, and several makes are in use, the object of all of them being to insure a true flat surface by overcoming the natural tendency of wood to warp.

Shrinkage will take place in spite of all precautions, but this is not a serious matter, and does not affect the usefulness of the board.

All boards, it is conceded, should be "built up," rather than consist of one piece. The idea is that the warping of one piece is somewhat counteracted by that of the adjoining pieces in other directions.

Fig. 206 shows three forms in common use. At a the ends are united to wide cleats by a tongue and groove joint.

In shrinking and expanding with weather changes, the board is free to slide along the joint, being glued only at the centre.

At b two dovetail-shaped strips are inserted on the under side across the grain. This is more difficult cult to make on account of the shape of the groove, but it is otherwise satisfactory. At c two strong cleats are fastened across the under side by screws. This is the easiest and least satisfactory method, as the cleats are often in the way, making the board clumsy, and furthermore it does not allow for shrinkage, unless the screws are secured in grooves instead of in plain holes.

A good proportion for a small board is 24 × 18 inches. If the first method of construction is decided on, glue up four or five strips of well seasoned white pine, ⁷/₈ inch thick, of the width desired, and four inches shorter than the final length of board. Place in clamps for twenty-four hours, and when dry dress down perfectly true to a thickness of ³/₄ inch. Test for warp and wind, and square the ends.

Square up two pieces of stock 2¹/₂ inches wide, with a length equal to width of board. For the tongue and groove joint, a set of tongue and grooving planes will be necessary. Two cutters for this purpose come with the modern universal plane, and if available this may be used. In either case, set the depth gauge at half an inch, and plow a groove on one edge of each strip ¹/₄ inch wide to the full depth, as shown at d. On both ends of the board, plane the tongue same size as groove at e. Coat the tongue at each end of board with glue for a distance of six or eight inches at the centre, fit the end strips in position, and place in clamps over night. When dry, give the surface a final truing up, and also the ends, as the clamps may have made a slight change.

Go all over the surface with a sand-paper block, using 00 sand-paper, and shellac the board all over. When dry rub flat with the sand-paper block. Make a final test for any possible inaccuracy, and the board is ready for use.T square and triangles may be made, but as rubber or celluloid triangles are better in some ways than wood, the former are recommended.

The T square is a very pretty little problem in woodwork, and may be made as follows:

The design for the head may be either a or b (Fig. 207), a being simply a rectangular piece of hard wood, with two rounded corners; b is laid out as shown, sawed near the line and curved side finished with spokeshave. The straight side should be perfectly straight, as any variation will give horizontal lines out of parallel.

The blade may be of one piece, or built up. A very satisfactory combination is to make the head of black walnut, and the blade of hard maple, with black walnut edges. It will pay to make a special shooting board for this work, and to make several T squares at the same time. This shooting board should be slightly longer than the blade. (See Fig. 206.)

Gauge a line at a distance x from the edge, equal to the width of 2 inches, and tack a straight strip of wood up to this line as a guide. When the blade has been planed to its thickness of ¹/₈ inch, it is to be placed in space x and planed to width.

To plane a piece of hard wood down to an eighth of an inch, tack it to a pine board with three 1-inch brads. The location of these brads can be such that only one hole will be left in the blade to be filled up afterward. One should be in the position of the central screw over the head, the second at the point where hole h is to be bored, the third at about the centre of the blade. Set these brads slightly below the surface, and dress down smooth.

When tested and found true, lift the blade by inserting a knife blade under it, again fasten to the board with unfinished side up, and again dress down. Before removing from the board, lay out the curved end to correspond with the curve of the head, and cut to line with a chisel.Remove from board, finish curved end with sand-paper block. Bore hole h for hanging up, locate holes for screws, and drill just large enough to allow ¹/₂-inch round-head brass or blued screws to pass through. In attaching the head, make sure that the two parts are at right angles, and use thin copper burrs or washers under the screw heads.

If the blade is to have edges of a different colour, joint the maple on shooting board, and glue the strips to it, before planing to thickness. This should be done on a flat board, with paper between it and the blade. Glue the three pieces together, and drive 1¹/₄-inch brads up close to and touching the outside strips, at intervals of four inches. By bending these slightly over the blade, considerable pressure will be obtained, tending to keep the pieces together while glue is hardening.

Then proceed to dress down, and true up as before. When the process is once learned, considerable pin money may be made by disposing of the squares, and that will help to buy material for other things.

Triangles made from single pieces of wood are absolutely unreliable. Referring to Fig. 207, the 45-degree triangle shows the grain running up and down. As shrinkage takes place m will not change, but n will, and this will alter the angles; and besides a piece of thin wood this size will warp and make the triangle useless for mechanical drawing.

