Chapter XXXIII: Forging (2)

Fig. 2887 represents a tongue weld, and it is obvious that to insure soundness the wedge piece should fit in the bottom of the split, which may be well closed upon it by the hammer blows.

Fig. 2888 represents an example of a [V]-weld applied to welding up a band that is to be square when finished, and as the lengths of the sides must be equal when finished, the side on which the weld is made should be made shorter, so that in stretching under the welding blows it will be brought to its proper length. The [V] form of weld is employed because it stretches less in welding than the lap weld. The [V]-piece to be welded in should bear at the bottom of the [V], and the weld made by fullering.

Welds of this kind are obviously most suitable for cases in which the weld is required to influence the shape of the piece as little as possible. The figures above, which are taken from _Mechanics_, illustrate as an example the repairing of a broken strap for the beam of a river steamboat. The crack is at A, Fig. 2889, and is held together by a clamp as shown; a [V]-recess is cut out as in Fig. 2890, and this recess is fullered larger, as in Fig. 2891. A [V]-block is then welded in. The strap is then turned over a second [V]-groove, cut out and fullered out, and a second [V]-piece welded in. By thus welding one side at a time the welding is taken in detail as it were, and the blows can be less heavy than if a larger weld were made at one heat, as would be the case if but one [V] block were used. A similar form of weld may be employed to form a square corner, as is shown in Fig. 2892, which is taken from "The Blacksmith and Wheelwright." In this example the inside corner is shown to have a fillet, which greatly increases the difficulty of the job. The weld is made by first fullering the [V]-piece on the sides and on the rounded corner and then laying the piece on the anvil to forge down, the fullering leaving the finished job as in Fig. 2893.

When one piece has to be driven on to the other, the weld is called a pump-weld, for which the ends should be rounded as in Fig. 2894, so that they will meet at their centres, and will, when struck endways to make the weld, come to the shape shown in Fig. 2895.

It is obvious that in this case the interior of the iron comes together and is welded, and that dirt, &c., is effectually excluded; hence if the iron is properly heated the weld may be as sound as a lap weld, and is preferred by many as the sounder weld of the two. When a stem requires to be welded to a large flat surface, the pump weld is the only one possible, being formed as in Fig. 2896, in which the stem is supposed to be welded to a frame. The plate is cupped as shown, and the metal being driven up on the sides as much as possible, the stem overlaps well at C B, so that it may be fullered there. The stem should first meet its seat at A, so that dirt, &c., may squeeze out as the welding proceeds.

Figs. 2897 and 2898 represent an example of welding a collar on round iron. The bar is upset so as to enlarge it at A, where the collar is to be. The collar is left open at the joint, and while it is cold it is placed on the red-hot bar and swaged until the ends are closed. The welding of the whole may then be done at one heat, swaging the outside of the collar first. Unless the bar is upset there would be a crack in the neck B of the collar on both sides.

WELDING ANGLE IRON.--Let it be required to form a piece of straight angle iron to a right angle.

The first operation is to cut out the frog, leaving the piece as shown in Fig. 2899; the width at the mouth A of the frog being 3/4 inch to every inch of breadth measured inside the flange as at B.

The edges of the frog are then scarfed and the piece bent to an acute angle; but in this operation it is necessary to keep the scarfs quite clean and not to bend them into position to weld until they are ready for the welding heat; otherwise scale will form where the scarfs overlap and the weld will not be sound.

The heat should be confined as closely as possible to the parts to be welded; otherwise the iron will scale and become reduced below its proper thickness.

The iron is then bent to the shape shown in Fig. 2900; and the angle to which it is bent is an important consideration. The object is to leave the overlapping scarf thicker than the rest of the metal, and then the stretching which accompanies the welding will bring the two arms or wings to a right angle.

