Modern Machine-Shop Practice Part 198

[Ill.u.s.tration: Fig. 2995.]

[Ill.u.s.tration: Fig. 2996.]

[Ill.u.s.tration: Fig. 2997.]

[Ill.u.s.tration: Fig. 2998.]

[Ill.u.s.tration: Fig. 2999.]

The several sections are now ready to be welded together for the complete frame, these welds being made as follows: The ends are upset as in Fig. 2994 to receive on each side a [V]-piece such as in Fig. 2995, which is heated on a porter-bar, and is of a more acute wedge than the ends to be welded, so that when laid in as in Fig. 2996 it will touch at the bottom first, and thus allow the air and whatever dirt there may be on the surfaces to squeeze out as the welding proceeds. The method of heating the frame for these welds is as follows: The [V]-block (which has the grain of the iron running in the same direction as that of the frame) being heated in the blacksmith's forge, the frame is clamped together and counterbalanced by means of weights, so that it may be laid over a fire pot, constructed as in Fig. 2997. This fire pot is lined with brick, and has its blast supplied through a piece of flexible tube.

The anvil is of cast iron, shaped as in Fig. 2998, and placed on the other side of the frame and opposite to the fire pot or portable forge, as shown in Fig. 2997, so that the frame, when the heat is ready, may be turned over upon the blocks on which it rests, and the part to be welded will come upon the anvil. After one side is welded the anvil and the portable forge change places, and the second side of the weld is made.

In the following figures (which are taken from _Mechanics_) is ill.u.s.trated the method employed to build up the shaft shown in Fig.

3001, which was for the steamer _Pilgrim_. Forgings of such large dimensions are built up of pieces or slabs, called blooms, which are themselves forged from sc.r.a.p iron, which is piled as in Fig. 3000. For the forging in question this sc.r.a.p iron consisted of old horseshoes, boiler-plate clippings, boiler rivets and old bolts, and the first step in the manufacture is to form this sc.r.a.p into piles ready for the furnace.

[Ill.u.s.tration: Fig. 3000.]

[Ill.u.s.tration: Fig. 3001.]

[Ill.u.s.tration: Fig. 3002.]

[Ill.u.s.tration: Fig. 3003.]

These piles are made upon pieces of pine board 1/2 inch thick by 16 inches long by 10 inches wide. On these the sc.r.a.p is piled about 14 inches high, each pile weighing about 270 pounds. After piling, the sc.r.a.p goes into the furnace and is raised to a welding heat, the board retaining its form as a glowing coal almost to the last. The pile of sc.r.a.p is heated so nearly to melting as to stick together enough so that it can be picked up in a long pair of tongs with peculiarly-shaped jaws, and, as these tongs are suspended by a chain from an overhead traveller running on an iron track, the bloom is easily transferred to the anvil of the steam hammer, where, after one or two blows, a small porter-bar with a crank end, such as shown in Fig. 3003, is welded on, and the pile is rapidly drawn out into a square bar. When completed the porter-bar is cut off, and the bar is laid aside to cool. The pile of sc.r.a.p has now become a "bloom," such as shown in Fig. 3002, and has been reduced in weight from 270 lbs. to 240 lbs. The bloom is about 30 inches by 5 inches by 5 inches in dimensions, and has rounded, ragged ends, and a surface full of lines marking welding of the individual pieces, and at the ends looking as though the sc.r.a.p had united by melting rather than by any welding process.

[Ill.u.s.tration: Fig. 3004.]

These blooms are then taken to the large steam hammer and furnace by which the shaft is to be built up. The porter-bar, although merely a tool whereby to handle the ma.s.s, forms practically a base wherefrom to build up the shaft. The construction of the furnace is shown in Fig.

3004, the heat, after pa.s.sing the work being used for the steam boiler that supplies steam to the steam hammer.

The porter-bar is held by a crane, the chain being placed in such position in the length of the porter-bar as to balance it. On the end of the porter-bar is a clamp, having arms by which the bar may be turned in the furnace and when under the hammer.

