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

30 No. j DRILL JIGS
to one side about the hand screw G. When the collar has been put in
place the clan?p is swung back, and in doing so, its motion is limited
by the pin F, which brings it to a stop directly over the collar. At
the top of the jig is a bushing B through which the drill is guided.
When the outside diameter of the collars is likely to vary, the pins
/), D, D, may be replaced by a central pin, L, as shown in the separate
view in the cut, and the collar held on this while it is being drilled.*
The jig shown in Fig. 43 is designed for drilling the holes in the
center of collars, and the method of drilling, described below, also sug-
gests the value of systematizing the work in using jigs. The collars
to be drilled are made of annealed tool steel in sizes varying in thick-
ness as well as in diameter and size of hole, and are cut off from the
t? Industrial
Fig. 42. Jig for Drilling Set-screw Holes in Collars
Prttf, ft. Y
bar on the cold saw. There being a three-spindle gang drill in the
shop, which was idle part of the time, it was decided to make use of
it in the production of these collars. Four jigs like the one shown in
the cut were made. They were made to take any diameter or thickness
of collars within their range. The body of the jig is a square block of
steel, with the hole to receive the collars exactly in the center. The
lower end is threaded left-hand to receive the piece B, which has a
square hole in the center to receive the wrench C. The ring D Is
bored taper, and fits the collar operated upon at the top end only, so
that the collars will drop out of the jig easily. Different rings are
made to fit collars of different diameters, and are just an easy drive
fit in A, the body of the jig. They are driven out with a soft punch
through hole E in piece A. Drill bushings F are also interchangeable.
Piece G is a distance piece used when drilling thin collars in order to
avoid screwing piece B into the jig too far. It is apparent from the
cut that these pieces are made to fit the collar at one end, and beveled
at the other to center in piece B. The reason piece B is threaded
left-hand is as follows: If the collar operated upon should turn in
C. H. Rowe, January, 1903.