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.
Fig. 208. The pantagraph
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.