This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
These are only magnified gimlets for use with both hands. They are represented in Fig. 3S0, a being the "twisted," and b the "shell" form. A wooden bar is thrust through the eye c, and the hands exchange ends of this bar at each half revolution given to the tool. Their sizes advance 1/8 in. at a time from 3/8 in. to 2 in. in diameter, and prices range from 8d. to 6s. 6d.