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

34 No. 3 DRILL JIGS
many operations in the shop, however, permit of so wide a limit of
error that fairly accurate jigs can be designed which, having a certain
degree of flexibility, will accommodate a variety of work. These jigs
are valuable in a double measure. In the first place they save a great
deal of outlay for individual jigs, and, secondly, many a little job,
for which no individual jig would be warranted, may be drilled in an
adjustable jig at a great saving of time and gain in accuracy.
The jig shown in Fig. 46, in use in the W. F. & John Barnes shops,
Rockford, 111., is designed with the purpose of securing adjustability,
so as to adapt the jig to pieces of different shapes and dimensions. The
base piece A supports an upright F, to which the knee, E, is bolted.
This knee holds the drill bushing and is tongued and grooved to the
Jndwitrial Pres,y.y.
Fig. 46. Adjustable Drill Jigr
upright so that it may be raised or lowered for work of different
heights. The work is held by two slides, B and (7, and a set-screw D.
The lower slide, C, has a tongue fitting in a groove in the base, and
one end is V-shaped to give support to the lower end of the work,
against which it is made to bear. The slide B has a tongue fitting
in a groove in the top of the lower slide, and may thus be adjusted in-
dependently of the latter.
An adjustable jig also provided with an indexing feature, is shown
in Fig. 47.. This jig is intended for drilling the clearance holes in
small threading dies. As these holes are located on different distances
from the center according to the diameter of the thread the die is intended
to cut, one jig would be necessary for each diameter of thread
in the die, although the outside dimensions of the die blanks are the
same for wide ranges of diameters of thread. To overcome the neces-
sity of so many individual jigs, an adjustable strap or slide C is pro-