Machine for threading screws

"This is the way to make a screw"

The device can thread a screw positioned in the central shaft with different pitches. The blade that threads the screw is positioned on a mobile trolley connected to two lateral guide screws.
The trolley can move faster or more slowly according to the necessities of the operator who can choose among spur-wheels with different dimensions. Leonardo describes the functioning of the mechanism by indicating the different elements of the machine with different letters.
The drawing only occupies the lower part of the sheet, while in the upper part we can see oak trees, a bell, a spouting vase and two composite shafts.
Manuscript B, sheet 70