Fig. 297.

Fig. 298.

The wax process is, however, more suitable for engravings in plain outline only, and is especially excellent when the parts are small and the lines fall close together; as, for example, in Figures 298 and 299, which are engravings of a boiler drilling machine, and were produced for the American Machinist by tracing over a wood engraving from London, "Engineering" in the manner already described. The fineness and cleanness of the lines in the wax process is here well illustrated, the disposition of the parts being easily seen from the engraving, and easily followed in connection with the following description:

The machine consists of two horizontal bed-plates A 1 and A 2, made with V slides on top, and placed at right angles to each other. Upon each of the bed-plates is fitted a vertical arm B 1 and B 2, each of which carries two saddles, C 1 and C 2, these being each adjustable vertically on its respective arm by means of rack and pinion and hand wheels D 1 and D 2. The saddles are balanced so that the least possible exertion is sufficient to adjust them. The vertical arms, B 1 and B 2, are cast each with a round foot by which the arms are attached to the square boxes E 1 and E 2, which are fitted to the V slides on the horizontal beds A 1 and A 2, and are adjustable thereon by means of screw and ratchet motion F 1 and F 2. Each of the square boxes has cast on it a small arm G 1 and G 2, carrying studs upon which run pinions gearing into the circular racks at the foot of the vertical arms. The square boxes have each a circular groove turned in the top to receive the bolts by which the vertical arms are connected to them, and thus the vertical arms, and with them the drill spindles N 1 and N 2, are adjustable radially with the boiler - the adjustment being effected by means of the pinions and circular racks. The pinions are arranged so that they can be worked with the same screw key that is used for the bolts in the circular grooves.

The shell to be drilled is placed upon the circular table H, which is carried by suitable framework adjustable by means of screw on a 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. J 1 and J 2 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. Power is applied to the machine through the cones K 1 and K 2, working the horizontal and vertical shafts L 1 and L 2, etc. On the vertical shafts are fitted coarse pitch worms sliding on feather keys, and carried with the saddles C 1 and C 2, etc. The worms gearing with the worm wheels M 1 and M 2 are fitted on the sleeves of the steel spindles N 1 and N 2. The spindles are fitted with self-acting motions O 1 and O 2, which are easily thrown in and out of gear.

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 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.

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 in. in diameter, the plate being 1 and one-eighth in. 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 A 1), parallel and close up to a wall of the boiler shop; and when the turning apparatus is being used, the vertical arm B 2 can be swiveled half way round on its square box E 2, 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 A 2, and the wall of boiler shop parallel with it, to allow for reception of the boiler to be operated upon.

It would obviously be quite difficult to draw such drawings as in Figures 298 and 299 on thin paper, so as to enable the drawing to be traced on the wax direct by the process before described, unless indeed the draftsman had considerable experience in fine work; hence, it is not uncommon to make the drawing large, and on ordinary drawing paper. The engraver then has the drawing photographed on the surface of the wax, and works to the photograph. The letters of reference in wax engravings are put in by impressing type in the wax, and in this connection it may be remarked that the letters I and O should not be used on drawings to be engraved by the wax process, unless they are situated outside the outlines of the drawing, because the I looks so much like part of a dotted line that it is often indistinguishable therefrom, while the O looks like a circle or an ellipse.