Don't Let Bad Dovetails Happen to You
Dovetail joints are one of the hallmarks of quality woodworking, and a router and store-bought jig make quick work of them. But the fit of these eye-catching corners must be precise, as shown below. And if you don't use your jig often, it's easy to forget even one small thing that results in poor-fitting joints. Here's how to minimize the headaches.
These hints will get you started on the right foot
* Read the owner's manual and do what it says. Proper setup heads off most goofs, and when you need help, the solution often will be found there.
* Use the correct router bits, guide bushings, and jig templates. Manufacturers design all three elements to work together; straying from the right combination invites problems.
* Machine all your workpieces square and to the correct dimensions. Interlocking pieces don't have to be of the same thickness, but they must be flat and square to make a tight-fitting joint. When you're routing multiple joints with the same setup, make all common pieces (drawer sides, for example) identical in thickness and width.
* Always make test cuts in scrap stock that's of equal dimensions to your workpieces until you achieve the desired fit. Don't mess up your project parts trying to dial-in a joint.
* Slow your router bit speed to avoid burning the pins and tails. Particularly when routing closed cuts, such as half-blind pin sockets, at higher speeds, trapped heat can build up and burn the wood; and burned surfaces don't bond well with glue.
* Save the final test pieces to use as set-up blocks for the next time. Then use those to set the bit depth and workpiece position in the jig.
Head off half-blind errors
GOOF: You've cut tails instead of pins on a drawer front.
HOW TO AVOID IT: Before routing, label all components (front, sides, back) near the joint for easy reference. Also, whenever possible use contrasting stock for your drawer front so it stands out from the other parts.
GOOF: Thin or unequal end tails or pins weaken a joint or leave it with an unattractive appearance, below.
HOW TO AVOID IT: If your jig allows variable pin spacing, set the template fingers so you get at least a half-pin on each end, as shown below. If your jig does not have variable spacing, you'll need to plan your project or drawer widths to match the template spacing. To do this, measure the template width between half-pins closest to what you'd like, as shown below, and make that your workpiece width.
Thwart mistakes with through dovetails
GOOF: You've cut your tails and pins with the wrong bit or the wrong side of the template, as shown below.
HOW TO AVOID IT: Remember this: Dovetail bits use straight template fingers, and straight bits use angled fingers. Again, labeling project parts helps avoid confusion. Also, sketch the joint on the end grain and mark an X to indicate the areas to remove.
GOOF: The bit tears chunks from your workpiece as it exits the cut, below.
HOW TO AVOID IT: Sandwich your workpiece in the jig between two backer boards, as shown below. Like a zero-clearance insert on your tablesaw, these sacrificial boards support the fibers of your workpiece to prevent tear-out. When routing pins or tails wider than the bit diameter, rout in incremental steps, removing the waste material in three or four left-to-right passes rather than simply plunging through the workpiece.