It is obvious, then, that the thickness of the metal at the weld determines the angle to which the arms must be bent before welding. The thicker the iron the more acute the angle. If the angle be made too acute for the thickness of the iron at the weld there is no alternative but to swage the flange down and thin it enough to bring the arms to a right angle. Hence it is advisable to leave the scarf too thick rather than too thin, because while it is easy to cut away the extra metal, if necessary, it is not so easy to weld a piece in to give more metal. In very thin angle irons, in which the wastage in the heating is greater in proportion to the whole body of metal, the width of the frog at A in Fig. 2901 may be less, as, say, 9/16 inch for every inch of angle-iron width measured as at B in the figure. For angles other than a right angle the process is the same, allowance being made in the scarf-joint and bend before welding for the stretching that will accompany the welding operation.

The welding blows should be light and quick, while during the scarfing the scale should be cleaned off as soon as the heat leaves the fire, so that it will not drive into the metal and prevent proper welding. The outside corner should not receive any blows at its apex; and as it will stretch on the outside and compress on the inside, the forging to bring the corner up square should be done after the welding.

The welding is done on the corner of an angle block, as in Fig. 2901, in which A is the angle iron and B the angle block.

To bend an angle iron into a circle, with the flange at the extreme diameter, the block and pins shown in Fig. 2902 are employed. The block is provided with the numerous holes shown for the reception of the pins. The pins marked 1 and 2 are first inserted and the iron bent by placing it between them and placed under strain in the necessary direction. Pins 3 and 4 are then added and the iron again bent, and so on; but when the holes do not fall in the right position, the length of the pin-heads vary in length to suit various curves.

To straighten the iron it is flattened on the surface A and swaged on the edge of the flange B, the bending and straightening being performed alternately.

When the flange of the angle iron is to be inside the circle, as in Fig. 2903, a special iron made thicker on the flange A is employed. The bending is accomplished, partly by the pins as before, and partly by forging thinner, and thus stretching the flange A while reducing it to its proper thickness.

TO FORGE A BOLT BY HAND.--The blanks for bolts must be cut off sufficiently long to admit of one end being upset to form the head, the amount of this allowance, obviously, being determined by the size of the head.

Fig. 2904 is a side view, partly in section, and Fig. 2905 a top view of an anvil block for upsetting the ends of blanks to form the heads of bolts. The stem fits into the square hole of the anvil. The tongue is pivoted as shown in the top view to two lugs provided on the block; upon the tongue rests a steel pin whose length determines the height to which the blank will project above the top of the block, and, therefore, the amount or length of blank that will be upset to form the head, this amount being three times the diameter of the bolt for _black heads_.

The hole for the blank is made about 1/64 inch larger in diameter than the designated size of the bolt, to permit of the easy extraction of the blank after it is upset, this extraction being accomplished by striking the end of the tongue with the hammer. If the block is made of cast iron the upper end of the hole will become worn after forging five hundred or six hundred bolts, leaving the bolts with a rounded neck, as at C C in Fig. 2906; a steel block, however, will forge several thousand bolts without becoming enlarged.

An excellent plan is to provide the block with removable dies, such as at _d_ _d_ in Fig. 2907, which are easily renewed, a number of such dies having different diameters of bore fitted to the same block.

When the bolt end is sufficiently reset or enlarged to form the head it is laid in a bottom swage, containing three of the six sides of the hexagon, and a hammer blow on the uppermost part of the end forges a flat side. After each blow the work is revolved one-sixth of a revolution, and as the angles of the swage are true they obviously true the angles of the bolt head. After the head has been roughed down it is necessary to flatten it again under the head and on the end, for which purpose it may be placed in the heading block shown in Fig. 2904, after which the sides of the head may be finished and the cupping tool for chamfering the head applied.

The bolt may require passing from the heading tool to the swage several times, as forging it in one direction spreads it in another.

In shops where bolt-making is of frequent occurrence a special bolt-making device is usually employed. It consists of an oliver or foot hammer, having two hammers and an anvil; in the square hole at one end of the anvil fits a hardy or bottom chisel, such as shown in Fig. 2908, for cutting up the bar or rod iron into bolt blanks; A is the anvil, H the hardy, and G a gauge to determine the length cut off the rod R to form a blank. An upsetting or heading device corresponding to that in Fig. 2907 is provided, and at the other end of the anvil is the swage for forming the bolt head.

