This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
The principal parts of the combination lock are the five disks shown in Fig. 1. These are best made of sheet brass, about 1/16in. thick and 1 1/2, in. in diameter. The pins for turning the disks are each made A driving fit for a hole drilled through the metal at a point 15/32 in. from the center. Notches are cut in the disks C, D and E, Fig. 1, to receive the latch end, and the disk B is made like a cam, its use being to raise the latch into its keeper when the handle is turned backward. The disk A is without a notch and has only a pin for turning the other disks.
The disks are mounted on the inside of the drawer front in a U-shaped piece of metal, F, Fig. 2, which carries a 1/4-in. pin, G, as their bearing. The disks are placed on this pin with rubber washers, H, J, K, L and M, between them. These serve the purpose of preventing the disks from turning too freely. The disk A is fastened tightly to the end of the rod N, which is 1/4in. in diameter. The outer end of this Rod is fitted with a handle or turning head as desired. That shown at O is made of two pieces of wood screwed together, with a pointer, P, placed between them. A washer, R, is placed between the drawer end and the handle to take up any looseness and to allow the free turning of the rod.
A dial, S, is made of paper and the division marks and numbers placed upon it. The latch T is fitted in a U-shaped piece of metal, U, which is fastened to the inside of the drawer end where its heel will rest on the edges of the disks. When the right combination is made by turning the handle first one way and then the other, the latch will drop into the notches of the disks as they will be all in one place.
When the drawer is to be locked, turn the handle back from the last turn made for the combination and the latch will be driven upward into its keeper and the notches scattered so that the latch will not drop until the combination is again set.
The numbers for the combination can be found after the disks are in place and by turning the handle until the notch comes up to the place for the
heel of the latch. The number beneath the pointer is noted; then the next turned up in a like manner, all being done while the drawer is open and the disks in plain sight. The combination can be changed only by changing the location of the pins in the disks. - Contributed by C. B. Hanson, Fitchburg, Massachusetts.
Ill: The Parts as They are Attached to a Drawer Front to Make a Combination Lock