History of the screw cutting lathes and how Edison's phonograph fits into the history. 

The history of screw cutting lathes shows how early versions had the lead-screw on the same shaft as the workpiece so that a thread could be copied from the lead-screw to the workpiece. If a different thread was required, the lead-screw was changed. It was only later that the gear train was introduced to allow many pitches to be produced using a single lead-screw. Edison's phonograph went through the same stages of development.
REFERENCES:
Where DO Screws come from?
• Where DO screws come f...
Understanding gear trains
• Understanding Gear Tra...
Understanding Metric Imperial Conversion Gears for Engineer's Metal Lathes:
• Metric Imperial Conver...
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