In Fig. 187 the lower row of numerals indicates the number of times (in
diameters) the original is enlarged when all four holes similarly figured
are used; the upper row, the size of the copy as compared with the original
in case of reduction.
If proportions other than those given are required, a very little
calculation will locate the necessary holes.
Pivots.--All the pivots must fit their holes accurately, as any looseness
at the joints detracts from the truth of reproduction. For pivots band b
and e may use brass screws and small pieces of hard wood as nuts to hold
them in position. The nuts should screw on rather stiffly, and not be
forced hard against the rods, as free motion with little friction at all
joints is essential for good work.
[Illustration: FIG. 187.--Diagram showing how to mark off pantograph
rods. The dotted lines above rod give distances of holes from ends.]
The fixed pivot at a may be merely the shank of a wire nail of the proper
size driven into the board, a cork collar being slipped over it to keep the
rod the proper distance from the board. For c use a screw to the head of
which has been soldered half an inch of a round-headed brass nail, which
will move easily over the paper.
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