24. The punches (A, B, and C, [Fig. 11]) are merely samples of the multitude of such tools that may be required. They may be of various sizes, depending upon the requirements of the work, and either round, square, or oval in shape at the end. The hand punch A is held with one hand while blows are delivered with the other. It is convenient for punching holes in light pieces; but when the work is heavy the intense heat from the metal makes it impossible to hold a punch of this kind.
Fig. 11.—The Punches.
In such cases the handle punches B and C are employed. They eliminate the danger of burning the hand, but it is necessary to have some one act as helper and do the striking. The proper way to use a punch on hot metal is to drive it partly through, or until an impression can be seen on the opposite side after the punch has been removed; then the punch is placed on the impression and driven through the metal while it is held over the pritchel hole, the hardy hole, or anything that will allow the punch to project through without causing the end to be battered. If heavy pieces of metal are to be punched, it is a great advantage to withdraw the tool, drop a small piece of coal into the hole, and cool the punch before again inserting it. The coal prevents the tool from sticking fast, and the operation can be repeated as often as necessary.
Punches need not be tempered, because the strength of the steel from which they should be made will withstand the force of the blows, and also because the metal is generally hot when the punches are used; therefore the temper would be quickly drawn out of them. If sheet metal or light material is to be punched cold, it is advisable to harden the punch slightly; then the hole may be punched through from one side, while the metal is held on something containing a hole slightly larger than the punch. This method has the effect of producing a smoothly cut hole, provided the metal is properly placed.
Fig. 12.—The Top and Bottom Swages.
25. The top and bottom swages ([Fig. 12]) are made with semicircular grooves of different sizes to fit the various diameters of round material. The former has an eye for the insertion of a handle by which it is held when in use. The eye should be crosswise to the groove in the face. The bottom swage is made with a square projecting shank to fit loosely into the hardy hole of the anvil. It should be placed in position for use with the groove crosswise to the length of the anvil, unless the form of the forging should require otherwise. Swages are conveniently used for smoothing round material after it has been welded, or for swaging parts of a forging after they have been roughly hammered out. By dipping the top swage in water occasionally while in use, the work can be made much smoother and the scale of oxide removed; this is called water swaging.
Fig. 13.—The Top and Bottom Fullers.