The object of having two hammers is that one may be used for the upsetting of the blank and the other for the swage. The swaging hammer is provided with a hole and set-screw to receive top swages, and bolt hammers are adjustable for height so that they may be set so that their faces will meet the work fair.

Figs. 2909 to 2911 represent front, side, and top views of Pratt & Whitney's portable bolt-forging device. It is provided with an elevating screw that permits the employment of a single bolster-pin for all lengths of bolt for a given diameter, instead of requiring a separate pin for each different length of bolt. In the figures, A is a frame carried upon wheels, and to which is pivoted at C C the jaw D. The bolt-gripping dies are shown at E F. A treadle G is pivoted at H, and acts upon the lower end of D, causing the die F to grip or release the bolts, as may be required. The bolster-pin rests upon the end of the screw I, which enters at its foot a split nut J, which is caused to grip and lock the screw by operating the nut of the bolt K that passes through the split of the nut. L is a spring that lifts the treadle when it is relieved of the pressure of the operator's foot.

At M is a leather washer to protect the nut J from the scale that falls from the forging. The operation is as follows:--

The nut K is released and the screw I operated to suit the length of bolt required. Then J is caused to clamp the screw by operating the nut K. The blank for the bolt is placed in the dies resting on the bolster-pin, which in turn rests upon the end of the screw I. The treadle G is depressed, and the bolt blank clamped between E and F. The helper then with the sledge upsets the blank end to form the bolt head, and the blacksmith forges it to shape in the former bar B, which is provided with impressions for the form of head required, these impressions being of varying sizes, as shown. The device is so strongly proportioned as to be very solid, and is found to be a most useful addition to the blacksmith's shop.

Fig. 2917.

Fig. 2918.

Fig. 2919.

Fig. 2920.

Fig. 2921.

Fig. 2922.

Fig. 2923.

Fig. 2924.

Fig. 2925.

Fig. 2926.]

To forge a turn buckle, such as in Fig. 2912, we bend two rings, such as in Fig. 2913, and weld into the open ends a piece as shown in Fig. 2914, on the opposite side a recess A, Fig. 2915, is cut out to receive a second piece, which being welded in the work appears as in Fig. 2916, and the end may be drawn taper. Two such pieces welded together obviously complete the job.

Fig. 2917 represents a yoke for the slide valve of a steam engine or a locomotive, which may be forged by either of the following methods:

Fig. 2918 represents a stem A welded into the bar B, which may be bent to the required rectangle and welded at the ends.

A second method is to jump the stem D and split it open as in the side view in Fig. 2919. The bar E is forged with a projecting piece to go in the split of D, and after the weld is made, bar E is drawn to size as shown, leaving the two projections _x_ where the corners are to come, which is necessary in order to have sufficient stock to bring the corners up square. The ends of E are split open as in the end view at F, and a piece G is then welded to F.

In a third method the end of the stem is rounded for the weld, as shown in Fig. 2920. The ends of the bar J are then split open and piece K welded on.

It is to be observed with reference to the two last methods that in hammering to forge the weld the frame is closed, so that after welding the swaging to finish may be carried on until the frame is brought to square, and any superfluous metal may be cut away; whereas if the kind of weld is such as to stretch the sides, it may happen that to get a sound weld will stretch the side welded too long and throw the frame out of shape.

Suppose, for example, that a scarf weld were made on the side of the yoke opposite to the stem, and if, in welding, the scarf is hammered too much, it would draw it out too much and throw the whole frame out of shape, as in Fig. 2921, so that the welded side would require to be jumped to bring it back to the proper length again.

A fourth method is to take a piece of iron and punch a hole in it, and then split it open up to the hole, as in Fig. 2922, and by opening out the split form the stem and part of the frame out of the solid, forging the remainder of the frame by the plan described for either the second or third methods.

A fifth method is to make the weld of the stem as in Fig. 2923, then forge out the bar B, leaving projections _x_ _x_ to bring the corners _y_ _y_ up square, and after bending to shape and squaring up to weld in a piece C.

A sixth method is to form the band first as in Fig. 2924, form the stem as in Fig. 2925, and weld as in Fig. 2926.

