The following instructions provide a construction process for a coin bank using a USPS PO Box door manufactured by the Federal Equipment Company in 1966. Other varieties of doors are available that may have different dimensions. The wood used to build this example is 1/2″ 1/4″ thick oak and a purple heart corner groove inlay. Variations in construction and materials are easily adopted and some suggestions will be noted throughout the step-by-step instructions that follow.
Step One: Determine Box Dimensions
The inside surface of the door has screw holes, perpendicular to the face, which are used to fasten the door to the body of the box. The position of these holes dictates the dimensions of the door opening. A good approach to determining the top, bottom, and side dimensions of your box is to lay two 1/2-inch pieces of material, parallel to each other. Lay the door face up with the top and bottom parallel to the pieces of wood. Move the pieces of wood until they are parallel and fit just outside the screw holes on the inside of the door. Measure the distance between the outer edge of each 1/2-inch piece of wood. This measurement is the length of the two sides of the box.
Repeat the process above, but position the top and bottom of the door perpendicular to the pieces of wood. Measure between the outer edges of the pieces of wood again. The result is the length of the top and bottom of the box.
Step Two – Cut Out the Box Frame Pieces
The top, bottom, and side dimensions determined above represent the outside height and width of your box. The depth of your box is optional. The depth (distance from front to back) is determined by the width of the material you choose. The type of joint you choose to join the box frame will determine how you will cut the pieces. For a simple miter joint, make the cuts at a 45 degree angle. For box joints or dovetails, cut at a 90 degree angle. Making box or dovetail joints is outside the scope of these instructions.
Step Three: Trial Fit, Pilot Holes. Coin slot and assembly
After cutting, try on your box frame. Place the door inside the front face and verify that the door fits correctly. The critical test is to determine that the door will fit inside and allow for full corner joining. Also check that the edges of the door overlap the surface of the front face. A bit of play is fine because you can adjust the position by securing the door screws later. Mark the position of the screw holes on each side piece. Drill pilot holes that will accept #6 X 3/8″ sheet metal screws.
Make a coin slot in the top piece of the box. If you choose to include an inlay in the coin slot, please complete that process now. If you are using a brass coin slot cover, put it on as the last step. Glue your pieces together and secure with clamps.
Step Four – Cut and Join the Back of the Box
While one option is to route a hole in the back of the box, the simplest method is to cut a 1/4″ back piece of material to the dimensions of the box back. Whichever method you choose, make sure the box back to the box frame with screws and/or glue.
Step Five: Determine and Record the Door Combination
The door combination is revealed by turning the knob and recording the position of the letter of each turn to the right, left or right. Watch the inner cups at each turn and stop when the red marks line up with the top mark. Check that the combination is correct by turning the center knob on the front to open the door. Record the letter combination.
Sixth step: mill, sand and finish
At this point, you can optionally mill the edges of the box with a round bit. Sand the body of the box and apply your favorite finish. I have used natural danish oil with good results. Once the finish is dry, screw down the door and fit a brass coin slot plate, if used. Your bank is now complete. A series of photos of these instructions and doors are available from Herzercraft.