Making Cove and Pin Joint DIY

The cove and pin joint is a real eye catcher. It has a beautiful symmetry, is captivatingly intricate, and adds a special I quality to any project. It is also a nice way of combining careful machine work with some pleasurable hand fitting.

I first became fascinated with the joint after seeing it on a box by Timothy McClellan of Minneapolis, Minn, in the first Biennial Design Book (Taunton Press, 1977). I later saw the joint on drawers in several older case pieces, but those joints were cut by machines that are no longer available.

How I worked on pin and cove joint

Eventually, I worked out a hand/machine method for cutting the joint with a modified plug cutter chucked in my drill press. For the maximum visual effect on things like drawers or jewelry boxes, I cut the pins in a dark wood and the coves in a light wood.

My method for cutting the joint is to mill the pins by running the plug cutter into the end grain of one board, and then use the same cutter to score the face of the mating piece to mark out the coves. Then, I bore out the pin holes and trim the outside of the cove with a saw, chisel, and knife.

Before you can cut the joint, you'll have to modify a four-fluted plug cutter to form pins and coves, as shown in figure 1 detail regrind a bevel-edge gouge that matches the outside diameter of the coves, and build an indexing jig for your drill press.

My cutter is a stock Fuller model designed to cut this plugs. The outside diameter of the cutter, which is used to mark out the coves, is about % in. The odd-looking & in. gouge with its edges ground back is used to trim the rough’s awn coves. A standard 2%-in.-dia. twist drill clears the pin holes.

Working on Indexing Jig

My indexing jig is based on a 10-in.-square piece of e-in. aluminum plate that has %-in, holes drilled on ar-in. centers along one side, as shown in the drawing. The joint components are clamped to an L-shaped wood tray that slides along the indexing plate. To ensure that mating pieces will interlock, I use the same jig for both the end grain pins and the face coves, so any inaccuracies are mirrored on each piece and cancel each other out.

No matter how good your setup, though, you'll still have to invest a healthy amount of time and patience to hand fit the pieces together. I average about five minutes per pin for hand fitting,

To make the jig. I lay out the hole locations with a 6-in. steel rule and a sharp knife, then make a punch mark to guide the drill into the aluminum. The spacing isn't terribly critical here: small variations won't show and will be duplicated on both pieces.

Bore two holes’ process

Next, bore two holes so that you can fasten the plate to the slots on your drilling press table with flat head machine screws, washers and wing nuts. You should have enough free play in the slots to adjust the jig back and forth. Make sure the side with the step ping holes hangs just over the table edge to give clearance for the sliding tray, I made the pin by spinning in. dia. brass rod in the drill press chuck and sanding until it fits.

Last but not the least

The sliding tray is two 9 in. by 7 in. pieces of hardwood or particleboard glued together at right angles along the 7 in. side. The tray slides along the edge of the index plate, hanging over the side with the holes. It's butted against the metal edge and the index pin each time the pin is moved to locate a new cut. To cut the pins, clamp the dark wood end grain up on the vertical portion of the tray.

The coves are cut with the pieces aligned in the same position at the corner of the tray, but this time along its horizontal surface. And thus you start starting on cove and pin joint.