Figs. 2927, 2928, and 2929 represent a method of forging a fifth wheel for a vehicle. A rectangular piece of Norway iron is fullered to form the recess at C in Fig. 2927. Holes are then punched at _h_ and splits are made to the dotted lines shown in the figure. The ends are then opened out, forming a piece such as in Fig. 2928. The letter A represents the same face of the work in all the figures, being the edge in Fig. 2927, and the top face after the ends are opened out. The four arms may then be dressed to shape, the two lower ones being drawn out and threaded before being finally closed to shape. A piece may then be welded on one end, as at B, to complete the circle.

To forge a double eye, such as in Fig. 2930, we may take a piece of sufficient size and fuller at _a_ _a_, Fig. 2931; a hole is then punched at _b_, and it is then split through to the dotted line in Fig. 2931, and opened out as in Fig. 2932, and then forged to shape.

BENDING.--Fig. 2933 represents a tool for bending pieces of small diameter to a short curve, either when cold or heated. In bending hot iron it is advantageous to confine the heat as closely as possible to the part to be bent, as a more true bend may then be obtained.

As an example in bending, let it be required to bend a straight shaft into a crank shaft, and the following method (from "The Blacksmith and Wheelwright") is pursued. The shaft is first bent as in Fig. 2934. The piece is next bent as in Fig. 2935, and finally as in Fig. 2936, the corners A A and B B corresponding in all the figures.

BLACKSMITH'S BENDING BLOCKS.--In cases where a great number of pieces of the same size and shape are required to be bent during the forging process, a great deal of time may be saved and greater accuracy secured in the work by the employment of bending devices. Thus, in Fig. 2937 is shown at A a clip requiring to be bent to the shape at B. A pair of tongs is provided with a hole at C to receive the stem of the clip, and the jaw D is made of the necessary width to close the ends of the forging upon. It is obvious that the hole C being in the middle of the width of the tong jaw, the wings will be equidistant from the pin.

Figs. from 2938 to 2943 represent bending devices.

Figs. 2938, 2939, and 2940, represent a "former" for a stake pocket for freight cars. A is a cast-iron plate having a projection B, around which the stake pocket C is bent. D is fast upon A, and affords a pivoted joint for the bending levers E F. The work is placed in the former as shown in Fig. 2939, and levers E F are swung around to the position shown in Fig. 2938. To enable the work to be put in and taken out rapidly and yet keep it firmly against the end of B, a hand-piece G is used as in Fig. 2940, its form being more clearly shown in the enlarged Fig. 2941. Sufficient room is allowed between B and D to admit the work, and the end of the piece G, which is pressed in the direction denoted by the arrow in Fig. 2940, forcing the work against B. A number of the pieces are piled on the fire so as to heat them sufficiently fast to keep the former at work, and the bottom piece is the one taken out.

The corners of the work are by this process brought up square and the faces are kept out of wind. The surface A forms a level bed. These advantages will be readily appreciated by all smiths who have had comparatively thin work to bend to a right angle in the ordinary way.

Figs. 2942 and 2943 represent a similar former for the step irons of freight cars. In Fig. 2942 the piece is thrown in place ready to be bent, its ends being fair with the lines J K on the bending levers E F. In Fig. 2943 the levers are shown closed and the work C therefore bent to shape. The bed plates A are mounted on a suitable frame to raise them to a convenient height for the blacksmith.

FORGING A STABLE-FORK.--In the manufactories where stable and hay forks are made, the whole process of forging is done under the trip hammer, and is conducted as follows:--

To forge a four-tined fork, such as in Fig. 2944, a blank piece of steel is employed, its dimensions being 5-3/4 inches long, 7-3/4 inches wide, and 1/2 inch thick. The first operation is to swage down one end, as at A in Fig. 2945. A split is then cut down as at B in Fig. 2946. The split is then opened out as in Fig. 2947, and is fullered and drawn out at C. Two more splits are then made at D D, and the ends are bent open as in Fig. 2948, when the four tines E E and F F are drawn out and shaped out. The stem, A, Fig. 2945, is then finished for the handle.

