very simple and inexpensive type, so constructed as to allow of the rapid locating and fastening of the work and the removal of the same when finished. The casting as drilled is shown in two views in Fig. 53, and has two holes A B drilled in each of the

eight arms.

Before being drilled the castings are chucked in the turret-lathe, and the centre hole C is bored and reamed to size, and the hubs are faced.

The jig Fig. 50 consists of two castings, of which J is the body casting and T the lid. There were openings at all sides for the escape of the dirt and drillings. The legs L on four sides and those at M M on back are finished and scraped, so as to be dead square with each other. The face of the body casting is also squared with the sides, so that the lid will rest squarely on it. Two dowel-pins U U locate the lid, and the thumb-nuts V Vare for fastening it. A stud of tool steel, which is threaded at both ends and its largest diameter finished to fit snugly the centre hole C, is let into the bottom of the body casting, as shown at O, and held rigidly in position by a nut P at the back. A large hole is bored in the centre of the lid, so as to clear the nut Q. The sideway locating-point is at R. It consists of a Stub steel pin, which is hardened and driven into the body of the jig. set-screw 8 is also hardened and let in through the projecting

The

lug, and is used for forcing the work against the locatingpin R.

The four bushings X are let in as shown, and the manner of locating and finishing the holes was as follows: The body casting was strapped to the table of the universal milling-machine, and

the centre of each hole was located, and the hole was finished in turn by the use of a Brown & Sharpe height-gauge for locating, measuring from one side of the jig and from the miller-table, and using a sharp end, mill for finishing, first drilling the hole with a drill about-inch under size.

The four holes for the bushing W were located by the "button method," as described in Chapter III. After being located, the four holes were drilled and finished to size by strapping the lid on the lathe face-plate and locating each button to run true by the use of an indicator.

When using the jig, the lid T was removed by unscrewing the thumb-nuts V, and the casting to be drilled was located on the centering-stud 0, the faced hub of the work resting squarely on the finished boss N. One of the angular-faced projections of the work is then forced against the locating-pin R by tightening the set-screw S. The nut Q is then fastened securely within the jig, as shown by the dotted lines in the plan view of the jig. The holes B in the projections are then drilled through the bushings X, that is, through every other one of the projections, by standing the jig on each of the four pairs of legs L in turn. The jig

is then rested on the legs M and four of the holes A are drilled

through the bushings W. The lid of the jig is then removed, and the nut W and the set-screw S loosened. The work is then moved and located so that the holes A and B in each of the four remaining projections may be drilled. The operations of locating and fastening the work and then of drilling the holes are repeated.

As can easily be seen, the design and construction of this jig is of the simplest possible character consistent with accurate and rapid production. Although it is necessary to locate the casting twice, the time entailed amounts to very little, and is fully compensated for when the simplicity and cheapness of the jig are considered, as in order to drill all the holes in one operation a far more complicated jig would have been necessary.

In Figs. 51-52 are shown views of a jig of a rather more elaboate and complicated design than the first. It is used for drilling the holes in the casting Fig. 53, and finishing the hubs-that is, the three holes G and the hole through each of the lugs F, the hole through the hubs at I and the finishing of the hub at H. As shown in the two views of the jig, the work is located at three points at each of the finished projections or lugs J, locating within the parts D, which are drilled to size in a preceding oper

ation. The work is located sidewise against the two adjustable stops K, by tightening the two set-screws Q against the work. The lid E of the jig is hinged within the body casting at F by the pin G. Legs are cast on two sides and on the bottom of the body casting, as shown at B and C respectively. The four

bushings L are for drilling the holes through the lugs F, and those at M, in the lid, for drilling the three holes G. The method used for fastening the lid while the work is being drilled is by means of a swinging-stud and a nut and washer I, the stud being hinged to swing free in the body casting at H, a slot being let in it and in the lid for that purpose. Two set-screws P are let into the lid for locating and fastening the work within the jig. The two large bushings O, for use when finishing the hubs, are permanently located within the lid, while those for drilling the hole I in the hubs are inserted within them when in use. When using the jig the work is located and fastened within by the setscrews Q and P, and all the holes are then drilled. The two bushings N are then removed, and the hubs are faced and reduced to size. The fastening set-screws are then released, the swinging-stud I is thrown back, and the lid raised, after which the work is removed.

All the various parts of both these jigs, including the castings, are made sufficiently heavy and strong to withstand all strain to which they may be subjected when in use. The manner of locating the work is such as to be positive, and without the possibility of shifting during the operation of the tools. The means and points chosen for the fastening of the work within the jigs are such as to be rapid to manipulate, and in no way to interfere with the drilling; and, lastly, the design and construction of both jigs are such as to dispense with all unnecessary parts and labor.

JIG FOR DRILLING ROUGH CASTINGS IN PAIRS.

Fig. 56 shows two views of a drill-jig, with work in position for drilling holes in the tops of rough pairs of bracket castings. These castings were used in large numbers and were of the shape shown in Fig. 55. The three holes in the body portion were cored, and, as the pairs were not machined at any point before drilling, the holes were used as locating-points in the jig. The jig consists of a body casting in the shape of an inverted "T," X being the base and G the upright which supports the plate E and the work. The work is located in pairs on either side of the

upright by the dowel-pins D D D, which enter the cored holes and are held by the clamping device, a cross-section of which is shown in Fig. 57. This clamp is of tool steel, with wings at I

and J to swing over and clamp the work, the centre portion L being turned to fit the semi-circular bottom of the slot in the upright G. A plate H is let into and fastened to the front of the upright G by the two screws N N. This plate has a stud M fastened in the centre of it, in line with the circular portion L of the swivel-clamp. The face of the stud is finished to the same radius as the portion L and is of a length sufficient to allow of the face acting as a back bearing for the swivel-clamp to swing on.

This construction allowed of making the clamp in one piece, and gave better results than if one of the wings had been made separate. About clearance was given lengthwise to the circu