The following instructions provide a construction process for a coin bank using a USPS mailbox door manufactured by Federal Equipment Company in 1966. There are other varieties of doors available that may have different dimensions. The wood used to build this example is 1/2 “and 1/4” thick oak with a purple heart shaped 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 the dimensions of the box
The inner surface of the door has screw holes, perpendicular to the face, which are used to secure the door to the body of the box. The position of these holes determines the dimensions of the door opening. A good approach to determining the top, bottom, and side dimensions of your box is to place two 1/2-inch pieces of paper, parallel to each other. Lay the door face up with the top and bottom parallel to the pieces of wood. Maneuver 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 outside edge of each 1/2-inch piece of lumber. This measurement is the length of the two sides of the box.
Repeat the above process, but position the top and bottom of the door perpendicular to the pieces of wood. Measure again between the outer edges of the pieces of wood. The result is the length of the top and bottom of your 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 gasket 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 dovetails, cut at a 90 degree angle. Making a box or dovetail joint is outside the scope of these instructions.
Step Three: Trial Fit, Pilot Holes. Coin slot and mounting
After cutting, test the fit of your box frame. Place the door inside the front face and check that the door fits correctly. The critical test is to determine that the door fits on the inside and allows complete joining of the corners. Also check that the edges of the door overlap the surface of the front face. A little play is fine because you can adjust the position when you secure the door screws later. Mark the position of the screw holes on each side piece. Drill pilot holes that accept # 6 X 3/8 “sheet metal screws.
Place a coin slot in the top box piece. If you choose to include a coin slot inlay, complete that process now. If you are using a brass coin slot cover, attach it as the last step. Glue your pieces together and secure with clamps.
Step four: cut and replace the box
While one option is to cut a hole in the back of the box, the simplest method is to cut a 1/4 “back piece of stock to the dimensions of the back of the box. Regardless of which 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 tumble dryer knob and recording the position of the letter of each turn to the right, left and right. watch the inner cups at each turn and stop when the red marks line up with the top mark. Check the combination is correct by turning the center knob on the front to open the door. Record the letter combination.
Step six: milling, sanding and finishing
At this point you can optionally route 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 your finish is dry, screw on the door and attach a brass coin slot plate if used. Your bank is now full. A series of photos of these instructions and doors are available from Herzercraft.