twist drill

Instead of using an ordinary twist drill, a special hollow drill may be obtained from the Universal Battery Co.

He had decided to tell of the lunch-box and twist drill episode, but to say nothing, for the present, of the strange white fire.

Twist drill bits will bore both wood and iron, and they are not expensive up to three-eighths inch or one-half inch.

This drill will go through a wall almost as quickly as a twist drill and with much less labour.

Bore it with a twist drill, or nosebit, to the depth of an inch and a half.