The dovetail joint is a utilitarian and reliable way to join wood together. Its superior strength means it doesn't require adhesive or mechanical fasteners for reinforcement. Because they don't lose structural integrity when wood naturally expands and contracts, dovetails are often used to join large pieces together, such as the panels that comprise cabinet or chest cases. Dovetail joints usually indicate a high level of craftsmanship because they demand a lot of time and skill to execute properly. Using a router and a dovetail jig can significantly reduce the amount of effort it takes to create a tight-fitting joint.
"Through" and "half-blind" are the two basic types of dovetail joints. The half-blind dovetail profile is only visible on one side of the joint and is often used when joining a drawer's front to its sides. The profile of a through dovetail is visible on both adjoining faces and is typically used in case assembly. Each type of joint necessitates its own distinct jig set-up. Of the two, the half-blind dovetail jig is the least expensive to buy or construct, according to Bill Hylton's book "Woodworking With the Router." It's less complicated to use than the through dovetail jig, as you can clamp both pieces of wood to the jig at once and make a single cut for a tight joint.
Manufactured dovetail jigs nearly always consist of a metal base, a clamping system, pressure bars and a comb, or template, for cutting the dovetails. When building your own jig, you can forgo the metal base and use standard 3/4-inch hardwood, according to the book "Shop-Built Jigs & Fixtures." The pressure bars, which hold the work piece to the jig, should be cut from 1 1/2-inch hardwood, while the comb can be made from a piece of 1/4-inch hardwood, or purchased ready-made and attached to an otherwise homemade jig. Many manufactured dovetail jigs have either wing nuts or plastic knobs to clamp wood into place. Hardwood cams provide considerable clamping power to hold your work piece steady.
The jig's comb is what determines a joint's size. Half-inch dovetails are standard, while 1/4-inch dovetails are commonly used on thinner wood or smaller pieces. Some manufactured jigs come with multiple comb templates for greater versatility. Cutting your own dovetail comb from 1/4-inch hardwood can be a time-consuming, tedious process that, according to Hylton, will require you to devote a lot of time to fine-tuning the template to achieve the desired precision. All notches must have perfectly matching widths, and the ends of each tooth must be filed round in a precisely consistent manner. Many hardware stores sell plastic or metal dovetail combs that you can install on a homemade jig.
Don't underestimate the importance of a strong clamping system when putting your jig together. When you cut dovetails, pressure builds up between the work piece, the jig and its clamps. Installing wing nuts over washers on bolts is less expensive and complicated than cutting out cams from hardwood stock, but bolt threads can strip more easily and are harder to tighten and release quickly. Similarly, the jig's pressure bars must be very strong so they don't flex or buckle under pressure. "Shop-Built Jigs & Fixtures" recommends cutting two 1 1/2-inch-by-1 1/2-inch bars of hard maple to length to construct a built-up, extra-strong pressure bar.