Modern Machine-Shop Practice Part 196

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.

[Ill.u.s.tration: Fig. 2934.]

[Ill.u.s.tration: Fig. 2935.]

[Ill.u.s.tration: Fig. 2936.]

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.

[Ill.u.s.tration: Fig. 2937.]

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.

[Ill.u.s.tration: Fig. 2938.]

[Ill.u.s.tration: Fig. 2939.]

[Ill.u.s.tration: Fig. 2940.]

[Ill.u.s.tration: Fig. 2941.]

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.

[Ill.u.s.tration: Fig. 2942.]

[Ill.u.s.tration: Fig. 2943.]

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:--

[Ill.u.s.tration: Fig. 2944.]

[Ill.u.s.tration: Fig. 2945.]

[Ill.u.s.tration: Fig. 2946.]

[Ill.u.s.tration: Fig. 2947.]

[Ill.u.s.tration: Fig. 2948.]

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.

[Ill.u.s.tration: Fig. 2949.]

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.

[Ill.u.s.tration: Fig. 2950.]

[Ill.u.s.tration: Fig. 2951.]

[Ill.u.s.tration: Fig. 2952.]

[Ill.u.s.tration: Fig. 2953.]

[Ill.u.s.tration: Fig. 2954.]

[Ill.u.s.tration: Fig. 2955.]

[Ill.u.s.tration: Fig. 2956.]

[Ill.u.s.tration: Fig. 2957.]

[Ill.u.s.tration: Fig. 2958.]

[Ill.u.s.tration: Fig. 2959.]

[Ill.u.s.tration: 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:

[Ill.u.s.tration: Fig. 2961.]

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.

[Ill.u.s.tration: Fig. 2962.]

[Ill.u.s.tration: Fig. 2963.]

[Ill.u.s.tration: Fig. 2964.]

[Ill.u.s.tration: Fig. 2965.]