Tag: wood joints

Types of wood joints

Types of wood joints

There are numerous ways to join pieces of wood.  Some are stronger than others, some are easier to do, and some require expensive machines.  The type and quality of joint you choose greatly affects the stability and durability of a project.  Today we take a look at some of the more common types of wood joints.  The images in today’s post are from a powerpoint presentation created by Tom Bockman, shop class teacher of 37 years.  We hope to make the entire presentation available on our website soon.

The goal behind making good wood joints is for the project to hold itself together with as little help from other means such as mechanical fasteners or adhesives as possible.  It is best to choose the simplest joint that will do the job the right way. Equally important is the appearance of the joint.

Clean tight joints can add a decorative effect to a project but not all joints can be seen.  Moistening the edges first will keep the wood from taking the water out of the adhesive.  Too little glue is known as a starved glue joint, too much is wasting glue. It is important that glue is applied over the entire edge so there are no dry spots.  A good glue joint will be stronger than the wood.

finger joints

A finger joint is a common woodworking joint. You use it to join two pieces of wood at right angles to each other. It is much like a dovetail joint except that the pins are square and not angled. The joint relies on glue to hold it together. It is a simplified version of the dovetail, and thus not as strong.

dovetail dovetail 2

Dovetail joints are very strong. The pins and tails are more trapezoidal instead of having 90 degree angles like finger joints.  After adding glue the joint is permanent and requires no screws or nails.

Dado (pronounced “Day-dough”) joints are commonly used for shelves and joins the edge or end of one board to the center of another. They’re also used in joining plywood together. A dado joint fits one part of itself into a slot on a second part of itself.   While the dado relies somewhat on adhesives, it has more gluing surface which will hold more glue along with a self supporting ledge which makes it quite strong. Dados are cut across the grain.

Rabbet joints are sometimes used to insert a back into a cabinet.  The rabbet joint requires fasteners (i.e screws or nails) and will keep the cabinet square.  It is much like a dado, except it is cut along the edge or end of the work piece. 

butt joints

Butt joints are made by taking 2 pieces of wood and butting them together.  The joint is weak and can be broken apart with your bare hands (ok, if you attach a metal bracket and some screws then maybe not).  The butt joint is commonly used in wall framing on construction sites. If you are a casual DIYer, this is possibly the only joint you have used.

The tongue & groove joint is strong.  This type of joint is cut along the edge and ends of the work piece, notched out into a groove.  When the boards are connected they cannot be separated unless one is lifted up at an angle.  This joint is very common with wood flooring.

The miter joint is used in picture frames and boxes, among other things.  To form a miter joint, the ends are cut at a 45° angle which creates a better surface area for adhesive to be applied as opposed to the similar butt joint.  Aesthetically, this joint looks much better than the butt joint due to the fact that the end grain is concealed.

 

A half lap joint is another common woodworking joint.  It consists of two parts fitting into each other in dadoes or rabbets cut half way into each half to form a flush fit.  They are strong, due to having more glue surface area and self supporting ledges.  When they fit together it should be flush. In a half lap joint, you remove material from each piece so that the resulting joint is the thickness of the thickest piece.  Half lap joints are good for making workshop storage items.

The mortise and tenon joint is a popular furniture construction technique, commonly used in table legs. A mortise is a cavity cut into a piece of wood to receive a tenon. A tenon is a projection on the end of a piece of wood to insert into a mortise.  The joint is self supporting with more surface area that holds more glue making the joint very strong. 

Dowel joints can be used to reinforce butt  joints.  Accuracy is extremely important, and partially for that reason biscuit joints are usually preferred to dowel joints.  Dowel joints are easy and faster to make than mortise & tenon joints.

A biscuit joint is another way to reinforce butt or miter joints.  The biscuit is made of dried and compressed wood, typically beech. They can be even faster to make than dowel joints.  Biscuit joints are commonly used in constructing cabinets and in making table tops and you will need to purchase a biscuit joiner.

While we have listed a basic overview of some very common wood joints today, there are others.  In the future we will be going more in-depth into the various types of wood joints.