Tie a rope to each end. First wrap one rope clockwise around the rod of the drill bit, tightening it, with the end of the rope fixed to the rod.
The other rope is wrapped counterclockwise around the rod, relatively loose, with its end also fixed. There is a height difference between this rope and the one above.
The bow drill is complete.
Let's test it first.
Randomly picked a block of wood.
Press the drill bit down, holding the back end of the drill bit with the left hand.
Use the right hand to draw the bow back and forth as if sawing, causing the line to rotate the drill bit.
The drill bit is mounted inside a round wooden stick, with significant friction between the stick and the line.
The junction between the round wooden stick and the back end of the drill bit is square, not circular, preventing relative rotation.
The round wooden stick and the wooden block at the back have a pivot and bearing relationship.
