Another method of upsetting with the hammer, which is called “backing up” the metal, is shown in [Fig. 37]. This method does not upset the metal so rapidly, because the force of the hammer blows jars the hand and arm which hold the bar.
Upsetting by ramming or jarring is thrusting the metal forcibly against some heavy object like the surface plate, the swage block, or the anvil. Figure [38] shows upsetting by this process. This method is very effective and is used mostly when the metal is long enough to be held with the hands, as shown.
Fig. 38.—Upsetting by Ramming.
56. Forming is a term generally applied to the making of a forging with special tools, dies, or forms. This process may include bending, punching, and other operations.
Swages are used for forming. A block of steel with a depression of a special design is known as a forming die; a number of other tools and appliances may be used for forming, but it is needless to mention them here.
57. Straightening is one of the most frequent operations. When metal is being forged, the various blows have a tendency to make it crooked, and if the work is supposed to be straight when finished, it should be so.
Fig. 39.—A, Straightening with the Hammer;
B, Straightening with the Swage.
There is as much skill required to straighten properly a piece of metal as there is to bend it. The most common method (A, [Fig. 39]) is to hold the metal lengthwise on the anvil with the bowed side or edge upwards, then to deliver the blows at the highest point of the bow. The blows will be most effective at the point where they are delivered, so they should be distributed in order to get the object perfectly straight and to avoid making unsightly hammer marks.