The 30-60 triangle illustrates the usual method of constructing a wooden triangle.

Aside from bisecting the 90, 60, and 30 degree angles to get the mitres, these joints, if simply glued, will be too weak for practical use. The edge view and dotted lines indicate a thin feather of wood glued into a saw cut made through the edge of each corner, the usual method of strengthening. It is a delicate operation, and is only recommended to boys who are fond of fine work.

A very serviceable section liner may be made from a wooden triangle by carefully cutting out of one side a rectangular opening, as shown in the detail. Make a piece of thin wood to fit this space, but ¹/₈-inch shorter, and fitted so as to move freely. By moving this block and the triangle, alternately, vertical or oblique lines can be drawn for sectioning, and they will be equally spaced. Other blocks varying in length will give a variety of spacings.

It is possibly one of the cheapest section liners, and the most satisfactory within the means of any one. Irregular or French curves may be made in thin wood. They should be drawn on the surface, sawed out with the coping saw, and sand-papered smooth. As their thickness should be but a trifle over ¹/₁₆ inch, they are very frail and easily broken. These curves can be easily made in sheet aluminum, and they will be much more satisfactory. This metal is handled similarly to thin wood, except that the saw must be a metal cutting blade.

Triangles may be made of the same material. Lay out the form with a sharp steel point or scriber, saw as close to lines as possible, and with a fine file finish to line. Then smooth the curves with fine emery paper wrapped around a lead pencil. To make straight edges, as on triangles, lay a sheet of emery cloth on bench, and rub triangle back and forth.

THE PANTAGRAPH

For copying designs, for reducing or enlarging, this old-fashioned instrument may be easily constructed. Fig. 208 shows it made of four strips of thin wood of equal length. Either pine or white wood will answer. The pieces have to be squared, twenty-five inches long, three quarters of an inch wide, and a quarter inch thick.

Bore or drill through the four pieces held in a vise, and space the holes shown in drawing three inches apart, ¹/₈ inch in size.

When put together, a, b and c should be in line. Point a is to remain fixed, the pantagraph being free to move around it as a pivot. To accomplish this, cut out a block, as shown at x, with a hole drilled at the centre for pivot, and two others for screwing to the drawing table or board.

The pin for this pivot may be a thick flat-head wire nail, screw, or even a screw eye. The joints d, e, and f are also pivots moving with the pantagraph. They may consist of thumb screws, and nuts, or screw eyes, and must move freely, yet without play.

Points b and c are to be interchangeable, one having a tracing point, the other a pencil.

The tracing point may be a wire nail, rivet, or screw, with the point filed sharp, and then slightly rounded. The pencil point should be a piece of lead pencil, whittled down to such a size as to pass through the hole at b and c, and make a snug fit.

To enlarge a design, place tracing point at b, and fasten original design under it to drawing board with thumb tacks.

Under c fasten a sheet of drawing paper. With the right hand at b, trace the design by carefully sliding tracing point along the lines. At the same time, with the left hand keep pencil point at c sufficiently in contact with the paper to make a clear line.

To reduce a drawing, reverse b and c, bringing pencil point and paper to b, and original to c. Pass tracer over design at c, and the reduced design will be traced at b. Different proportions between original and reproduction may be obtained by shifting the position of pivots e and f.

Fig. 208 shows pivot e shifted to position h. As distance c e should always equal distance d f, it now becomes necessary to move pivot f to point g. By remembering this rule, and placing pivots in various positions, a wide range of proportions is possible.

THE DRAWING TABLE

A table to hold the drawing board should be not less than 3 feet 2 inches high, as much of the work is performed standing up. A stool with revolving seat should be provided for the draughtsman to sit on occasionally.

The table top may be made slanting, but it is better practice to have a heavy flat top of pine, which may be used as a large drawing board itself, and to provide for the slant by using a triangular block under the farther end of drawing board. Two or three blocks may be made, about two feet long and of different sizes, to give different degrees of slant.

Tables for this purpose are often made with tops, which may be adjusted at different angles, and the young designer may try his inventive talent in this large field, but any arrangement which will bring an element of instability is to be studiously avoided. The drawing table should be as solid and rigid as possible.

The design in Fig. 209 was made by our boys, and has proved very satisfactory. It has much of the mission style about it, with its square legs and mortised joints.

After the description of mission furniture construction in previous chapters, only a few points in the construction need be mentioned.The board a, used as a foot rest, is necessary when sitting at the table on account of its height, and it also ties the frame together in the front. The cross rail b acts in the same capacity at the back.

