Router bits can be used with fixed base routers, plunge routers and shapers to apply edge profiles to wood stock. In many cases, a series of router bits can be used to apply a complex shape, whether to dress up the edge of a single board or to create some custom molding. In most cases, one or more of the following ten basic router bit shapes can be used to create these edges:
A beading bit is similar to a roundover bit (below) in that it applies a rounded shape to the edge of the stock. The difference between a beading bit and a roundover bit is that the beading bit also cuts a square shoulder on the top and bottom edges of the roundover. Beading bits often have a bearing tip for riding along the edge of the stock as it is cut.
A chamfer is a 45-degree angled cut on the square edge of a piece of stock. Chamfer bits are versatile, in that one bit can create several different-size chamfers based on the depth of the cut. As with the beading bit, some chamfer bits have a bearing-tip that rides along the edge of the stock.
A cove profile is designed to apply a concave, rounded profile. Often, the cove bit is used to match a beading or roundover shape on the corresponding piece of stock. For instance, drop-leaf tables use matching cove and bead profiles (called a rule joint). The cove bit often has a bearing-tip for riding along the edge of the stock. Tip: The cove profile is not to be confused with a round nose bit (below), which is used to make round-bottomed grooves in the middle of a piece of stock.
Dado (Straight-Cutting) Bit
There are several methods that can be used to cut a dado profile, which is a square channel in the middle of a piece of stock. While there are specialty saw blades used for cutting dadoes on a table saw, a dado can also be cut with a router using any of a variety of straight-cutting bits. These straight-cutting bits come in a variety of sizes, they are all similar in that the bit is designed to cut a flat bottom and square sides. Some straight-cutting bits have a bearing-tip (designed for trimming a piece of laminate applied to the face of a board), but these bearing-tip bits cannot be used for cutting a dado.
The dovetail bit is most famous for use in creating tails for dovetail joinery. However, dovetail bits can also be used to make tapered dadoes and rabbets. A dovetail profile has a flat bottom with angled sides which are wider at the base. Most dovetail bits do not have a bearing, although a few specific template-style dovetail jigs require bearing on the shank of the bit.
The Ogee bit, also referred to as a Roman Ogee creates a compound, S-shaped profile. There are several variations on the Ogee profile, with shoulders on the edges or points in the middle of the profile. As with other edge bits, Ogee router bits often come equipped with a bearing tip.
Simply stated, a rabbet is a dado on the edge of a piece of stock. While rabbets can be cut using a table saw (with a dado blade) or a straight-cutting router bit, there are also specially-designed rabbeting bits, designed to ride along the edge of the stock (often with a bearing tip).
Round Nose Bit
The round nose router bit is similar to the cove bit, except that it is designed for plunge routing grooves and flutes in the middle of a piece of stock. Round nose bits, sometimes referred to as core-box bits, can be used to cut shallow, rounded-bottom grooves of various depths, but to be used properly, the bit should be plunged until the profile cut into the wood creates a full 180-degree arc.
As mentioned above, the roundover bit creates a rounded profile on the square edge of a piece of stock and differs from the beading bit in that no shoulders are cut. Often, only a portion of the roundover bit is used to create a partial easing of the edge rather than a full 90-degree arc. As with beading bits, roundover bits sometimes have a bearing tip.
Think of a V-groove profile much like a double-chamfer profile to be plunged into the center of a piece of stock, similar to the way the roundnose bit is used. In this case, however, the profile is a V-shape in the stock. The V-groove bit can be used at various depths to create grooves of a variety of different widths.