The following example of forging under the hammer is derived from _The Engineer_, of London, England. Fig. 2950 shows the piece to be forged. A block of iron, Fig. 2951, is drawn out as in the figure, the dimensions of A and B being considerably above the finished ones. A forked tool T, Fig. 2952, may be used to nick the two grooves shown in Fig. 2953, which marks the locations for the hub and forms a starting guide for the two fullering tools shown in Fig. 2954, one of which is held by the blacksmith and the other by the helper. After this fullering the forging will appear as in Fig. 2955. The ends E, F may then be drawn out, having the shape as in Fig. 2956. To shape the curve between the side of the hub and the body of the stem, grooves are formed as in Figs. 2957 and 2958, Y and B being top and bottom half-round fullers, and these two grooves are subsequently made into one by means of larger half-round fullers, as in Fig. 2959. The object of making two small fullered grooves and then making them into one is to prevent the fullering from spreading the body of the stem by lessening the strain due to using a large fuller at once. The piece now appears as in Fig. 2960.

The next operation is to cut or punch away the metal between the ends of the hub and the body of the piece, which is accomplished as follows:

A top and bottom die and block are made to contain the work, as in Fig. 2961, A and B being the work ends. Through these dies are two holes for two punches which are driven through together as marked; the dies are held fair, one with the other, by four holes in the lower and four pins in the upper one, a section and top view of the dies being shown in Fig. 2962.

The piece is at this stage roughed out to shape all over, and may be finished between the pair of finishing dies shown in Fig. 2963, which also represents a plan and sectional view, _a_, _b_, _c_, _d_ being the holes to receive guide pins in the upper die.

An excellent example of forgings in Siemens Martin steel is given in the following figures, being the rope sockets for the Brooklyn Bridge.

Fig. 2964 represents two views of the forgings, and it will be readily perceived that they are very difficult to make on account of the taper hole, which is shown in dotted lines. The first operation was to take a bar of steel 6-1/2 inches square and punch a hole, as at A Fig. 2965.

Next the piece was fullered at B, C by the fuller A, Fig. 2966, and cut partly off as at D. The fullering at B was then extended by a spreading fuller, shaped as at B, and the end E was drawn out. Then the piece was cut off at D. Next the spreading fuller was applied to C, and the forging appeared as in Fig. 2967. The end F was then drawn out, and the appearance was as in Fig. 2968.

The next operation was to enlarge the hole A, Fig. 2965, by drawing taper mandrels through it, the mandrels being about 7 in. long, having 1/2-in. tapes on them, and being successively larger. With the last of these mandrels in the hole the hub was drawn out to length and diameter, leaving the forging roughly shaped, but having the form shown in Fig. 2969.

To finish the hole the forging was then placed in a block such as shown at G, in Fig. 2970, a finishing punch being shown at H in the figure.

The next operation was to let the steam hammer down upon the face of the punch and bring up the wings E F parallel, but not more than parallel, as then the mandrel could not be got out; the forging then appearing as in Fig. 2971.

The next process was to put in a bar mandrel such as shown in Fig. 2972 at I, the pieces J, K fitting on their sides to the mandrel and being curved outside to the circular and taper shape of the hole. The wings E F may then be closed on the mandrel to their proper width and the whole hub end being trimmed by hand, all the previous work having been done under the steam hammer. The hub being finished the key M may be taken out and the washer L taken off, when I can be pulled out, leaving J K to be taken out separately. A pair of tongs are then put through the finished hub end, while the wings are punched and trimmed under the steam hammer, and subsequently finished by hand.

The forging of wrought-iron wheels for locomotives is an excellent example. The spokes are first forged in two pieces, as 1 and 2 in Fig. 2973, and then welded to form the complete spoke. Piece 1 is first forged in dies under the steam hammer to the form shown in Fig. 2974, the dimensions being correct when the faces of the dies meet. The stud C D is then drawn out to the required length and dimensions.

