Published on June 30th, 2011 | by Dylan Linet1
Woodworking: Creating Basic Splices and Wood Joints
Old fashioned wood joinery is an art that has been slowly fading from mainstream life since the invention of metal gusset plates. Back when buying hand forged steel was more expensive than cutting a timber from your back yard and hand hewing it it to fit, all framed houses used wooden joinery. Aside from saving materials and providing comparable structural stability, wood joinery just plain looks better and adds an element of style to any wood connection.
Now, with more and more people starting to return to building their own homes, there has been a resurgence of interest in how to build while minimizing the amount of metal used. Below is a handful of some simple, as well as some more complex types of wooden joinery.
One of the most famous and referenced types of wood joinery is the mortise and tenon. A simple design that has countless variations, the mortise and tenon has been used for thousands (yes thousands!) of years to create strong 90 degree angles. In it’s most basic form, a piece of wood is narrowed into a slim rectangular prism at one end. this cut is often done with simple hand saws.
A rectangular hole is then cut to size into the receiving piece of wood. This is done using a drill to make the initial hole, and then widening and shaping it with a chisel. When completed, the rectangular prism (the tenon) fits into the hole (the mortise). The diagram below illustrates the concept, with the addition of wedges to hold the tenon in place.
The T-bridal Joint
An interesting an elegant joint, the T-bridal joint is a cousin of the mortise and tenon. Used to attach one member to the middle of another, the T-bridal is often used in railings and benches. Although it performs excellently against downward compression, this joint, due to it’s thin connecting plates is not suitable where large amounts of shear are present. In the diagram below, you can see that the mortise is open on one side to allow the tenon (which is in the middle of a crossbeam) to slot in.
Splice joints are used when the length of a given timber needs to be extended, but longer timbers are not on hand. There are many designs for splice joints, but the basic idea is this: Joining wood by simply gluing the ends together is an extremely weak joint. This is partly because of the small surface area being joined, and partly because the ends of wood (due to the orientation of the grain) do not glue together well. In order to avoid this problem, a parallel or nearly parallel gluing plane is created, and this becomes the main structural bond. These simple joins are often easily cut out with a hand saw, and once glued are quite strong. The diagram below illustrates the differences between some of the more common splice joint types.
These are only a few examples of the many types of old fashioned wood joints. Most of these joints can be improved with the addition of wooden dowels or modern screws to hold them in place. If you want to learn more about types of wooden joints, or have a question or comment, write below!