Groove and Dado Joints

 

A dado (AKA housing or trench) joint is a U-shaped, square-bottomed channel cut across the grain.

A groove looks just like a dado, but runs with the grain. 

*the photo above shoes a through-dado and through-groove; a stopped dado is shown below

*a "blind" dado or groove is not visible once assembled, useful for certain aesthetics and applications

What are their application to cabinetmaking? How many different ways can these joints be used?

Some common uses for dado/groove joints include the rails and stiles of doors, the shelves and gables of a bookshelf or cabinet, picture frames, and cabinets, boxes or drawers more generally, e.g. frame and panel. 

History

In architecture, the dado is the lower part of a wall, below the dado rail and above the skirting board. The word is borrowed from Italian meaning "dice" or "cube", and refers to "die", an architectural term for the middle section of a pedestal or plinth. It seems that both joints are relatively new, with multiple sources saying the first recorded dado or groove joint occurred in the 19th century - but that could be wrong.

What tools are required to produce this joint? Are there many ways to go about it?

Both joints are typically made with either a router (hand or or a table saw with a dado set. You can also cut them by hand, with chisels and a router plane, and sometimes a handsaw. For a stopped dado or groove especially it is useful to use a jig, stop block or fence depending on your set up to make consistent cuts.

An example method of creating a groove joint: 

How do they stand up to common stressors?

A properly made dado/groove will be stronger than either of the boards it is joining. If improperly done, it can weaken a board and cause it to break along that line, or it can sag between joints if not properly supported. 

What role do materials play when making this joint? 

You can make this type of joint with any material - solid wood, modern materials like plywood, metal, etc. Depending on the application, you may want to leave wiggle room for wood movement.

Was there anything significant that occurred to you during this experience?

We reconsidered our life choices, but that happens all the time.

What do you think are the joints' role in the modern world of cabinetry?

Grooves and dadoes are types of traditional joinery, using no hardware or mechanical fasteners. They are a relatively strong strong joint, and fail when they aren't properly supported, e.g. a very long shelf with no center support can dip over time. They can be visible, for a "craftsman" look, or blind, for a cleaner aesthetic. They can be glued for strength and stability or left as-is, like in shelves that slide out for disassembly. It seems that whether they would be used in a permanent, high end project or a temporary and cheap one, dado and groove joints are very useful in the modern world.

Personal reflections

Alanna: I realized a lot of information online in woodworking or cabinetmaking is not well-written, which is a shame because communicating information well is so important for making it accessible. I'm curious if there are more reliable resources to read from other than Jim So-and-so's blog or a website that sells woodworking courses for $80 USD each.