The upper half of the spoke is first blocked out under dies to the shape shown in Fig. 2975, and the block B spread so as to form a section of the wheel rim, as shown in Fig. 2976, in which D is a die, L a movable piece wedged up by the wedges W W, and removable to enable the extraction of the forging, and F is an end view of the fuller, the use of which is necessary to cause the metal to spread sufficiently in the direction of the dotted lines. The corners of the rim are then cut off, as shown in Fig. 2973, and the rim is bent in a block having its top face of the necessary curve, as in Fig. 2977, A being the block, and B a piece movable, to allow the extraction of the work, and fastened in place by the key or keys C. The two pieces are then welded together, their lengths, &c., being gauged by a sheet-iron template, formed as in Fig. 2978. The welding is usually performed with sledge-hammers, but as soon as the pieces will hold well together, the drawing down is done under a steam hammer.

The spokes thus forged are then put together, as in Fig. 2979, B representing a wrought-iron band, encircling the rim of the wheel and closed upon the same by the bolt and nut at N.

Two washers are then forged, to be placed and welded in as at W W, in Fig. 2980.

The welding together of the spokes and of the washers to the spokes proceeds simultaneously. The washers are heated to come to a welding heat at the same time as the wheel hub is at a welding heat, and the two are welded together under a steam hammer. During the heating of the wheel hub, however, the band B, Fig. 2979, is tightened up with the screw to bring the spokes into closer contact when heated to the welding point.

The seams between the spokes at the circumference of the hub are welded with bars as shown in Fig. 2981, in which R R are two bars of iron which are operated by hand as rams. The wedge shape of the washers on their inside faces performs important duty in spreading the metal as well as simply compressing it, giving a much more sound weld than a flat washer or plain dish would.

The rim of the wheel is welded up as follows:

In Fig. 2982 are shown four spokes of the rim as they appear after the hub is welded. Into the [V] spaces, as _a_, _b_, _c_, _d_; wedges of metal, of the form shown at E, are welded, after which the surplus metal of E is cut away, and the rim is solid as at F. In this process, however, it is necessary to weld all the pieces on one side of the wheel, as at _a_ _b_, &c., except one, which must be left unwelded until all the pieces save one on the other side are welded, and the wheel must be allowed to become quite cool before these last two pieces are welded. Otherwise the strain induced by the contraction of the wheel rim while cooling will often cause the rim to break with a report as loud as that of a rifle. In those cases in which this breakage does not occur the wheel will be very apt to break at some part of the rim, when subjected to heavy shocks or jars.

The Figs. 2983 to 2999 (which are taken from _Mechanics_), illustrate the method employed to forge the rudder frame of the steamship _Pilgrim_.

A side elevation of the rudder frame is shown in Fig. 2983.

The forging is made in eight separate pieces, which are so united as to make three pieces. These three pieces are finally joined by five welds. The whole length being 29 feet 11-3/4 inches, and the weight 6,500 pounds.

The work is commenced by piling and welding on the porter-bar at the point in the shaft marked A. The stubs B and C having been previously prepared, the pile on the porter-bar is heated and welded up and drawn, shown in Fig. 2984, and scarfed as shown in Fig. 2985; the piece, shown in Fig. 2986, is then laid in the scarf and welded; then the part from B to A is finished to size, the finished forging of the post being shown in Fig. 2984. The surplus stock to the right of B, Fig. 2984, is worked down into the post E, and the distance from B to F is thus made correct without loss of stock or time. The curve at D, Fig. 2983, was worked down somewhere near, and then another pile and weld carries the job to G. Here the same operations as at first are repeated, and the arm C is welded in. There is left a good lump of stock in front of C, and by another pile and weld enough is added to make the job to I, as shown in Fig. 2987. Holes are then punched at J and L, and the piece of stock M cut entirely out. A cut is made to L with a hack opening out the piece N from the shaft. A taper punch, with a 3-inch point and a 4-inch head, is then driven at L; to throw the piece N out into the position shown at N^{1}, Fig. 2983; N^{1} is then finished, and the post from L to J brought to forging size; then, by the ordinary process of piling, welding and drawing, the shaft is finished from I to O. Next the porter-bar is cut off, so as to leave stock enough to make the lower part of the shaft, as shown in Fig. 2988. A hole was punched at Q, and the stubs drawn out, as shown in Fig. 2989, which gives the post complete.

