A: That’s done with what’s called a straight line engine turning machine. The work is called engine turning or guilloche work. Engine turning machines come in two basic flavors. The “round” machines operate like lathes, while the “straight line” machines are more like shapers. The round machines produce concentric circular or oval patterns, and are most familiar as the tools used for pocket watch dials and cases. The classic application looks like a cross-hatched knurled pattern, made of intersecting spirals. In fact, it is made up of concentric circular lines, but the lines have a waviness to them; the intersections of the waves create a pattern that looks like spirals. The machine that does this looks like a lathe headstock, and is hand crank powered, except that the whole headstock and bearing assembly is mounted on springs, allowing it to oscillate from side to side. Some also go forward and back along the axis of rotation.

In addition to the chuck, a series of rosette wheels are mounted to the shaft, the periphery of which rides along a stationary “rubber” piece. That rosette wheel has a wavy or scalloped pattern around the edge, which causes the whole headstock to move from side to side as it rotates, following that pattern as it rubs on the “rubber”. Then, a hand-controlled cutting graver is held on the rotating and oscillating workpiece, and a cut is made that matches the wavy motion of the headstock. The graver is mounted to a fixture equipped with screw feeds with ratchet stops so the cutter can be easily and quickly indexed over a discrete distance from side to side, generating the spacing between cuts.

The Faberge work you’ve seen, though, is mostly done on straight line engines. These have a central chuck to hold the work, which can be indexed to rotary positions as needed (for patterns of radiating lines, for example). The chuck is mounted on a side to side slide, which is itself mounted on a vertically moving slide. A hand crank moves the whole apparatus up and down, while the side to side slide is spring loaded to bear to one side. Again, like the rotary machine, a rubber or follower bar, mounted to the slide, rides up and down against a changeable piece of steel fixed to the machine itself. The edge of that piece has a scalloped or notched or otherwise patterned edge, and as you crank the vertical slide up and down, the sideways slide oscillates from side to side following that scalloped pattern. The pattern piece, by the way, can also be incrementally moved up and down to offset sequential cut patterns. The larger wavy moire’ pattern effect is generated by moving the pattern bar up and down. Meanwhile, with each up and down movement, a hand powered cutter, set into an indexable fixture just like with the “round” machine, is brought to bear on the workpiece, creating the cuts. After each cut, which may be one pass of the cutter, or several passes for deeper work, the cutter fixture is indexed over to one side or the other, as required for the next cut, and if needed, the pattern bar is also offset vertically as might be desired.

Engine turning machines were in use since the 1600’s or so (don’t quote that, I’d have to go look up the exact dates and stuff if anyone really wants, I’ve got it all somewhere) and were very popular as an ornamental effect up through the 1930 or so. Art Deco work used it quite a bit. But the machines are rather labor intensive, compared to the more current “diamond cutting” ornamentation, and require some skill to really master. Plus, the style isn’t so much in fashion any more. Aside from one Swiss manufacturer, who I believe is still custom-making these things (for several tens of thousands of dollars each), they haven’t been made since shortly after World War II, when the English firm, Plante, stopped production. These machines, when available, are quite in demand even so. Much more common in the U.S., are smaller, slightly less versatile machines made by a number of manufacturers, including Hall, and Field. A number of these machines, from the 1920s and 30s are still in daily use at factories like Dunhill, which uses them to decorate cigarette lighters and pens, etc., or at findings manufacturers. A regular item in a number of catalogs, for example, is a little tube or barrel clasp used for neck chains and the like, with a simple engine-turned pattern on the tube.

In my own work, I discovered engine turning machines while in graduate school at Tyler, which had an old Hall machine in good restored condition (It’s since been moved out, in favor of their new CNC mill…(sigh)). Using it first just as a neat way to get really precise scored cuts for folded sheet metal construction, I quickly got interested in the patterns too, especially when I discovered the cool possibilities they open up with reactive metals. So I’ve now got one too, in my back bedroom (converted to workshop). I use it mostly with reactive metals, anodizing niobium to one base color, cutting a loose pattern in it, anodizing to another color in the cuts, and repeating this with several overlaid patterns. I’ve found no other technique which gives me quite the same effect of overlaid glittering colors…And then there’s the “work-efficient” way to decorate a piece of metal, though the results are quite different…I put nice engine turned patterns on a number of pieces of Starret flat ground tool steel stock, and use these for roll printed patterns. You get a pattern of raised lines this way, instead of bright cuts, but it’s still pretty distinctive—and a lot quicker…

For anyone interested in obtaining one of these machines, If you’re handy enough with tools to rebuild an old machine, they are available fairly inexpensively, once you find one. I paid less than a thousand for mine, but it needed extensive work to get it running. If I had it to do again, I might have saved all that work and gone to Gold Machinery in Providence. He’s got quite a number of them sitting around for less than two thousand, ready to run…