MILLING MACHINE OPERATIONS - OD1644 - LESSON 1/TASK 1
FIGURE 11.
INDEX PLATE AND SECTOR.
First side- 24, 25, 28, 30, 34, 37, 38, 39, 41, 42, 43 holes.
Second side- 46, 47, 49, 51,53, 54, 57, 58, 59, 62, 66 holes.
(5)
Indexing Operation.
The two following examples show how the index
plate is used to obtain any desired part of a whole spindle turn by plain
(a)
To Mill a Hexagon.
Using the rule given in paragraph 4c(3)(b)
above, divide 40 by 6, which equals 6 2/3 turns, or six full turns plus 2/3
of a turn on any circle whose number of holes is divisible by 3. Therefore,
six full turns of the crank plus 12 spaces on an 18-hole circle, or six full
turns plus 26 spaces on a 39-hole circle will produce the desired rotation
of the workpiece.
(b)
To Cut a Gear of 42 Teeth. Using the rule again, divide 40 by 42
which equals 40/42 or 20/21 turns, 40 spaces on a 42-hole circle or 20
spaces on a 21-hole circle. To use the rule given, select a circle having a
number of holes divisible by the required fraction of a turn reduced to its
lowest terms.
The number of spaces between the holes gives the desired
fractional part of the whole
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