The Ticket Punch: Shearing a Hole, and Catching the Chad

The lower jaw A of the punch is split at its end into an upper portion a and a lower portion b by a horizontal slot c "in which slot the ticket to be punched is inserted." The upper jaw d pivots on it "in the usual well known manner" and carries a removable punch section e which, when d is pressed, enters "the conical hole f" in portion a "and to cut the ticket against the cutting edge g thereof." Brooks notes that this form of punch is well known. His addition is a receptacle or box h fitted over portion a, with an aperture i "of smaller diameter than and coinciding with" hole f. Prongs on its sides bend under the jaw to hold it on. The clippings "are prevented from flying over the floor and furniture of the car" and are kept until "a suitable place and time" to empty them, and the aperture "enables the conductor to see the ticket before it is punched".

Punch holes through one sheet of paper, then stacks of 5, 10 and 20, and through a strip of card stock. Hook the spring scale to the end of the punch's handle and pull until it cuts: that force times the lever ratio is the punch force. Compare with the notebook and work out the paper's shear strength from your readings. Look at the edges of the holes under a hand lens: a sharp punch with a small clearance leaves a clean edge; a worn one tears and leaves fibres. Save the chads in a box, as Brooks did, and count them.

**Charles B. Brooks** of Newark, New Jersey, filed on 10 January 1893; US 507,672 is dated 31 October 1893. It claims a ticket punch whose slotted jaw carries a removable receptacle with an aperture smaller than, and in line with, the punch hole. **Honest limits.** The shear strength of paper varies widely with grade and humidity; the figure in the notebook is an assumption to be replaced by your measurement.