[Fig. 2855], for example, represents a top and bottom swage for rounding up iron. For general work the recesses or seats of such swages would be made considerably oval, as in [Fig. 2856], the work being revolved slightly after each blow. This capacitates one swage for different sizes of iron. When, however, a swage is to be used for one particular size only, its cavity may be made more nearly a true half circle and may envelop one half the diameter of the work, so that when the top and bottom swages meet, the work will be known to be of the required diameter without measuring it. If the seat were made a true half circle it would lock upon the work, preventing the smith from revolving it and making it difficult to remove the swage.
Fig. 2857.
If the conditions are such that a swage must be used to perform forging rather than finishing, its seat should be V-shaped and not curved. Suppose, for example, that a piece of iron, say, 6 inches in diameter, required a short section to be forged down to a diameter of 3 inches, then the swages should be formed as in [Fig. 2857], because otherwise the effects of the blow will act to a certain extent to force the iron out sideways, for reasons which will be explained presently.
Fig. 2858.
