Jointery

 

Putting Wood Together/Wood Joinery: Philosophy and Snob Bashing

 This is a very touchy subject for many if not most wood workers. This is where you find out how “snobbish” other wood workers can be. In many circles your worth as a craftsman is often inferred by how you put wood projects together, or in other words the types of wood “joints” that you use. I believe this to be true rubbish! Do not let the snobs bother you! Be concerned with strength, accuracy, longevity, and also simplicity. Forget about status as long as the other four conditions are met.

 At CHS we use a lot of wood screws to assemble (put together) wooden projects. Status wise in the wood working world this is comparable to dining frequently at McDonalds. However, McDonalds has nice, simple, and inexpensive food. In addition they can always be counted on to have clean restrooms and great coffee. How can you do better than a double cheeseburger for a buck? Snobs take great care in explaining that they never go to McD’s, as though it is beneath them. They also take great care in explaining that they never use metal fasteners to put together their projects, because they are simply superior to the rest of us rabble. They would rather spend much more time and effort crafting a fancy wood joint that will not be as strong nor last as long as using wood screws.  Properly installed wood screws should last a thousand years. Dowel rods usually last no more than 20 years…and the coffee there tastes like dirt!

 We sometimes use dovetail joints because they are strong and look cool. They are also fast, efficient, long lasting, and easy to do, along with the high status. We also use mortise and tenon joints when it makes sense to do so in a big table or in a chair. Here strength is very important and screws simply cannot deliver the goods nearly as well. Miter joints are also often used for traditional reasons, but you can bet that we reinforce them with our friend the steel wood screw! On the lathe we produce tenons as part of projects. Yep, on the lathe tenons make a lot of sense, are easy, fast, accurate, and simple. Better use a screw to hold it or it will not last longer than 20 years though!

 Mitering the sides of boxes is dumb, as there is almost nothing there to glue. Biscuits are for breakfast and not for your cabinet. Biscuits do not pull anything together, but may in fact help push stuff apart. Biscuits are under pressure, so they can cause swelling and deformation. A 3/8” dowel is much weaker than a screw. Try breaking a screw with two hands! Dado joints in cabinets are cut halfway through the sides of the cabinet. This takes away half of the thickness of the side, logically losing you more than half of the strength of the wood. What could possibly go wrong there? Pocket hole screws get rave reviews but they rely on expensive clamps, drills, and specific screws.

 The following is a very good list of joints, along with classic examples of wood worker snobbery:

 

Edge joint Edge Joint
The edge joint is also a very weak joint, similar to the butt joint, but in this case the edges of the wood are joined together. This type of joint is used to expand the board width for making table or desk tops. It is typically strengthened by first jointing the edges, and then using dowel pins and glue. If the joint is not going to incur much stress, then a spline can be used to strengthen the joint instead of dowel pins. This would require cutting a groove in each of the edges and gluing a wooden spline into them. To prevent cupping, alternate the end grain pattern of each board.

 

Miter Joint Miter Joint
The miter joint is made by joining two boards together at the corner to form a 90 degree angle. This is accomplished by cutting the end of each board to a 45 degree angle. The miter can be cut using a table saw or a radial arm saw. But for more accuracy a power miter saw should be used. Miter joints eliminate the exposure of end grain, and are primarily for framing, such as for picture frames. Miter joints are also very weak, and are commonly strengthened by adding a spline or a biscuit. A blind spline is usually preferred because it is concealed within the joint. This is accomplished by cutting a groove part way in the adjoining members, and then a wood spline is glued into the joint. The biscuit is a small, thin oval shaped piece of wood that is inserted and glued into the joint. A biscuit cutter is used to cut grooves for the biscuit.

