Dividing-Head Simple Indexing
Simple (plain) indexing on a 40:1 (or custom) dividing head: crank turns per division = ratio / N, plus the exact full-turns-plus-holes setting for each supplied index-plate hole circle that divides evenly (first-principles ratio arithmetic).
Formula and source
Turns per division = ratio / N (40/N on a standard 40:1 head). For a hole circle of H holes the move is the fractional part x H holes, reported when that product is a whole number.
Simple (plain) indexing on a 40:1 dividing head - first-principles ratio arithmetic as in Machinery's Handbook (Industrial Press), by name; public domain.
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