hole was drilled in the pin X for the spring cross-pin. After the handle Z was made all the parts were assembled. All that remained to complete the rig was the boring-bar, Fig.

The bar was small
Two sets of cutters

239, and the two sets of cutters B B and D. This bar
was of machine steel, turned taper at the end to fit the
drill-press spindle, and for the rest of the length a run-
ning fit in the bushings U and V.
enough to clear the cored holes.
were made, one set for roughing and the other for finish-
ing. These cutters were fastened in the bar by taper-
keys. The jig was strapped to the table of a large
drill-press. The index-plate N, with the pin X in one
of the notches, was clamped and a casting to be bored
clamped in position on it, so that the boring-bar would
be as nearly central as possible in the cylinder to be
bored. The roughing-cutters were then fastened in the
bar and the holes were bored. These cutters were then
removed and the finishing pair were substituted and the
holes were finished.

The Boring Bar

B

FIG. 239.

After all six holes were bored, which required only three adjustments of the index-plate, both ends of all six cylinders were faced by using the cutters D. All the eastings, of which there

were a large number, were bored and faced in this manner, and were found, when assembled with other parts, to interchange perfectly.

DRILL-PRESS BORING RIG FOR INTERCHANGEABLE WORK.

The tools described in the following were used for boring and finishing the cast-iron shell shown at B, Figs. 242-243. The part finished is shown at F, being a seat for a brass ring that was to fit in snugly so as to be air-tight, and it was also necessary to have them all exactly the same size. The shells were being made in lots of five hundred.

The jig for holding the shells is also shown in the two views. A is the jig, of cast-iron, which was faced off on the bottom and

strapped true on the face-plate of the lathe by the ears E E. It was then bored out to the shape and size of the shells at C and a hole bored in the bottom for the plug D. It was then milled out at three places on the top to give the three wings D clearance. The plug D, made of machine steel, was then turned and finished so as to just fit the inside of the shells, as shown, and then driven into the jig A, projecting through at the bottom, as shown. The part projecting through just fitted the centre hole in the table of the large drill-press in which the boring was done.

Figs. 240 and 241 show the holder and tools for boring, which were made in the following manner: G is the holder proper, made of cast-iron with three wings, to allow of using three cut

ting-tools, as we found after experiment that this number worked the best. The tool was first chucked and the hole I bored and reamed for the shank J. It was then removed and the shank J turned and finished to fit the spindle of the drill-press, with a shoulder at M. The other end was turned down so as to drive

snugly into the holder G. The assembled tool was then put between centres in the milling-machine and the holes for the tools KK K were laid out and drilled and reamed. It was then taken out and the holes for the set-screws LLL were drilled and

tapped. Next, the three cutting-tools were made and finished as shown. These were hardened and drawn, and inserted in their places, which completed the boring-tool.

A piece of steel the size of the hole in the table was chucked in the drill-press and inserted in the hole in the table, which was

locked, thereby setting it true with the spindle. The jig A was strapped on the table by the ears EE, with the lug D in the centre hole, and the work put in, resting on the bottom as shown in the sketch. The plug D centred it and the three pins not shown entered the holes in the ears B, which prevented it from truing. The holder, Fig. 240 was then set into the spindle and the tools set to cut exactly the right diameter, and after being run down to the proper depth the spindle-stop was set.

The rest was plain sailing and, except for stopping to sharpen tools at long intervals, the pieces were turned out very rapidly (each and every one alike) at a very small cost and much better and cheaper than they could have been done by any other practical means. The saving in the first one hundred shells paid for the cost of the tools.

A SPECIAL MACHINE FOR BORING BRACKETS AND SPINDLE-HEADS.

When constructing sensitive drill-presses of from one to five spindles, the boring of the hole for the spindle in the upper bracket and the spindle-head is done after all the other work has been done and the upper column, upper bracket, and spindlehead assembled. In the following, Figs. 244 to 247, I show and describe a machine which was designed specially for doing this work that is, for boring the spindle holes in drills of from one to five spindles.

As this tool or machine is designed to be used and fastened directly to the columns while the holes are being bored, the pos sibility of error in the alignment of the spindle when assembled is reduced to a minimum; also, the manner of locating and fastening the tool to the work while in operation is as reliable and positive as could very well be devised for the class of work for which it is used. The tool consists of, first, a body casting K of the shape and design shown in Figs. 244, 245, and 246. The driving-spindle Y, with a tight and a loose pulley, Wand W W respectively, at one end, and a bevel-gear V at the other. the head is the spindle-driving gear with the two drivingpins RR; O is the spindle or cutter-bar, and S the bar-driver,

while I is the means for feeding the pinion, which engages the rack, on the bar or spindle. The sets M M M M in the lugs which project above the face of the plate or body casting shown, are for bracing and holding securely the brackets and heads

while they are being
bored. PP, in the spin-
dle O, are the cutters,
while the adjustable
angle pieces J J, and
the clamping-levers L L,
are for fastening the rig
true and positively to
the columns while in operation.

The means and ways called into use in the construction and successful operation of the boring rig are of interest and they will be described in turn. After the body casting A was secured, the first thing done was to bore and finish the hole through the head B and the tail O. The size of the hole in the head B is shown clearly in the detail drawing in Fig. 247. The boring was accomplished by strapping the casting lengthwise

on an angle-plate, which, in turn, was fastened to the table of the large drill-press-first drilling a clearance-hole through both head and tail large enough to allow of the boring-bar (used for finishing), being entered through both the head B and the tail C, get