Water-Driven Machine for Drawing Metal Wire
Endless screws and gearing, turned by water, pull a four-sided bar through a die
Leonardo describes and draws a machine for 'trafilazione' — drawing metal out into long wire or bars by pulling it through a die. He argues that it must be driven by water rather than by hand, since the endless screws (viti sanza fine) that power it work with immense but very slow force. The large figure shows two big toothed wheels and an inclined toothed shaft rising from a horizontal star-wheel at the base, with smaller detail studies of the interlocking die-pieces and a lettered draw-plate at the right.
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Water must drive the wire-drawing machine, not the human hand
The instrument must be moved by water: were it driven by a man's hand it would be so slow that the work would yield little fruit. Water perfects the immense power of the endless screws that engage in this motion. If the four-sided piece is to have a uniformly concave side, the wheel b is removed and the wheel a is used instead.
The four sides of the bar are drawn at different moments
Because the jaws (labri) of the draw-plate are not all the same distance from the motor, the beginning of the drawing must be staggered: of the four sides, the three lower ones are drawn before the fourth, upper side. This leaves a ridge along the upper edges that is useful at the end, when the drawn strips are joined and hammered together.
Slow, powerful descent of member b against fixed n
In the lower figure b is movable downward and n is fixed in every direction. The upper member b of the draw-plate bn descends against its lower part n with a slow and most powerful motion; the sum of that travel is measured against a knife-back when the drawn iron runs to twenty braccia in length.
Interlocking die-pieces lettered a, b, c, d
A detail shows two interlocking pieces of the die carrying the letters b, a and d, c, with a neighbouring figure lettered o, m, b, a, q, p and c, n. These small studies work out how the segments of the draw-plate fit together.