(1) Upsetting in large forge work may be done by holding the heated billet between the hammer and the anvil dies and bumping it with a battering ram known as a "tup" or "monkey." This is a heavy mass of iron with a smooth end and a long horizontal handle. It is suspended from the roof, and is swung like a pendulum so that it strikes the billet on end.

(2) Metal should be forged only at a red heat, though light blows for surface finishing may safely be given at a blue heat. Forging nearly cold iron is not advantageous and iron so forged should be annealed.

Fig. 150.

(3) The energy in a small hammer forced at high speed against a forging may be made the same as that in a large hammer forced at a lower speed, but the effect of the blow on the forging is not the same. A quickly delivered blow is superficial in its effect, while a slowly delivered blow from a heavy hammer is more like the squeeze of the hydraulic press, and is deeper felt. The particles of metal have time to re-arrange themselves under the slower speed of the heavy hammer.

(4) The effects of cold or hot forging, and of light or heavy hammers as mentioned in items (2) and (3) are often shown in finished forgings, sometimes to the extent of damaged parts. For example, the piece A, Fig. 150, shows how the edge of a forging looks which is forged at a good working heat and the hammer blows are felt entirely through the piece. B shows that the forging was not hot enough, or the hammer was too light, or both.