The pieces S and T, and the tiller V, having been forged, as shown in Fig. 2991, the upper member of the frame is started on the porter-bar at W, Fig. 2983, and filed, welded and drawn to make the job as far as X^{1}. Wooden templates, such as in Fig. 2992, are provided for the pieces of the frame, the first extending from W to X^{1} and X, and the second including the part from X^{1} to X^{2} and X^{3}. After W, X^{1} has been drawn out with lumps left where the tiller and the arm S are to be joined, the scarf is made for the tiller and that is welded in, and the job finished to piece S. The scarf for S is then made, and S welded in. This makes the upper member of the frame. The lower member is made in the same way, starting at X^{3}. These two members are shown complete in Fig. 2993. The post, Fig. 2989, was sent to the machine shop, and was turned, planed, bored, and slotted, as shown in Fig. 2990. The frame was now ready to be pieced up, by welds at W, X, X^{1}, X^{2}, and X^{3}, Fig. 2983.

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 illustrated 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 scrap iron, which is piled as in Fig. 3000. For the forging in question this scrap iron consisted of old horseshoes, boiler-plate clippings, boiler rivets and old bolts, and the first step in the manufacture is to form this scrap into piles ready for the furnace.

These piles are made upon pieces of pine board 1/2 inch thick by 16 inches long by 10 inches wide. On these the scrap is piled about 14 inches high, each pile weighing about 270 pounds. After piling, the scrap 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 scrap 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 scrap 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 scrap had united by melting rather than by any welding process.

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 mass, forms practically a base wherefrom to build up the shaft. The construction of the furnace is shown in Fig. 3004, the heat, after passing 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 mass the mass 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 pass 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.

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.

As will be seen by inspection of Fig. 3012, the weld between the cap and the saddle comes about the middle of the wrist, and the cheek pieces support the cap sideways. By means of the piles and welds described, the grain of the iron was so disposed as to offer the most resistance to working strains. This method was devised by Mr. Farrell Dorrity, of the Morgan Iron Works.

FORGING LARGE CRANK SHAFTS.[45]--The following paper describes the method of forging marine crank shafts adopted at the Lancefield Forge, Glasgow. It will be better understood if a short account is first given of the ordinary methods in use for the same purpose.

[45] From a paper read at the Glasgow meeting of the Institution of
Mechanical Engineers, by W. L. E. MacLean.

"_First Method._--The most common method is technically termed by the forgeman, 'finishing the piece before him.' He begins with a staff or stave, as shown in Fig. 3025, suspended by a chain from the crane, and made round for the convenience of manipulating under the steam hammer; this stave is used over and over again for many forgings, as it is merely the "porter" to carry the piece and enable it to be worked. The forging is begun by two or three slabs being placed on the stave as at S S S, and then inserted in the furnace. These slabs are flat blocks made up of pieces of scrap iron, which have been piled and heated, and then welded together. After being brought to a welding heat in the furnace, the slabs are withdrawn, placed under the steam hammer, and beaten down solid. The piece is then turned upside down, and two or three similar slabs placed on the opposite side, as shown at S S. When sufficient iron has been thus added to form the collar of the shaft (assuming it is to have a collar), it is rounded under the hammer, as at C, Fig. 3026, and the body of the shaft next to the collar is roughly formed, as at D. More slabs, S S S, are added to bring out the body, and afterwards the crank itself is proceeded with, on the same plan. The piece will begin to assume the appearance of A, Fig. 3026. Then more slabs are welded on the top, as at S S S, till the depth of the crank is obtained, after which the forgeman proceeds to finish the collar and body of the shaft, as shown. The collar on being finished is cut all round, as shown at C D, Fig. 3027, so that it may be more easily detached from the stave when the shaft is completed, leaving only sufficient connection to carry it till then. The forgeman then cuts the gable of the crank as at E G, and rounds up the body and neck as at B N, Fig. 3027.

