Recently I was asked about inlaying letters and numbers. While I had seen this on some Pennsylvania furniture, I had never tried it. The closest I had come was inlaying knotted bows on a Seymour card table. What those bows and letters/numbers have in common is that if made from a single thickness of wood, they would be hopelessly fragile, due to short grain. By making them from two layers of veneer with the grain direction of the plys at right angles to each other, the finished inlays are only somewhat fragile.The plys were glued together with hot hide glue, pressing them between warmed boards covered in aluminum foil. The glued together veneer plys are unstable, so it should be restrained by clamping it between boards when not being worked on.
Because of the fragility of the letters/numbers trying to saw the unsupported built up ply would be at best difficult, especially those characters with internal cuts. To improve the stability, the glued up ply is sandwiched between sheets of thin plywood. I use 1/8” luan plywood, which may be difficult to find, but ¼” luan would work just about as well and it seems to be getting thinner all the time, so the difference in thickness isn’t all that great. The stack is nailed around its perimeter with small brads driven into pre drilled holes. The brads are clipped off with diagonal cutting pliers, and peened flush. A print out with the desired characters is glued to the stack. I had a hard time deciding if I should have the grain in the characters, running vertically or horizontally. In the end I went with horizontal so the grain in the characters would run the same direction as the piece into which they inlaid. After viewing the finished inlays I think it may have been better if it would have run vertically. This may not have been an issue with holly and its nearly invisible grain, but with the maple used here or with satinwood, it is something to consider.
Sawing the letters from the stack with a scroll saw.
My variable speed scroll saw is sort of an entry level model, but it does a good job after a few modifications, and the addition of a couple accessories. I discarded the hold down, which did little to aid in the cut. I also fitted an auxiliary table, with a replaceable throat plate to cover the huge throat opening in the factory table. A foot switch allows me to have complete control over the work piece as I start and stop the saw. The last accessory is a magnifying light that facilitates making super accurate cuts.
I used a No. 5 blade; this seemed a good balance between a fine enough blade and one that made an accurate cut. Of course the order of the cuts is important, with the first cuts made being the internal ones. The downside to using the No.5 blade is it can’t turn a very sharp corner, so internal corners should be approached from both sides, instead of trying to “turn” the corner. Outside corners are much easier; you can just pivot in the waste to turn the corner. Even with the thin plywood to stiffen the stack, it becomes quite prone to chatter as the piece nears being sawn free, which requires placing your fingers very close to the blade. This isn’t particularly dangerous because the scroll saw is pretty sedate as saws go, but it robs you of dexterity. The preferred grip is to have a relaxed hold on the stack with your fingers at the edges, where more controlled movements are possible.
Supported by a "birds mouth" the individual characters are refined with needle files.
Despite my best efforts at accurate sawing, the characters as they came from the saw needed some refining, to have smooth, even profiles. As I said before the ply construction makes characters that are only somewhat fragile, so care has to taken not to fracture the pieces as they are being refined. To support the pieces while they are filed, I used a “bird’s mouth” more typically used for fret sawing. It was more comfortable, to have this birds mouth clamped vertically in a vise. A very fine needle file was used for these detailed refinements. Larger outside curves can be refined, by pinching the piece with the fingers and running it against a smooth cut mill file. This method has the advantage of being fast and safer, because the force is in line with the thickness of the inlay, with very little chance of fracturing it.
Scribing around the character with a scalpel, being careful not to over cut at transition points.
With the characters refined, it is now time to inlay them. Positioning of the individual characters is critical for the proper appearance. The most difficult aspect of the whole process is holding the characters in place while scribing around them. I just held them down with my finger being careful not to let them shift or cut myself with the scalpel. Some of the tighter radiuses are best scribed by making a series of light stab cuts, as opposed to trying to draw the knife around the pieces. After a light scribe is done with the characters in place, they are laid aside and a deeper scribe is made to fully define the edges of the inlay. I took extreme care not to over cut at the corners, which will seriously detract from the finished product.
Routing the recess for the character with a Dremel tool fitted with a 3/64" carbide end mill.
The recess is routed with a Dremel tool fitted with a carbide end mill. The size of the end mill is dictated by the narrowest part of the inlay, which in the example shown was 3/64”. The depth setting is critical; there is very little margin for error when working with veneer. When routing the recess, I wore a magnifying visor, which made an accurate cut easy, although, I had to stop frequently to blow the dust away. The end mill can only go so far, so the edges of the recess have to be cleaned up with a scalpel and various gouges.
The recess for the characters are cleaned up to the scribe line with the scalpel and various gouges.
After a test fitting, to be sure they will fit, the inlays are glued in place with hot hide glue. Hide glue is ideal for this, because it will fill the inevitable small gaps without interfering with the finish. I used a veneer hammer to force the inlays into place and then placed the warmed board/aluminum foil combination used before, to keep them in place while the glue sets.
Once they are dry, they can be carefully scraped flush, and finished. The example shown here is maple inlays into cherry. To finish it, I applied lye which darkens the cherry but not the maple. Once dry, some white vinegar was applied, which is supposed to neutralized the lye, but I never had any problems when I skipped this step. What the vinegar does unify the color left by the lye.