Specialty Table-Saw Blades

Two types of blades can be mounted on the table saw for specialty work, the dado and the molding cutter. Both require special setups and, in most cases, additional equip­ment. A larger table insert will be necessary to give the wider cutting surfaces of these blades adequate clearance where they break the plane of the tabletop.

You'll also need to protect both the blades and your fence by attaching a fence shield to the fence. A shop-made fence shield is easily made of scrap stock.

Dado Blades. The dado cuts rectangular recesses in wood. There are two types of dadoes. The less expensive (and some­what less precise) variety is called an adjustable or "wob­ble" dado. It is essentially a heavy-duty sawblade with a hub mechanism that allows it to be adjusted so that it spins at an­gles slightly less than perpen­dicular to the arbor. The resulting wobble of the saw-blade produces a cut that is wider than the saw kerf.

For more accurate work, a dado set or dado head is used. It consists of two outer circular blades, called grooving saws, sandwiching inner blades (the chippers). The outer blades cut the sides of the groove or rabbet while the chippers clear the center. Typically, the groov­ing saws are an eighth of an inch thick; chippers are usually sold in sixteenth, eighth, and quarter-inch thicknesses. A dado set will usually come with two grooving saws and several chippers. For fine adjustments of the width of a dado cut, shim washers can be inserted between the blades.

Dado sets are sold in diameters of six and eight inches. For most purposes, a six-inch set is quite adequate (and a lot cheaper).

Both the wobble dado and dado head are mounted on the arbor like a standard circular sawblade. When mounting a dado head, stagger the chip­pers; the teeth on adjacent blades shouldn't bind. Don't forget the alternate table insert (the plate that covers the mouth in the tabletop through which the sawblade protrudes) and to protect the fence with the fence shield.

To run the dado head, allow the saw to reach full speed. Once it does, present the work-piece gently: The saw will re­quire more time to cut a groove or rabbet because the sheer amount of waste being removed is greater than on a simple rip or crosscut. Use a push stick and, as always, wear your safety glasses or goggles.

The Molding Cutter. This de­vice cuts profiles in wooden stock, profiles that can vary from very simple to quite com­plex. The device consists of a steel cutterhead that is fastened like any other circular saw would be to the saw arbor of your table saw or radial-arm saw. The cutterhead in most molding cutters holds three identical blades with con­toured profiles; set screws hold the blades in place. Some mod­els use as few as one or two, but blade chatter is more likely with fewer blades, which make for a less well-balanced head.