"This, it will be observed, is a speedy process, and would invariably be adopted if it were not attended with a very serious drawback; it is very hazardous to the solidity of the forging. For it will be easily understood that not above a third of the crank itself can be thus formed, because the iron at the neck N would not carry a greater mass; if the whole mass of the crank, or even the half of it, was formed before the body and neck of the shaft were finished, a proper heat could not be taken on the body and neck for finishing, without the neck giving way or rupturing. Indeed, as it is, the undue proportion often causes the shaft to be strained at this part, where most strength should be, so that it is rendered weak, and a flaw is developed which by-and-by causes it to be removed from the steamer as dangerous and useless, if indeed it does not break outright; so that the forgeman, if he adopts this method, must be very careful to proportion the amount of iron he has massed in the furnace to the size of the body he is finishing, otherwise the weakening above mentioned will take place. All marine engineers will easily recognise this defect, which frequently occurs, but the cause of which is probably not well understood. Such a flaw will present a similar appearance to that shown at F, Fig. 3033, taken from an actual example.

"This difficulty of proportioning the part of the crank first forged to the size of the neck, will be still better understood by the appearance of it in the furnace, as shown in Fig. 3028. Having reached this stage, with one end of the shaft completed, as also that portion of the crank itself which of necessity was completed before the collar was cut, in order that the neck might be finished, no more iron can be added on the top edge, as it is up to the full depth already; it must therefore be added on the flat, as in Fig. 3029, where the piece is shown on its flat side in the furnace, the finished portion being outside the furnace door. A number of slabs S S S are then placed side by side to bring out the width of the crank further; these being welded down, the piece is turned upside down, and the process repeated on the other side. Afterwards other slabs are similarly placed on both sides, as shown in Fig. 3030, of which one is the flat, and the other is the edge view of the crank at this stage; and this is continued until sufficient iron has been massed to allow of the other gable of the crank being cut down, as at A, Fig. 3031, and sufficient also to allow of the other part of the body B being rounded and prepared for further piecing out.

"Now it will be observed that the first gable finished has the slabs all welded on the edge of the crank, and the hammering has all been on the edge; hence the subsequent hammering on the flat has a tendency to open up the weldings, if they have not been thoroughly made. A section taken at A B, Figs. 3028 and 3029, will show as in Fig. 3032, on the left, the weldings being across the web of the crank; the circle indicates the section which the crank pin would present if cut through there. But when the slabs are placed on the flat afterwards, some of the joinings of the ends of the slabs, or "scarf ends," are certain to fall within the crank pin, as seen in Figs. 3028 and 3029; therefore the section through C D, Fig. 3030, will show somewhat like Fig. 3032 on the right, and the crank pin necessarily includes some of these flaws. The flaw thus produced, called 'a scarf end in the pin,' is readily recognizable by all marine engineers; at F, Fig. 3033, is a sketch from an actual occurrence.

"When the second gable is cut, and the other end is rounded, there is only the other collar to be put on (if a double-collared shaft), and the forging is completed.

This method is so speedy, compared with any other, that it is often resorted to even at the risk of making a bad forging; and too many broken shafts testify to the fact. Besides, it may be observed that in making a double crank shaft, while the one crank may be made in this way, the other must; for, the first crank, A, Fig. 3033, being completed, and the body, B, between the two cranks, also completed, the second crank, C, must of necessity be pieced off this body, even at the risk of the neck N being strained. This may account for the many instances in which one of the cranks of a double crank shaft gives way, rendering the shaft useless; and also for the plan, now almost universal, of making the two cranks separately and coupling them together; a further object being, no doubt, to have the means of replacing a defective half, if need be, without losing the whole shaft.

"At Lancefield, when a double crank shaft is to be made, the after crank, A, is first made by the method afterwards described, so as to insure that this crank, through which, as being next the propeller, all the power of the engine passes, is perfectly sound; and in piecing the other crank off the body, it is worked with slabs on the flat instead of on the edge, as afterwards described.

"The writer's own opinion is that the crank is the most important part of the shaft, and, therefore, at all costs, should be made first. Others, no doubt, may take the same view, and, to avoid the risks just mentioned, may adopt the process described in the second method.