Guilloché (or Guilloche) 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. Specifically, it involves a technique of engine turning, called guilloché in French after the French engineer “Guillot”, who invented a machine “that could scratch fine patterns and designs on metallic surfaces”. The machine, called a rose engine, improved upon the more time-consuming practice of making similar designs by hand, allowing for greater delicacy, precision, and closeness of the line, as well as greater speed.
Another account gives the credit of inventing this method to Hans Schwanhardt (- 1621) and the spreading of it, to his son-in-law Jacob Heppner (1645).
A guilloche is a repetitive architectural pattern used in classical Greece and Rome, and neo-classical architecture as well as medieval Cosmatesque stone inlay work, of two ribbons winding around a series of regular central points. These central points are often blank, but may contain a figure, such as a rose. Guilloche is a back-formation from guilloché, so called because the architectural motif resembles the designs produced by Guilloche techniques.
Engine turning machines manufactured in the traditional fashion with cast iron and heavy wood bases and precision scraped machined surfaces have been made up to ca 1967 (e.g. Neuweiler und Engelsberger). Individuals continue the craft of making these elegant machines but they are in very limited quantities.
A Guilloche Machine was granted a US Patent in 1968 by Wilhelm Brandstatter. The original assignor was a firm called Maschinenfabrik Michael Kampf KG. A photo of this machine can be seen at Turati Lombardi's history page.
In the 1920s and '30s, automobile parts such as valve covers, which are right on top of the engine, were also engine-turned. Similarly, dashboards or the instrument panel of the same were often engine-turned. Customizers also would decorate their vehicles with engine-turning panels similarly.
Guilloche describes a narrow instance of guilloche: a design, frequently architectural, using two curved bands that interlace in a pattern around a central space. Some dictionaries give only this definition of guilloche, although others include the broader meaning associated with guilloché as a second meaning. Note that in the original sense, even a straight line can be guilloché, and persons using the French spelling and pronunciation generally intend the broader, original meaning. Translucent enamel was applied over guilloché metal by Peter Carl Fabergé on the Faberge eggs and other pieces from the 1880s.
In today’s terminology 
In consequence of the nature of the design, which is usually a series of lines that are, or look very much like they are interwoven into one another, any design engraved on metal, printed, or otherwise erected on surfaces such as wood or stone, that go in a similar style of constant wriggling that interlock - or look like they are interlocking - with one another, is referred to as guilloché.
Some of the more common ones are the following:
- Engraved (in metal, mainly sterling): in fine timepieces (mainly pocket watches), fine pens, jewelry charms, snuffboxes, hair-styling accessories, wine goblets etc. Examples of famous works of Guilloché are the engravings on Faberge eggs.
- Erected: on stone for architecture, in wood for styling, on furniture or molding, etc.
- Printed: on bank notes, currency or certificates, etc., to protect against forged copies. The pattern used in this instance is called a spirograph in mathematics, that is, a hypotrochoid generated by a fixed point on a circle rolling inside a fixed circle. It has parametric equations. These patterns bear a strong resemblance to the designs produced on the Spirograph, a children's toy.
Other names for Guilloché 
The engine turning machine characteristic of Guilloché is called by other names in specific uses:
- Rose engine (metalwork)
- straight line engine turning Tour à guilloché (metalwork)
- Holtzapffel lathe, named after the founder of an ornamental lathe manufacturer John Jacob Holtzapffel
- Decoration lathe (metalwork)
- damaskeening (watch movements and horology)
- Geometric lathe (security printing)
- Cycloidal engines (security printing)
- Ornamental turning or ornamental lathe (woodcarving).
The different types of the machines refer to different models and different times during the development of the engine-turning machine.
See also 
- What kind of a machine did Faberge' use to engrave the gold under the enamel on his famous eggs and other irregular shapes? by Peter Rowe.
- Guilloché Enameled Luxuries: Engraved memories of a fanciful era, Professional Jeweler Archive, March 2001.
- Argent Blue pens
- GUILLOCHE MACHINE US Patent No. 3,406,454
- Photo of Guilloche Machine
- The Century Dictionary: An Encyclopedic Lexicon of the English Language By William Dwight Whitney 1889
- Roman Pavements by Henry Colley March 1906
- The Anglo-Saxon Review By Lady Randolph Spencer Churchill 1901.
- eBay Guides - The Guilloché Enamelling Process and Charm Collecting