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. There are other varieties of doors available that may have different dimensions. The wood used to construct this example is 1/2″ and 1/4″ thick oak and a purple heart coin slot 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, that are used to attach the door to the box body. The position of these holes dictate the dimensions of the door opening. A good approach to determining the top, bottom, and side dimensions of your box is to lay two pieces of 1/2 inch stock, parallel to one another. Place the door, face up with the top and bottom parallel to the wood pieces. Maneuver the wood pieces until they are parallel and fit just outside the screw holes on the inside of the door. Measure the distance between the outside edge of each 1/2 inch wood piece. This measurement is the length of the two sides of the box.
Repeat the process above but place the door top and bottom perpendicular the wood pieces. Measure between the outside edges of the wood pieces again. The result is the length for the top and bottom of your box.
Step Two: Cut 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 stock you choose. The Joint type you choose to join the box frame will determine how you cut the pieces. For a simple miter joint, make your cuts at a 45 degree angle. For box joints or through dovetails, cut at a 90 degree angle. Making box or through dovetail joints is outside the scope of these instructions.
Step Three: Test Fitting, Pilot Holes. Coin Slot and Assembly
After cutting, test fit your box frame. Place the door inside the front face and verify that the door fits properly. The critical test is to determine that the door fits inside and allows for the complete joining of corners. Also verify that the door edges overlap the surface of the front face. A minor bit of play is alright because you can adjust positioning when 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.
Rout a coin slot into the top box piece. If you choose to include a coin slot inlay, complete that process now. If you use a brass coin slot cover, attach that as your last step. Glue your pieces together and secure with clamps.
Step Four: Cut and Attach Box Back
While an option is to rout a recess in the back of the box, the simplest method is to cut a back piece of 1/4″ stock to the dimensions of the box back. Regardless of the method you choose, secure the box back to the box frame with screws and/or glue.
Step Five: Determine and Record Door Combination
The door combination is revealed by turning the tumbler knob and recording the letter position of each right, left, right turn. observe the inside tumblers on each turn and stop when the red marks align with the top mark. Verify the combination is correct by turning the center knob on the front to open the door. Record the letter combination.
Step Six: Rout, Sand, and Finish
At this point you can optionally rout the box edges with a round over bit. Sand the box body and apply your favorite finish. I have used natural Danish oil with good results. Once your finish is dry, screw on the door and attach a brass coin slot plate if used. Your bank is now complete. A photo series of these instructions and doors are available at Herzercraft.