The heavy pine top is "built up" like a drawing board of several pieces, and supported by two cleats 3 × ¹/₈ inches across the grain underneath. It may be attached to the frame by any one of the methods described under mission furniture, and its left-hand edge should be as true as that of the drawing board.

If an especially accurate edge is desired, a piece of iron 1 × ¹/₄ inch, planed straight by a machinist, may be let into this edge, as shown in the drawing, and secured by flat-head screws through holes drilled and countersunk. This arrangement is seldom seen, but it is well worth the added cost.

The table shown is provided with a generous-sized drawer. This may be omitted, but is a great convenience for keeping plans and sketches. Its construction is shown in detail. The sides and front have a ¹/₄-inch groove, ploughed to receive the bottom, and at the back end a vertical groove is cut to hold the back piece which is dadoed to fit.

At the top of each side is nailed a strip ⁵/₁₆ inch square. These cleats are to retain the strips s. Make these strips s of hard wood, preferably ash, and about ¹/₁₆ inch longer than the width of drawer, measured inside.

By placing the strips on top of drawings obliquely, and then straightening them across the drawer, they bind against the sides, and keep drawings down flat. The cleats at top of drawer prevent them from escaping at the top, especially when it becomes nearly full.

The extra front on the drawer with rounded edges covers up the joints around front of box, and is a purely ornamental feature. If this is used, secure to real front by flat-head screws from the inside.

The box which holds the drawers is to be secured to the legs by screws countersunk. Many modifications of this table will occur to the woodworker, such as additional drawers, but it must be kept in mind that comfortable knee room is essential, and the space on under side of the top is largely to be reserved for this important purpose.

A box for holding instruments has been described in another chapter, and triangles, rules, etc., may be kept in it.

The T square should be hung on a hook at either end of table, to overcome any tendency the thin blade may have to twist or warp, the weight of the head helping to draw it out straight.

All drawings should have a neat title, and a number. To work out a system of numbering so that any drawing may be found quickly is a good job for a rainy day.

A good filing cabinet for plans is suggested in Fig. 210. Dimensions are not given, as they will depend on the size of drawing paper used. A uniform-sized sheet should be adopted at the start, and the drawings scaled to accommodate this size of paper.

The shelves should be ¹/₄ inch thick, and gained into sides as shown. A clear space of 1¹/₂ inches between the shelves will be ample, and a semicircular curve should be cut in the front. The depth of cabinet should not be over half an inch more than the width of the sheets.

A top and mitred base are shown, and the space between should be closed by a panelled door to keep out dust.

A cabinet of this style should not be less than thirty inches high, and if the whole space is not required for drawings, the lower part may be changed and fitted with drawers for models, specimens, and other treasures.For boys who are interested in collecting, whether minerals, butterflies, or other things, such a cabinet may be made entirely of drawers, and the panelled door omitted.

For the safe keeping of butterflies, moths, and other insects, an eminent scientist has recommended a drawer construction as shown at Fig. 211. This detail shows a section at the front, with the bottom piece gained into a groove. The bottom of the drawer is covered with a layer of sheet cork, and over it oiled paper. The upper part of box is not fastened, but is slipped down inside strips s, which have rounded tops, and extend around the four sides.

The upper half is grooved to receive a sheet of glass, which is held in place by a small cleat. By this method the drawer is covered while the specimens are visible, and dampness is kept out. The cork bottom is to receive the pins, and the specimens may be reached by simply taking out the top. The dimensions recommended for the drawer are 22 × 16 × 2 inches, outside measurements, and if a number are to be used, the spaces between the shelves of the cabinet should correspond with these figures.A quaint conceit sometimes used by enthusiastic collectors is to make their boxes in the form of books, as shown at a (Fig. 212).

The outside has the shape of a book, the two halves being fitted by tongue and groove joint. This keeps out moisture, the great enemy of dried specimens, and when a number of these boxes, properly coloured and labelled, are piled on a shelf, they have the appearance of so many large volumes.

This unique idea may be used in other ways. A very pretty illustration is a stamp box for the writing desk, made up in the form of a book, which apparently has a silk ribbon for a book mark. This ribbon is the handle of a little drawer, which pulls out, disclosing the contents. The arrangement is shown at b. The idea may be carried still farther by having half a dozen of these small volumes in a book rack, the labels reading—"rubber bands," "pens," "stamps," etc. All should be stained a uniform colour, and the illusion may be carried still farther by gilding the parts which represent the edges of the leaves.