The bottom of the drawer holds the contents of the drawer from falling out and onto the floor. The construction of the bottom is important so the journey to the sides is sufficient for the weight the drawer will hold.
Most generally, drawer bottoms are housed in some type of grove that has been cut into the sides, front and sometimes the back of the drawer. This is good if the groves are cut at the proper depth. If the grooves are too deep or too wide they will compromise the strength and stability of the sides of the drawer.
A drawer slip is an excellent alternative to the drawer groove. The drawer slips are small square strips of wood that are glued to the inside of the drawer at the bottom edge. The grooves are then cut into the strips to eliminate any type of compromise to the drawer structure itself. The slips provide an additional benefit by increasing the bearing surface of the drawer to help extend it’s life.
The two basic woods used for the bottom of the drawers is either plywood or a solid hardwood. In today’s society, plywood seems to be the wood of choice. Plywood is very strong at whatever thickness and it is stronger than a plain piece of wood. Because of the way plywood is made, it may be glued into place where hardwood needs to have the ability to expand and contract. By gluing the bottom of the drawer in place it adds stability and strength.
A drawback of plywood is it’s thickness. A normal ¼ inch piece of plywood actually measures 7/16th of an inch. When making a groove that is ¼ inch wide, the bottom may rattle even if glued. It is best to use a smaller router bit and make two passes to get the groove width as close to 7/16th of an inch as possible.
When using a solid hardwood it is best to use a thickness of ½ inch. The ¼ inch has a tendency to crack. The thickness of the bottom hardwood board depends on the size of the drawer. Small drawers can use ¼ inch wood, while a little larger drawer may need 3/8 inch.
To prepare the drawer for the hardwood bottom requires a rabbet or tongue. This is used to help reduce the width of the groove required for insertion. Use a router with a panel-raising bit to form the tongue on the bottom board that is needed to fit the grooves.
It is important to use a open-back construction when using a hardwood bottom. The wood needs room to contract and expand. Place the bottom in the drawer so the grain goes from side to side, which is parallel to the back. Use a screw or nail on the outside of the back of the drawer to secure the bottom in place yet allowing it room to expand or contract.
When a drawer is going to be very wide it is necessary to use a muntin to help support the bottom. The muntin may either be placed under the bottom so one large piece of hardwood may be used inside the drawer or it can be placed in the middle of the drawer and grooved. In this case, two panels of hardwood would be used to make the bottom of the drawer.
A solid construction of the bottom of the drawer will ensure a long life for the drawer. Using the proper width of wood will prevent cracking.