table H, and the edge of the
flange trued up much quicker than by the ordinary means of chipping.
When the machine is used for this purpose, the cross beam P, which is
removable, is fastened to the two upright brackets R 1 and R 2. The
cross beam is cast with $V$ slides at one side for a little more than
half its length from one end, and on the opposite side for the same
length, but from the opposite end. The $V$ slides are each fitted with a
tool box S 1 and S 2, having a screw adjustment for setting the tool to
the depth of cut, and adjustable on the $V$ slides of the cross beam to
the diameter of the plate to be turned. This arrangement of the machine
is also used for cutting out the furnace mouths in the boiler ends. The
plate is fastened to the circular table, the centre of the hole to be
cut out being placed over the centre of table; one or both of the tool
boxes may be used. There is sufficient space between the upright
brackets R 1 and R 2, to allow that section of a boiler end which
contains the furnace mouths to revolve while the holes are being cut
out; the plate belonging to the end of a boiler of the largest diameter
that the machine will take in for drilling. The holes cut out will be
from 2 feet 3 inches in diameter and upwards. Power for using the
turntable is applied through the cone T. The bevel wheels, worms, worm
wheels, and pinions for driving the tables are of cast steel, which is
necessary for the rough work of turning the flanges.

[Illustration: Fig. 299. (Page 275.)]

As to the practical results of using the machine, the drills are driven
at a speed of 340 feet per minute at the cutting edges. A jet of
soapsuds plays on each drill from an orifice 1/32 in. in diameter, and
at a pressure of 60 lbs. per square inch. A joint composed of two 1-inch
plates, and having holes 1 and one-eighth in. in diameter, can be
drilled in about 2-1/2 minutes, and allowing about half a minute for
adjusting the drill, each drill will do about 20 holes per hour. The
machine is designed to stand any amount of work that the drills will
bear. The time required for putting on the end of a boiler and turning
the flange thereon (say 14 feet diameter) is about 2-1/2 hours;
much, however, depends on the state of the flanges, as sometimes
they are very rough, while at others very little is necessary to true
them up. The time required for putting on the plate containing the
furnace mouths and cutting out three holes 2 feet 6