Toothed shears for cutting iron, with chains and gears
The large fragment is packed with mechanical parts; the smaller was blank until restoration.
The large mounted fragment (23a) is crowded with pen studies of mechanical components — link-and-roller chains, toothed segments, screws and a saw-like toothed rod — together with shears (forbici) for gripping and cutting iron. Two captioned diagrams explain their construction: one shows how the pivot 'a b' must be seated in the toothed shears so that it does not project from its case; the other, lettered d c b a / h g f e, sizes the jaws so the shear can take iron rods of different thickness. The smaller fragment (23b) bears only faint marks and is recorded as blank, 'invisible before restoration.' Further untranscribed notes in Leonardo's mirror hand are visible on the large fragment.
On this page
Seating the pivot in the toothed shears
A detail at the upper left shows toothed shears. The note explains that the pole or pivot 'a b' must be positioned so that it does not project beyond its case.
Sizing the shear jaws to the iron
A diagram lettered d c b a and h g f e sizes the jaws: the widest shear, which grips 'd', should accept any thick iron rod, while thinner iron ('e' or 'b') is cut in the narrower shears 'g' or 'f'.
Chains, gearing and screws
Across the top band and the lower half are repeated studies of link-and-roller chains, toothed wheel segments and screws — the components of a mechanical drive.