Fig. 10
one idler D. The idler D
serves to rotate the index
plate in the same direction
as the crank, thus in making
280 turns of the crank, nine
divisions are lost, giving the
correct number of divisions,
271. The sector should be set
to indicate 17 turns, or 3 holes
in the 21 hole circle, and the
head is ready for 271 divisions,
the indexing being made the
same as for plain indexing.
Head Geared for 319 Divisions.
Fig. 10 shows the spiral head geared, compound gearing, for 319 divisions. Referring to the table on page 217, the gears called for are: C, 48 teeth; F, 64 teeth; G, 24 teeth; E, 72 teeth and one idler D, 24 teeth. The sector should be set to 429 turns, or 4 holes in the 29 circle; the head is then ready for 319 divisions.
Spacing for Quarter Degrees.
Example 3.
- Required H, n and x for spacing 14 degrees, or 1440 divisions.
- Assume H = 33, n = l.
- Then
- One idler is required.
The following table gives data required for spacing 14° and 16°. For fractional parts of degrees obtainable by plain indexing see page 54.
Divisions | Index Circle |
No. of Turns of Index |
Gradua- tion |
Gear on Worm |
No. 1 Hole | Gear on Spindle |
Idlers | ||
1st Gear on Stud |
2d Gear on Stud |
No. 1 Hole |
No. 2 Hole | ||||||
16° 14° |
49 33 |
149 133 |
28 44 |
64 64 |
56 40 |
100 100 |
24 24 |