Piano-plates
The importance of that portion of a piano called the iron frame or "plate" possessing in the highest degree all the qualities requisite for a perfect casting may be better understood when it is known that in pianos of the largest size the sum of the tension of the strings, when stretched in attuning, reaches 33 tons. It is therefore natural to suppose that skill of the highest order is brought to bear on their production. The minor manufacturers usually contract with some foundry for their supply of plates, but in most cases the restrictions as to weight and finish are so severe that even ordinary profits are never looked for by the founder. Leading firms have them made in their own foundries, where special mixtures of iron, which have been previously determined and tested, are melted down at once, and poured into as many as seventy moulds simultaneously, in order that all may be alike. The chief feature in moulding these castings is the ramming. See RAMMING.