Fig. 3005 represents the bar in position in the furnace, the aperture through which it was admitted having been closed up by bricks luted with clay, one brick only being left loose, so that it may be removed to examine the heat of the bar. The end of the bar is flattened somewhat, and a slab is laid upon it as in Fig. 3006, the appearance after the first weld being shown in Fig. 3007. It is then turned upside down, and blooms are piled upon it as in Fig. 3008. After these are welded the end is shaped up round and to size. The extreme end is again flattened, or "broken down," as it is termed, and first a slab, and after reheating, blooms are added, as already explained; when these are welded and forged enough to consolidate the ma.s.s the ma.s.s is rounded up again, thus increasing the length of finished shaft. The end is again broken down and a slab added, and so on, the shaft thus being forged continuously from one end, and being composed of alternating slabs and blooms.

To forge this shaft 118,000 lbs. of blooms, 185 tons of coal, and 360 days of labor were required, the time occupied being 34 working days.

The slabs are simply forged pieces of larger dimensions than the blooms, and more thoroughly worked, the difference between slabs and blooms being that there is more waste with the blooms than with slabs, because the blooms heat quicker than the forged part of the crank.

Between both the slabs and the blooms there are placed rectangular pieces to hold them apart, and let the furnace heat pa.s.s between them, the arrangement of these pieces being shown in Figs. 3009 and 3010.

Figs. 3011 to 3024 (which are taken from _Mechanics_), represent the method employed to forge the crank shaft of the United States steamship Alert.

[Ill.u.s.tration: Fig. 3005.]

[Ill.u.s.tration: Fig. 3006.]

[Ill.u.s.tration: Fig. 3007.]

[Ill.u.s.tration: Fig. 3008.]

[Ill.u.s.tration: Fig. 3009.]

[Ill.u.s.tration: Fig. 3010.]

[Ill.u.s.tration: Fig. 3025.]

[Ill.u.s.tration: Fig. 3026.]

[Ill.u.s.tration: Fig. 3027.]

[Ill.u.s.tration: _VOL. II._ =FORGING UNDER THE HAMMER.= _PLATE XVII._

Fig. 3011.

Fig. 3012.

Fig. 3013.

Fig. 3014.

Fig. 3015.

Fig. 3016.

Fig. 3017.

Fig. 3018.

Fig. 3019.

Fig. 3020.

Fig. 3021.

Fig. 3022.

Fig. 3023.

Fig. 3024.]

Fig. 3011 represents the crank shaft, and Fig. 3012 an end sectional view, showing how the throws were built up. The first operation was to forge the saddles shown in Fig. 3013, these being the pieces that are shown between the cap and the wrist.

These saddles were made in halves, each half appearing as in Fig. 3014.

From a pile and weld of blooms on the porter-bar, enough to make the two halves, one half was cut off. The other half was then drawn down on the porter-bar, and the first half was then piled on the latter, as shown in Fig. 3015. The square cross bar goes clear across and projects about an inch at each side. The back pieces were short bits. The square cross bar makes the saddle less liable to split in welding it on to the square shaft. Two "caps" were also made before the forging of the shaft itself began. These are shown in Fig. 3016, and their position in the finished work is shown in Fig. 3012.

The shaft itself was piled, welded, and drawn on the porter-bar in the usual manner, until the location of a crank was reached. Then a part of the work some distance from the new end was squared, as shown in Fig.

3017, and on this square the saddle was piled to heat and weld, as shown in Fig. 3018. As will be seen, the saddle rested upon the outer lines of the angle. The first blow was struck square on the top of the saddle, and after three or four blows the job presented the appearance shown in Fig. 3019. The piece was now turned so as to lie as shown in Fig. 3020, and worked with blows on the sides to the shape shown in Fig. 3021. This opened the top of the juncture of the saddle and squared the shaft down to the point where the weld was good. The piece was then turned back to the position shown in Fig. 3019, and worked with blows which again closed the angle on top, and made the weld good all through. The piece was then returned to the furnace, and at the next heat the saddle was squared up and finished, and the cap was piled on top of the saddle, as shown in Fig. 3022. The cap was welded on at the next heat, and two cheeks, like that shown in Fig. 3023, were laid upon one flat of the crank and pinned with 1-5/8-inch round pins. One of these pins is shown in the figure. Bits of iron were put under these cheek pieces in the usual manner. As the cheeks were very much smaller in section than the crank body, it was necessary to turn them over away from the fire, or else the cheeks would be burned before the crank body was hot enough to weld. To prevent the cheeks from falling off in the furnace the pins were put in as described before heating. After two cheek pieces had been welded on one side, two more were added on the opposite side, and then the crank was finished, as shown in Fig. 3024.