Joinery Class: Half-Blind Dovetails

Master a classic joint using a combination of power and hand tool techniques

Considering that examples of dovetail joinery can be traced back to ancient Egyptian times, it’s fair to say that woodworkers have been arguing about the best way to cut dovetails for thousands of years.

Today’s version of this debate often boils down to whether or not the “best” dovetails are cut by hand or machine. My hybrid approach for making half-blind dovetail joints is a good compromise. (I use a similar technique to make through dovetails; see Work Smarter With A Standing Desk)

Half-blind dovetails are most commonly used to join drawer sides to drawer fronts. The drawer I’m building here has a 7⁄8"-thick cherry front and 1⁄2"-thick poplar sides. A thick drawer front like this allows for longer tails, which I find more attractive.

The “machine” part of my technique involves cutting tails on  the tablesaw and removing waste between pins on the drawer front using a dovetail bit in the router. The angle of your dovetail bit (I use a 14° bit most frequently) dictates the required tilt of the tablesaw blade when making tail cuts. For best results, have a dedicated saw blade custom ground so the blade leaves a flat-topped kerf when tilted for tail cuts. If your local sharpening service can’t modify a ripping blade for you, contact Forrest (www.forrestblades.com) to have a dovetailing blade prepared.

One final consideration is worth mentioning: Planing the sides of a finished drawer to fit its opening is best done from front to back. So make sure the grain of each side runs uphill toward the back of the drawer for smoother planing.

Put your marking gauge & dividers to work

I like to avoid math whenever possible. I also believe in the longstanding advice that you should never measure if you can simply mark. This dovetail layout method complies with both preferences.

Begin by setting the marking gauge to the planned tail length (5⁄8") and scribing baselines on the pin and tail boards. Remember that there’s also a baseline for the sockets, scribed along the inside face of the drawer front and equal in depth to the thickness of your tail board.

When you finish with the marking gauge, reach for your dividers. The divider layout method (explained at right) enables you to easily divide a tail board into symmetrically spaced, identically sized dovetails.

If the tail-pin proportions aren’t to your liking after going through the procedure, simply adjust your dividers narrower or wider and repeat the process until the spacing is right.

Divider layout in 4 steps

1. Mark 1⁄4" in from the outside edges of the tail board, and adjust dividers slightly larger than desired tail width.
2. Identify left edges of tails by “walking” dividers across width of tail board, starting 1⁄8" from edge. After 3 steps, divider point should land on opposite 1⁄4" mark. Adjust dividers and repeat if necessary.
3. Identify right edges of tails by walking dividers back in opposite direction.
4. Use square and bevel gauge to mark dovetail layout along top edge and down to baselines on tail board.

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See Chris Hedges demonstrate his divider layout method in this video:

 

A dedicated sled ensures precision and speed when making tail cuts

Whether I’m making through or half-blind dovetails, I cut the tail cheeks on my tablesaw, using a sled that slides in both miter gauge slots. Since I plan to rout the pins with a 14° dovetail bit, I have a ripping blade custom-ground so that the blade leaves a flat-topped kerf when tilted to 14°. Blade-sharpening services are usually able to modify an existing ripping blade in this way.

Once the blade is tilted and raised to the proper level in the jig, the adjustable stop in the jig’s fence allows me to make matched cuts in both drawer sides, as well as symmetrical cuts, by rotating the workpiece 180°.

Set the angle. After you lay out the tails, bring the bevel gauge to your tablesaw to set the blade angle.

Precise cheek cuts. Designed for cutting dovetails, this jig has an adjustable stop that guarantees precision when making symmetrical and repeat cuts.

Waste removal. A scrollsaw makes quick work of removing waste between tails, but a coping saw will also do the job.

Rout out the pinboard tail sockets, then pare to the line

This step begins and ends with hand tools. In between, you rout to save time. I clamp the drawer front securely to the edge of my workbench with the end facing up to receive the layout. With the tails aligned over the end and held firmly in place, I use a marking knife and square to scribe the pin outlines and then extend them down the inside face of the drawer front to the baseline. To rout the tail socket waste inside my layout lines, I rely on a tail board stopblock that’s clamped at a right angle across my pin board (photo below). Position the stopblock to stop the router base when your dovetail bit is 1⁄16" shy of the socket baseline. It’s still necessary to guide the cut freehand as you move the router side to side. To do this, you’ll need to grip the router firmly and sight through openings in your router base.

From tails to pins. Hold the tail board firmly in place and transfer the tail cheek layout with a marking knife.

Pare to the line. A little more cleanup with a chisel and you’re ready for assembly.

Test, adjust, assemble & shave the joint smooth

Expect to do some test-fitting and fine-tuning before you finally glue each joint together. I like the pin board to stand slightly proud of the tail board when a half-blind dovetail joint goes together. This enables me to plane the corner smooth and flush with just a few strokes.

Passing the test. After some final paring, this fit shows the joint is ready for glueup.

Plane it flush. A slightly proud drawer front invites planing to make the joint smooth and flush.