When building cabinets one of the best ways to make a clean strong joint in the face frame is the use of biscuit joinery.
Let me start out with a brief explanation of what biscuit joinery is, a biscuit, in this context, is a small oval piece of wood about 1/8 inch thick and comes in varying lengths. Of course you will need a biscuit joiner as well, this is a power tool that has a small circular saw blade that cuts into the edge of a piece of wood to the proper depth and shape to accept the biscuit.
As in all building projects it is necessary to layout all your components and align how, where and by which method each piece will be joined with another. The use of biscuit joinery when building cabinets is mostly in making the face frame, that portion where the hinges and latches are attached to the final cabinet. You have the choice with biscuits joints to make them either mitered corners or butt joints; the use of biscuits adapts itself easily to either type joint.
After you have built your cabinet box (es) using standard, screw, glue and nail carpentry you are ready to face this/these basic box (es). Measure the perimeter of the box units for the application of the face frame; having done so and being assured that all measurements are accurate, cut the components of the face frame and lay them out on a flat level surface as the final frame will appear when joined and ready to assemble to cabinet boxes. You will have a loose formation of stiles and rails. Stiles are the vertical pieces of the frame and rails are the horizontal.
Dry fit all the pieces of your frame and check that they fit each other smoothly and flush with no burred edges or gaps. At the points that you will be making your joints, i.e.: corners, center stiles and or rails, etc., line up the component pieces exactly as you will have them in a finished product. Establishing the exact center of the component whose end butts to the matching piece in butt joints, or where the mitre joint components meet, using a straight edge mark a line with a pencil on both components where they will be joined. In the case of a mitre joint the end center of each component. Repeat this process at each point that a joint of either type will be established.
Mark each component as to its relationship to the finished product to assure that each piece is properly relocated in relationship to you original layout. Each in turn, clamp your component pieces to a work table, be sure to clamp between table and a soft piece of scrap wood so as not to leave clamp marks on the surface of your components.
Using your Biscuit Joiner (saw) align the center indicator on the face of the joiner flush against the component piece and inline with your pencil mark and plunge cut the edge of the component as instructed in the safety instructions that come with the joiner.
Always remember whenever using any form of power tool, be safe, wear protective eye covering as sawdust and wood chips will be flying around, be sure you are standing in a clear, dry and clean area to avoid slipping and always, always be aware of your surroundings for any possible hazards. Do not wear loose clothing, long sleeves should be buttoned or rolled up tight to avoid possible contact and tangling with moving parts of power equipment, and shirts should be tucked into your waist, not flapping loosely around your body.
Now that you have your joints cut and grooved for biscuits, working on one joint at a time, slip a dry biscuit in one side of each joint and fit the components together forming the basic face frame.
Starting with the top rail, apply carpenter’s glue to the interior of each joiner cut and lightly brush each biscuit with carpenter’s glue and assemble first the two corner joints and then the center stile joint (s) and clamp. Moving swiftly repeat this procedure on the lower rail joints. Once all are joined with glued pieces and clamped, with a damp cloth wipe off any excess glue that forms on the exterior of your frame and then measure the frame diagonally corner to corner, each measurement should be exactly the same, if not it means you are out of square and adjust the pressure of your clamps until and with a dead blow hammer lightly tap the longer measurement corners and re-measure until you obtain the even measurement between opposing corners. At this point your frame is square, you can check your stiles using a carpenter’s square to assure that they are square and perpendicular to the rails.
Allow the clamped unit and/or units as the case may be to sit clamped over night to assure that the glue is dry and your joints are tight. Taking care loosing the clamps, once dried; lightly sand the exterior face of the face frame with 220 grit paper either by hand or with an orbital or palm sander. This will clean all pencil marks, glue residue and other possible blemishes from your frame and assure a smooth transition of components at each joint. Turn frame over and repeat on interior side.
All done? Congratulations, you are ready to assemble face to your cabinets. Good luck and happy building.All done?