A router is essentially a high speed motor with a high-speed rotating spindle, to which you can attach a larger variety of cutting bits that can create thousands of different decorative profiles. A router can also be used to make structural joinery cuts, such as rabbets and dadoes, mortises and tenons, and dovetail joints.
The router motor is clamped into a flat base with an opening it in, through which the cutting bit extends. With the motor running and the bit spinning at high velocity, running the base of the router along a workpiece allows the bit to cut a shaped edge with remarkable ease. Even if you own only a few bits, you can create hundreds of various shapes by varying the depth of the bit.
The router is a mainstay power tool of the modern wood shop. The tool is normally used in a handheld fashion, but it can also be mounted upside down on a router table, allowing you to shape wood by sliding the workpiece along a cutting bit extending up through the table.
Many woodworkers own two or three different routers with varying horsepower levels and different features. Whether you prefer a fixed-base router or a plunge router, there are a number of features you should learn about when purchasing a router for your shop.
The motor spindles on both fixed-base routers and plunge routers are fitted with collets that can hold a variety of router bits. An almost infinite number of edging profiles can be achieved using specialty bits, or by using a combination of bits in multiple cutting passes. Most beginning woodworkers can get by with ten versatile router bits that will complete the most common tasks.
A good router bit can create a variety of different cutting profiles, and with hundreds of different bits available, your cutting options with a router are almost limitless. But no router bit will cut properly if it is not correctly installed in the tool's collet. An incorrectly installed bit can vibrate excessively (called chatter), which at best yields a rough cutting profile, and at worst can be quite dangerous to the user. Learning to properly install your router bits does a long way toward ensuring safe, efficient results.
As you become familiar with certain router bit profiles, you may recognize that the same cut can be created by several different bits. For instance, a straight cut, can be made with straight bits with one or more straight cutting flutes, but the same straight cut can also be made with spiral bits with either upward or downward angled cutting flutes. There are certain advantages to each type of bit, however, and it's important to learn their different qualities and which one to choose for each job.
One of the most troublesome problems when routing is the tendency of wood to splinter or tear out—a problem that is especially common with strongly grained woods, such as oak. Splintering is sometimes just an annoyance, but large tear-out splinters can ruin a workpiece. You can usually avoid this problem by choosing the right cutting bits and maintaining them correctly, and by using proper technique when using your router. Using a dull blade and feeding the tool too fast, for example, will very often lead to splintering. Learn various methods for avoiding splintering during your routing work.
Most router bits come in either a 1/4-inch or 1/2-inch shank. Better routers often come with a collet for each shank size, allowing you to change out the collet so you can use bits of either size. For lightweight work, such as light edge profiles or work on softwoods, 1/4-inch shanks are usually just fine. But for heavy-duty work on hardwoods, mounting your router with a 1/2-inch collet will create more stability and smoother cutting. Learn the advantages of each shank size.
The dovetail joints that are the hallmark of the finest woodworking projects were cut by hand with precision saws for centuries, but most of today's woodworkers use a router with a specialized dovetail jig to do this work. Not only is this method far quicker, but it is considerably more precise than trying to cut the pins and tails of dovetails with a handsaw.