A cord drill consists of a shaft, a fly wheel and a piece of cord. The fly wheel is fitted onto the shaft so it sits about a third of the way from the bottom of the stick. The middle of the cord is then fixed to the top of the shaft. To use it the two ends of the cord are wrapped around the shaft, one end of the cord is held in one hand and the other end in the other hand. The ends of the cord are then pulled outwards. As a result the shaft and fly wheel spin with the bottom of the shaft drilling into whatever needs to be drilled. As the cords are pulled out as far as they can go, the flywheel keeps the drill spinning wrapping the cord back around the shaft in the other direction. When it stops spinning, the cords are pulled outwards again sending the drill spinning in the other direction.
I used this tool to make fire in the same way I used fire sticks. I then made fly wheels from clay and fired them. Another cord drill was made with the clay fly wheel and was fitted with a stone tip. This was then used as a drill and a hole was then drilled in a piece of wood. This piece of wood was slipped over the spindle of the original cord drill upgrading it to a pump drill.
The pump drill is basically the same tool as the cord drill with a cross bar. A hole is drilled into the cross bar and the bar slid onto the shaft. The ends of the cord are then fixed to the ends of the cross bar. To use it the cord is twisted around the spindle as before and the cross bar is pumped up and down. This causes the same motion of the drill as before.
As far as fire making goes I’ll stick to fire sticks as the parts are easier to make. But for people with soft hands, this would be a good method for making fire without getting blisters. The effort during the fire making is less too. The pump drill was successful at making fire too but because their were so many moving parts I had to try many times before it worked. Cords would break, the fly wheel would loosen and the drill kept jumping out of the socket. I spent an afternoon trying to get fire with it but it eventually worked. I would be more likely to use this device as a carpentry drill. It would be useful for drilling holes in timber that was going to be assembled with pegs. One thing I need to work on is the stone drill bits. They need to be fixed firmly to the shaft so that they are in line with the spinning action. If they are off a bit the whole drill wobbles.