A pointed instrument set on a grinding wheel
Instructions for grinding the points, beside a large machine drawing
A large, carefully drawn machine fills the sheet: a tall vertical shaft carrying a flywheel and belt drive mounted on a heavily bolted frame, with smaller detail views below. The notes tell how to lay the pointed instrument face-down with its points forward so they all rest on the wheel at a single level, having first been opened by half the back of a knife, and to grind the 'windows' first and then the opposite side. A detail is marked 'thick' and 'thin,' with the remark that this will be best.
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Setting and grinding the pointed instrument
Lay the instrument face-down and set it up with the points forward, so that all the points rest on the wheel, which is then low, keeping them at a single level; it must first be opened by half the back of a knife. Grind the 'windows' first and then the opposite part.
Machine detail marked 'thick' and 'thin'
A detail of the mechanism is annotated 'thick' and 'thin,' distinguishing two parts of the piece. Leonardo adds that it will be best done this way.