Drill Jigs Principles of Design Machinery ... - Evenfall Studios

PRINCIPLES OF DRILL JIGS
of the upright shown in Fig. 21, rather than on the opposite side, as
that does away with any tendency of the jig to tip when pressure is
applied in the operation of drilling.
Leaf Drill Jigs
For many kinds of work a jig provided with a leaf, as shown in
Fig, 22, gives best results, as the leaf may be raised, and the work
removed, and any dirt cleaned from the working surfaces. After
placing the piece to be drilled in the jig, the leaf is closed. As the
bushings are in the leaf, it is apparent that it must always occupy
the same relative position to the work for the different pieces, or they
will not be duplicates; consequently, the fulcrum pin, a, must be a
perfect fit in the hole in the leaf, and a locating -pin & is provided to
prevent any tendency of the leaf to move from the action of the drill
when cutting. Jigs provided with such a pin show less tendency to
wear in the joint. The leaf should not close down onto the work, but
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