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Although the head was moved up and down the column by a simple, quick-action lever-operated rack-and-pinion mechanism, once a coarse setting had been achieved it could then be accurately adjusted into its final position by a very fine feed worm-and-wheel mechanism engaged by a metal-to-metal conical clutch (horizontal axis handwheel); one revolution of the knurled-edge, micrometer-engraved fine-feed handwheel (vertical axis) moved the head assembly through just 1 mm.
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