Engine turning refers to a fine geometric

Geometry

Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....

 pattern that can be inscribed onto metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 as a finish. Aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 is often the metal chosen but any metal can be finely machined to produce intricate repetitive pattern

Pattern

A pattern, from the French patron, is a type of theme of recurring events or objects, sometimes referred to as elements of a set of objects.These elements repeat in a predictable manner...

s that offer reflective interest and fine detail.

Perhaps the most recognizable example of engine turning is the engine cowling (nose) of Charles Lindbergh

Charles Lindbergh

Charles Augustus Lindbergh was an American aviator, author, inventor, explorer, and social activist.Lindbergh, a 25-year-old U.S...

's aircraft, the Spirit of St. Louis

Spirit of St. Louis

The Spirit of St. Louis is the custom-built, single engine, single-seat monoplane that was flown solo by Charles Lindbergh on May 20–21, 1927, on the first non-stop flight from New York to Paris for which Lindbergh won the $25,000 Orteig Prize.Lindbergh took off in the Spirit from Roosevelt...

. In the 1920s and '30s, automobile parts such as valve covers, which are right on top of the engine, were also engine-turned. Similarly, dashboard

Dashboard

A dashboard is a control panel placed in front of the driver of an automobile, housing instrumentation and controls for operation of the vehicle....

s or the instrument panel of the same were often engine-turned. Customizers

Custom car

A custom car is a passenger vehicle that has been modified in either of the following two ways. First, a custom car may be altered to improve its performance, often by altering or replacing the engine and transmission. Second, a custom car may be a personal "styling" statement, making the car look...

 also would decorate their vehicles with engine-turned panels similarly. Recently, one firm engine-turns the faces of its automobile instruments for customizers who don't want to have to turn a panel themselves.

Engravings produced by engine turning are often incorporated into the design of bank notes and other high value documents to make production of forged copies

Counterfeit

To counterfeit means to illegally imitate something. Counterfeit products are often produced with the intent to take advantage of the superior value of the imitated product...

 difficult. The resulting graphics are called guilloché

Guilloché

Guilloché is a decorative engraving technique in which a very precise intricate repetitive pattern or design is mechanically engraved into an underlying material with fine detail...

s.