What is engine turning - CRATEX Abrasives

Engine turning is a process of adding fine (decorative) patterns on a flat metal or steel surface as a finish. It brings a truly unique touch to a workpiece and gives it an almost holographic depth. And it’s not just for being pretty, it is also thought to make cleaning easier. Aluminum is the metal that is used most often, but, basically, any metal can be decorated with these repetitive, swirly patterns - stainless steel, nickel, gold, chrome, etc.

Traditionally, the term in English was used in jewelry and horological trade. In Francophone regions the synonym for engine turning is guilloche, patterned curved-line finish produced by the application of a single-point cutting tool (rose-engine, straight-line engine or decoration lathe).  It is usually seen on fine, high-end horological work and exquisite jewelry design (e.g. contemporary watch engraving dominated by the Swiss, or the delicate work of Fabergé under the Russian Tsars).

Jeweling

Fine jewelers don’t like referring to engine turning as “jeweling”, since they consider the process too coarse for an Ornamental Turning that they deal with. Besides, guilloche patterns are patterned designs found on money, stock certificates and other valuable papers, with the main purpose to make counterfeit more difficult.

Spotting

On the other hand, “spotting” was the term used for an abrasive finishing process. A rotating disc or a rotating dowel with an abrasive at the bottom would be pressed down to a metal surface, to create fine, overlapping swirls as the finish. “Spotting” became very popular at the beginning of the 20^th century, and the most recognizable example is the decoration on the engine cowling (nose) of Charles Lindbergh's aircraft, which was a custom-built, single-seat monoplane, that took him on the first direct transatlantic flight from Long Island (NY) to Paris (FRA).

Later, during the 20s and 30s, people started decorating car parts like valve covers, instrument panels, and other engine-turned panels that were added as a part of customization. By the middle of the 20^th century, engine turning has nearly disappeared as an industrial process, and the term “engine turning” began to be applied to “spotting”, mostly among automobile enthusiasts, so “engine turning” quickly became the new and legitimate term for decorative swirls created by pressing down abrasive sticks among automobile restoration community.

There are a few other terms often used interchangeably with “engine turning”, such as damascening, krayling, ornamental turning, swirling, snailing, mottling, however, there are limitations in appropriateness when it comes to applying it to different processes and work pieces. For example, the term “damascene” has been used in the jewelry and ornamental metalwork trade since the 16^th century. Although we find the term “damascene” used for an abrasive finish since the 40s, “damascening” refers primarily to a two-metal finish, a process of inlaying two precious-metal wires into one another to produce intricate patterns, which is completely different from both “engine turning” and “spotting”. Besides that, there’s also the Damascus steel, which is something completely different. The term is used to describe a very specific “wavy” patterned sword blades that appeared in the West through trade from Damascus. The process of creating the wavy pattern includes a tool that this a shoulder brace and an angled, polished end.

So, each of the “synonyms” for engine turning should not be used ever so lightly. When it comes to putting an abrasive finish to a metal surface, although nowadays “engine turning” is often used interchangeably with “jewelling”, the term “engine turning” is primarily used for high-quality automotive metalworking – the ornamentation of classic cars and hot rods that creates a classic look of old-school craftsmanship (e.g. steering wheel decorations, valve cover, firewall, dash and console, glovebox, rear spring covers, switch panels, gas tank straps – you name it!) or motorcycles (e.g. gear case, instrument pod, tank, headlight, etc.) “Jeweling” refers more to the decorative touch on the different parts of firearms and knives, tools, instruments, and so on – all objects that can be made prettier and shinier, really. This is why we’ll discuss jeweling in a separate article, so make sure you check it out here.