Every woodworker, at some point builds 'cabinets'. They may not be true cabinets, but the follow that same basic process. They might be built in units, bookshelves, armoires, or actual cabinets. In any case, the heart of the process is pretty much the same - build a box.
These boxes are all built with the same techniques. They may get dressed up very differently but they start the same way. The root of this box construction is the dado joint. For those who don't know what a dado is, it is simply a groove cut into your stock that receives another piece of stock. A dado needs to be straight, square, and precisely the right width.
Over the years I have used and continue to use a variety of methods to cut my dadoes. Depending on the project, different methods offer different advantages. I will go through the 3 most common methods I use.
1) Table Saw with a stacked dado cutter. A stacked cutter in the table saw works well. Essentially, you pile up several blades and chippers on the arbor of your saw (see my article on a cheaper alternative to an expensive dado set here.) With careful measuring and a few test passes you vary the head width until it is precisely the width of the stock your work will receive. This method works well with pieces going through the saw lengthwise. Most cupboard size cabinets are easy enough with this method. However, I have always found it awkward to cut dadoes perpendicular to a long piece. Bookshelves are a good example of long narrow boards that are difficult to cut this way.
2) The stacked dado on the radial arm saw. Built in the same manner as with the table saw, putting the dado head cutter on the radial arm saw is the opposite component of that method. The radial arm saw is fantastic for cutting dadoes across a narrow but long piece. The drawback is that it has a limited cut length.
3) For those without the radial arm saw or even a dado head cutter, there is always the go to tool of the workshop - the router. The router is the most versatile dado cutting tool of all. It easily makes stop dadoes (dadoes that don't reach the edge), and can be quickly set to cut any depth. The use of a clamp on straight edge and some very careful measuring produces excellent dadoes.
There is a drawback to the router though. When I was younger, all wood was precisely the same width. Plywood came in 3/4, 1/2, 5/8, etc . . . this is no longer true. In recent years the thicknesses have started to come slightly undersized. I suspect this is due to the influence of the metric system. This does, however, leave us woodworkers with a problem. If we use our 3/4" router bit to plow out a dado, then it will be slightly too large. There are really only three solutions: go buy a metric router bit, if you can find one; or make two passes with an undersized bit. The first is difficult to do because the bits are difficult to find. The second requires an enormous amount of care and precision. The third solution is to cut a dado undersized and then trim down the stock going into the dado much like a tenon. Since this is sometimes done anyway, it can be a simple process, however, when it is unnecessary it can be a tiresome amount of extra labor.
Those three methods make up about 95% of the dado I cut. There are some other ways, including the old fashioned chisel, but these are so rarely used that I don't think they are worth detailing.
Good Woodworking.
