Hi Ron/Scott:
This site provides a handy guide concerning the various groove sizes for a variety of formats, including cylinders and diamond discs, as well as 78s, LPs and 45s --
http://www.videointerchange.com/vintage_78s.htm---------------------------------------------------------------------------------------------------
Edison 80-RPM Diamond Discs -- 3.7 mil spherical or non-truncated conical stylus
Edison White Wax, Brown Wax, Concert, and Gold Molded -- 7.4 mil Spherical stylus.
Edison Blue Amberol Cylinders -- 3.7 to 4.2 mil non-truncated spherical stylus
Edison Wax Amberol Cylinders -- 4.2 mil spherical stylus.
Wide Groove Acoustical 78 RPM Lateral Discs -- 3.8 mil truncated elliptical stylus
Pre-1935 Lateral Cut Electrical 78's -- 3.3 mil truncated elliptical stylus.
1940's -+Transcription Recordings -- 2.3 mil truncated elliptical stylus.
Early LP's -- 1.5 mil truncated elliptical stylus
Modern Micro-groove LP's -- 0.7 mil elliptical stylus
Standard Groove 78 RPM Discs -- 3.0 mil truncated elliptical stylus
Narrow Groove 78's such as Polydor -- 2.4 mil truncated elliptical stylus.
Late 1930's Lateral 78 RPM Discs -- 2.8 mil truncated elliptical stylus
Aluminum Instantaneous discs -- 6.0 mil conical
1931 to 1935 RCA Pre-Grooved Home Recordings -- 5.0 mil spherical stylus
Pathe´ 78's -- 3.7 mil truncated conical stylus
Etched Label Pathe´ to 14 inches in diameter -- 8.0 mil conical
Etched Label Pathe´ over 14 inches in diameter -- 16 mil conical
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Joe