Precious Stones for Cutting Precious Records

There is a long history of use of precious stones as industrial materials, from precision bearings to cutting tools, lapping compounds to grinding tools and several other specialised applications.

The recording of phonograph records is essentially a machining operation, performed by means of a machine tool called a disk recording lathe. A special cutting tool is used to cut a continuous spiral groove on the surface of a blank disk. This tool is called a disk recording stylus, or simply cutting stylus.
The big difference to other forms of machining is that there is sonic information stored as modulation of the cut groove, which can be reproduced on another special machine, often called turntable or record player, or disk reproduction system.

Many different stylus materials and geometries have been used through the years, along with different blank recording disk materials. The superiority of precious stones as cutting stylii was already evident from the early days of disk recording, so they are now the only type of stylus used for cutting masters for vinyl record manufacturing.

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Lab Report: Making cutting stylus shank adapters

Stereophonic cutter heads developed by Neumann are designed to accept a cutting stylus with a conical shank, resembling a micro-miniature version of a Morse Taper, a type of fitting frequently encountered in machine tools, especially metalworking lathes. Vinylium and FloKaSon cutter heads also adopted the same fitting for the sake of compatibility. But most other cutter heads, especially all those predating the stereophonic era, used long, thin cylindrical shanks, often with a flat machined on one side, to allow a set-screw to align the stylus and secure it in place.

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