Fig. 1693.
Referring especially to [Fig. 1693], a1 and a2 are the two wings of the bed plate, each being provided with V-slides to carry the uprights or standards b1, b2, on each of which is a drilling head c1, c2, these being each adjustable vertically on its respective standard by means of rack and pinion and hand wheels d1 and d2. The heads are balanced so that the least possible exertion is sufficient to adjust them. The vertical standards b1 and b2 are provided at their bases with a gear wheel operated by means of pinions at g1, g2, so that they may be rotated upon the sliders e1 and e2, by means of which they may be traversed along their respective bed slides. The drilling heads are composed of a slider on a vertical slide on the face of the vertical standard or upright, rotary motion and the feed being operated as follows: Power is applied to the machine through the cones k1 and k2, working the horizontal and vertical shafts l1 and l2, &c. On the vertical shafts are fitted coarse pitch worms sliding on feather keys, and carried with the heads c1 and c2, &c. The worms gearing with the worm-wheels m1 and m2 are fitted on the sleeves of the steel spindles n1 and n2. The spindles are fitted with self-acting motions o1 and o2, which are easily thrown in and out of gear.
The shell to be drilled is placed upon the circular table h, which is carried by suitable framework adjustable by means of screw on the V-slide i, placed at an angle of 45° with the horizontal bed plates. By this arrangement, when the table is moved along i it will approach to or recede from all the drills equally. j1 and j2 are girders forming additional bearings for the framework of the table. The bed plates and slides for the table are bolted and braced together, making the whole machine very firm and rigid.
The machine is also used for turning the edge of the flanges which some makers prefer to have on the end plates of marine boilers. The plates are very readily fixed to the circular 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 r1 and r2. 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 s1 and s2, 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 r1 and r2 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 ft. 3 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.
As to the practical results of using the machine, the drills are driven at a speed of 34 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 11⁄8 in. in diameter, can be drilled in about 21⁄2 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 ft. diameter), is about 21⁄2 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 ft. 6 in. in diameter, the plate being 11⁄8 inches thick, is three hours. Of course, if several boilers of one size are being made at the same time, the holes in two or more of these plates can be cut out at once. The machine is of such design that it can be placed with one of the horizontal bed plates (say a1) parallel and close up to a wall of the boiler shop; and when the turning apparatus is being used, the vertical arm b2 can be swivelled half way round on its square box e2, and used for drilling and tapping the stay holes in marine boiler ends after they are put together; of course sufficient room must be left between bed plate a2 and the wall of boiler shop parallel with it, to allow for reception of the boiler to be operated upon.
In [Figs. 1694] and [1695] is represented a machine which is constructed for the drilling of shells of steam boilers, to effect which the boiler is set upon a table, round which are placed four standards, each carrying a drilling head, so that four holes may be drilled simultaneously, and is provided with a dividing motion that enables the table to be revolved a certain distance, corresponding to and determining the pitch of the rivet holes.
It is capable of drilling locker shells of any diameter between four and eight feet. The feed motion to each drill is driven from one source of power, but each drill is adjustable on its own account. The depth of feed is regulated by a patent detent lever which engages with the teeth of a ratchet wheel, till released therefrom by contact with the adjustable stop. The drill spindle is then instantly forced back by the spiral spring and the forward feed motion continues.