Diamond Banding

A common router bit and simple jig yield a jewel of an inlay piece.

By Rob Millard
Pages: 34-37

From the October 2011 issue #192
Buy this issue now

I’m in awe of the cleverness of period woodworkers. Working with simple tools, they created objects of art that have stood the test of time. Of particular interest to me are the inlay bandings produced during the Federal period (1775-1815).

At first glance they would seem an impossible task, even with today’s tools. Yet for the most part they are simple laminations sliced at various angles which are then glued in a pattern between sheets of veneer. When I first examined photos of diamond bandings, I assumed they were made by cutting a three-layer stack of contrasting wood  on a diagonal and gluing them back together between veneers. This is how modern diamond bandings are made. But period bandings often have what can be best described as a horizontal pattern shift.

Just as it should be: A simple, precise, and effective jig helps you produce perfect work.

This shifting results in the top and bottom points of each diamond not aligning vertically. I couldn’t see how this misalignment would occur with segments cut from a stack. Then I saw an original banding in person – which raised more questions than it answered because the grain ran horizontally through the banding, rather than on the diagonal as I had assumed.

The only thing that was clear was how the misalignment could occur, because even the slightest variation in the size of the components would cause the pattern to shift. Period cabinetmakers were masters, but cutting small, delicate diamonds and triangles with the precision required, and in a timely manner, seemed a tall order. Then it occurred to me that the key was to cut the contrasting woods at the same time, ensuring precise alignment.

Indexing: Spacing the V-grooves is critical and the index mark makes for foolproof accuracy.

With a router this would be easy, but I wanted to be sure it was possible with hand tools. So to test the theory I made a crude plane with a V-shaped iron and a jig to guide the plane. The banding proved surprisingly simple (if not quick) to make with hand tools.

Using a router greatly increases the speed at which you can make the banding, and (to a degree) the accuracy of the finished product. I was actually concerned the router would be too precise, and the resulting banding would lose the handmade variations crucial for a period look. In the end, this was an unfounded concern, because even with a carefully made jig and well-prepared stock, considerable potential for “errors” exists.

Accuracy is Essential
This banding begins where all projects begin, with the stock preparation. The banding is easy to make if every step is done with great precision. Errors tend to be cumulative, so starting with stock that is accurately milled is essential.

The pattern emerges: The router and jig work together to produce astonishingly accurate grooves.

This particular banding starts with two strips of holly and one of ebony that are milled to 1⁄4″ x 2″ x 37″. The dimensions aren’t critical, but uniformity is. Flatten the strips with a handplane, using a straightedge and winding sticks to check for accuracy. With one face flat, run the strips through the planer.

Be sure your planer knives are adjusted so they are absolutely parallel to the bed – otherwise the strips won’t have the necessary accuracy. The edges of the strips also need to be parallel with a high degree of accuracy. To assist in checking setups, also make a strip of scrap wood using the same settings.

Edge-glue one strip of holly and the ebony together. I did this with the strips lying on the bench to aid in getting the faces flush. Handscrews provide the clamping pressure, which is more than enough because the joint isn’t structural. Use plastic food wrap to keep the strips from adhering to the bench.

Closing the book: Sawn apart and folded together, the banding starts to take shape.

Jig Details
At the heart of making the banding is a jig that guides the router and properly spaces the V-grooves. The jig has a bed of 3⁄4″ hardwood plywood. A cleat underneath it allows the jig to be secured in a vise and provides a place to clamp the strips while routing. Glue and nail two guides of the same thickness as your strips to the bed with 41⁄2″ between them. At an exact 90˚ to the guide strips you’ll need two guides that  are spaced to allow the router base to glide effortlessly between them, but without play (wax helps). The accuracy of the router guides is critical to the proper outcome of the finished banding. Because of the way the strips will be arranged, any deviation from true will be doubled, making a successful banding all but impossible.

To provide clearance for the strips, place pieces of veneer under the router guides. Like the guide strips, the router guides and veneer are glued and pinned in place. This banding is made with a 120˚ router bit. Set up the router with the bit so it projects about 1⁄64″ shy of half the thickness of the strips.

First make a test cut in your scrap from both sides, adjusting as necessary to set the depth. Complicating this set-up is the fact that the bit leaves a small flat at the bottom of the V-groove, which means that routing halfway through the strip would make the V too deep.

Keep it square: The peaks of the ebony, must be square to the edge before the second set of V-grooves are made.

Setting the spacing of the V- grooves involves a bit of trial and error, too. The V-cut in the jig will aid in setting the spacing. Moving the test strip over until the edge of the V intersects with the edge of the V in the jig will result in the proper spacing, but make a few test cuts to be sure. The goal is to have the peaks of the Vs in the strips come to a sharp point without reducing the thickness of the strips. To confirm that the peaks come to a sharp point, put a straightedge across the top – that will reveal any gaps. Once you get the spacing correct, make an index mark on the inside face of the guide strip. This mark will set the spacing by placing it in the bottom center of the previously cut V.

Clamp the strips firmly as the cuts are made, with the clamps as close as possible to the cut. Holly burns easily, so watch your feed speed to prevent this. The cutting goes rather quickly, taking a little over an hour to complete the 37″ strip.

When you near the end of the strips, you’ll have to move the clamps to the already routed section. To prevent deforming the peaks of the V, pad the clamps with soft scrap wood. When you are done routing, remove the flat left at the bottom of each V with a V-gouge. (I’ve found that the angle of the V-gouge does not need to match the angle of the groove, it is only important to remove the flat.)