 

End Lap Joint End Lap Joint
The end lap joint is another simple joint that can easily be made using a dado blade on a table saw or a radial arm saw. This can be accomplished by removing the width and half the depth of each board and joining them at a 90 degree angle. This joint is primarily used to frame the corners of projects. Other variations of the end lap joint include the cross lap joint, the edge cross lap joint and the middle T lap joint. Each of these joints are shaped by the same technique, but are used for different purposes. These joints can be strengthened with metal fasteners. In many cases, unless the joints will be under a great deal of stress, no additional strengthening is required.

 

Rabbet Joint Rabbet Joint
A rabbet joint is made by cutting a dado on the end of one board and fitting another board into the dado. The dado can be made by using a dado cutter on a table saw or a radial arm saw. The width of cut should be equal to the thickness of the adjoining board and the depth of cut should be one half its thickness. This joint is typically strengthened using staples, nails, or wood screws. The most common uses of a rabbet joint are for making drawers and boxes. When making boxes, both dados and grooves are usually required.

 

Dado Joint Dado Joint
A dado joint is made by cutting a dado, across grain, where needed other than on the end of the board. It is typically made by using a dado cutter attached to a table saw or a radial arm saw. The width of cut is equal to the thickness of the board to be inserted into the dado. The depth of cut is one half the thickness of the board being cut. Dado joints are commonly found in bookcases or cabinets, or wherever shelving supports are required. This type of shelving is permanent, so trim is usually attached to the front of bookcase or cabinet to improve its appearance.

 

Lap Dovetail Joint Lap Dovetail Joint
The Lap dovetail joint requires the use of a router with a dovetail bit, a dovetail jig and a template. The ends of two boards are held in place using the dovetail jig. The router cuts the dovetail joints in both pieces of wood. The template will determine the exact placement of each dovetail that is cut. The dovetails are tapered to provide a very strong joint by slipping the sides onto the drawer front. These joints are typically used for expensive drawer construction, where a solid drawer front is required and only the sides of the joint are visible. Also, dovetail joints can be made manually, by drawing the shape and size of each dovetail onto the wood, and then cutting them with a back saw. This is a laborious process and the joint precision is usually not as accurate compared to the router/jig method. A couple of variations to the lap dovetail joint include the through dovetail joint, where the sides and fronts of the joint are visible. The blind dovetail joint is just the opposite, where the tails and pins of the joint are completely concealed. Expensive trays, boxes and small chests are usually made with this type of joint. Dovetail joints are considered one of the strongest joints used in for woodworking, and when glued, no additional strengtheners are required.

 

Finger Joint Finger Joint
The finger joint is similar to the dovetail joint, but is much simpler to make. No router or dovetail jigs are required. Also, the finger joint is cut straight rather than tapered like the dovetail joint. It can be cut using a dado cutter on a table saw or a radial arm saw. The fingers should be cut to uniform sizes on each adjoining board. They should also be offset so the two boards will properly fit together. The depth of cut should be equal to the thickness of the boards. This joint is typically used for box construction. It is also used for drawer construction, where a solid drawer front is attached to the box face so that only the finger joints are exposed on the side of the drawer. This is a strong joint, and nothing more than glue is usually required for strength.

 

Blind Mortise and Tenon Joint Blind Mortise and Tenon Joint
The blind mortise and tenon is a very strong joint. Its primary use is for leg and rail construction. The tenon is cut on the ends of the rails, and the thickness should typically be cut equal to ½” the thickness of the stock, for stock thicknesses up to one inch. For stock thicknesses over one inch, the tenon thickness can be proportionately less than the one half the percentage previously suggested. Also, it is recommended that the tenon be ¾” long. The tenon can be cut using a dado cutter on a table saw or a radial arm saw. The mortise is cut into the legs using a mortise machine. The mortise should be cut to the same dimensions as the tenon, except that the depth of the mortise should be 1/8″ deeper than the tenon length. In most cases just gluing and clamping will suffice. But if additional strength is needed, a wooden pin can be used. The blind mortise and tenon joint is considered the most common, but other variations such as the barefaced, open, through, and angled are also used, depending on the situation or desire.