Benefits of Sliding Dovetails
A sliding dovetail joint is very similar to tongues and grooves or mortises and tenons. The socket has the same function as a groove or mortise. The dovetail is equivalent to the tenon or tongue.
The mortise-tenon and tongue-groove are always straight-sided. You can use a straight bit to create each. Also, both of these woodworking joints can be stopped (invisible from the outside) or visible joints. Sliding dovetails must be open on one end of the socket. The socket and the dovetail tenon are also cut with the same dovetail bit.
The fit of a dovetail joint is important because of its taper. The best fit provides a little space, the thickness of a dollar bill, between the bottom of the socket and the end of the dovetail, and an equal space between the walls of the joint.
Benefits of a Sliding Dovetail
The dovetail joint excels in tensile strength (pull-apart strength). They work extremely well in cabinet drawers - connecting the sides of a drawer to the front and back. You can use them for doors, legs and rails, and shelves as well.
When you rout a sliding dovetail, you are restricted to the available design of the dovetail bit. Luckily, there are many diameters, lengths and tapers of dovetail bits to choose. Of course, there are limits for large-scale projects like timber-frame joinery or entryway doors, but generally most dovetail bits are adequate.
The conditions for good sliding dovetail joints consist of angle, penetration and any interference. The dovetail's penetration into the socket should be as deep as practical.
You should design dovetail joints so you leave about 25 to 30 percent of the thickness of the socket at each side of the dovetail. This provides a strong joint.
Single dovetails in the ends of drawer sides are easy to design. However, you may need to offset the sockets to provide for greater strength on the back side of drawers. You can offset the socket in the front of the drawer to hide the drawer slides. See Picture:
Dovetail Router Bits
The better dovetail cutters have a carbide outer-layer. When you cut the dovetail socket it requires one pass at full depth. You should consider using a straight bit to pre-plow the socket prior to using the dovetail bit. Otherwise, the dovetail bit may not last as long.
Generally you are likely to use dovetail bits with angles from about 7° to 9° up to 14°. For a given angle, there are different lengths and diameters. It is best to stay away from very narrow-necked dovetail bits. Dovetail bits need at least .2" at the narrowest point, near the shank.
You can purchase commercial dovetail jigs. However, you can make sliding dovetails without spending a lot of money. You can rout the socket on the router table or by hand.
This article deals with routing the socket on a router table.
You set your fence to pre-plow the socket with a router bit that is slightly smaller than the neck of the dovetail bit. Also your depth of cut is shallower than the final depth of the dovetail joint.
Mark your fence for this pre-plow and replace the straight bit with the dovetail bit. Set you dovetail bit to the require depth. When using 3/4" thick piece for the drawer's front and back, I used a 3/8" depth of cut or one-half the thickness.
Since the socket is one router bit wide, there is no danger of a climb cut. You rout the socket with one pass and one setup. This makes the fitting process easier. In addition, you now have a target for making the dovetail tenon. The tenon is the same size as the dovetail router bit.
When you rout the dovetail tenon, you can adjust the router bit height by only 1/64" or you can maintain the same depth. Adjust the fence to take a very small amount on each side of the drawer side's ends. I used a fence then ran the ends on edge past the dovetail router bit. Just turn the board to the other side, and rout the dovetail again. Now the dovetail tenon is forming.
You nudge the fence back and do this procedure again until you have a dovetail tenon that fits the socket. It is a pretty simple procedure.
By making the sockets first and making them only one cutter width, you simplify the process. The goal is to make the dovetail tenon the same size as the dovetail bit.
New - A Video Clip to Demonstrate This Technique!
Dovetail Joint Safety Thoughts
- Be sure and prepare your material accurately before dovetailing. The router table requires square stock.
- The dovetail bit is completely trapped in the work when you make sockets. Square stock and a fence that is square to the tabletop will minimize any risk.
- Use a large board to guide the workpiece along the fence and through the dovetail bit.
- Widening dovetail sockets is hazardous. You may accidentally climb cut and this may pull the stock from your hands. I rout only one dovetail bit diameter - never widen a socket.
Dovetail Joint Assembly Guidelines
- You should pretest the fit of all sliding dovetail joints.
- It is best to apply glue to the top half of the dovetail and the bottom half of the socket. This creates less of a mess.
- Use solid square clamps in the glue-up process.