Augers for boring beams and spiral stairs around a tower
Self-clearing auger bit, a large boring screw, and ten snail-staircases
The page centres on a large screw-auger mounted in a tripod frame for boring a wooden beam. Leonardo advises boring a beam held upright, from below upward, so the hole empties itself, with a canopy to keep sawdust off the turner and a routine of first a thin auger then a thicker one; smaller auger bits and a self-clearing grooved iron are drawn at the sides. A framed inset at upper left shows a cylindrical tower wrapped by ten external spiral (snail) staircases.
On this page
Boring a beam upright with a large screw-auger
To bore a beam, hold it upright and bore from below upward so the hole empties itself. A canopy keeps the sawdust from falling on the man turning the screw, and the turners climb together with the screw; make the hole first with a thin auger, then a thicker one.
Self-clearing grooved auger bit
The iron of the auger is made with grooves so that it clears (empties) itself as it bores. A pair of augers is drawn alongside.
Ten spiral staircases around a tower
A framed inset shows ten spiral (snail) staircases wound around the outside of a cylindrical tower.