At d is needed a hollow pivot, fashioned
out of a quarter of an inch of pencil-point protector or some other thin
tube, burred over slightly at the ends so as not to fall out. The end of B
at f has a slotted hole to grip the pencil or pointer, as the case may
be.
A Same-size Pantograph.--For making a same-size copy, tracing may be
preferred to the use of a pantograph; but if a pantograph is adopted, a
special apparatus may be constructed for the purpose. The arrangement is
exactly the same as that already described, excepting that the only holes
needed are those at a, c, d, f, at the middle points of the four rods, the
parallelogram formed by the rods being equal-sided. The fixed pivot is
situated at d, and pencil and pointer holes are made at a and f.
Using the Pantograph.--When adjusting the instrument for reduction or
enlargement, make sure that the adjustment pivots are in the holes
corresponding with the scale. The fixed pivot, pointer, and pencil must be
rigid, and, with pivot c, be of such a length that the pantograph as a
whole moves parallel to the paper. A little sliding weight to place on the
rod near the pencil will be found useful for keeping the pencil point in
constant contact with the paper.
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