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.
[Illustration: 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.