Simple indexing uses a worm gear attached to a crank to rotate a dividing head spindle in precise increments. Turning the crank one full rotation rotates the spindle 1/40th of a full turn due to the 40 tooth worm wheel. To calculate the number of crank turns needed for a given number of divisions, divide 40 by the number of divisions, with examples given of dividing 40 by 8 and 7 to get the turns required to cut 8 and 7 flutes, respectively.

1. 1
Simple Indexing
• Work positioned by means of crank,
index plate, and sector arms
• Worm attached to crank must be
engaged with worm wheel on dividing
head spindle
• 40 teeth on worm wheel
• One complete turn on index crank cause
spindle and work to rotate one-fortieth of a
turn (ratio of 40:1)

2. 2
Simple Indexing
• Calculating the indexing or number of
turns of crank for most divisions, simply
divide 40 by number of divisions to be
cut or,
40
Indexing =
N

3. 3
Simple Indexing
• The indexing required to cut eight flutes:
crankindexofturnsfull5
8
40
=
• The indexing required to cut seven flutes:
crankindexofturns
7
5
5
7
40
=
The five-sevenths turn involves use of
an index plate and sector arms.