6. Find the NPD.

7. Find the

8. Find the RPC.

9. Find the lead.

10. Find the change gear.

11. Find the NTCS.

12. Make sure the cutter has the correct DP and

cutter number.

13. Find your corrected chordal addendum and

chordal thickness.

14. Find your corrected whole depth (WD).

15. Determine what kind of material the sample

gear is to be made of.

Now you are ready to machine your gear.

Use the following hints to manufacture a helical

gear:

1. Make all necessary calculations that are needed

to compute the dimensions of the gear.

2. Set up the milling machine attachments for

machining.

3. Select and mount a gear cutter. Use the formula

4. Swivel the milling machine table to the helix

angle for a right-hand helix; face the machine

and push the milling machine table with your

right hand. For a left-hand helix, push the table

with your left hand.

5. Set the milling machine for the proper feeds

and speeds.

6. Mount the change gears. Use the gear train

ratio formula to determine your change gears.

7. Mount the gear blank for machining.

8. Set up the indexing head for the correct number

of divisions.

Bevel gears have a conical shape (fig. 14-12) and

are used to connect intersecting shafts. Figure 14-13,

9. Before cutting the teeth to the proper depth,

view A, shows an example of bevel gears with shafts

double check the setup, the alignment, and all

set at less than 90°. View B shows those set at more than

calculations.

90°. There are several kinds of bevel gear designs. We

10. Now you are ready to cut your gear.

will discuss the straight-tooth design because it is the

most commonly used type in the Navy. The teeth are

11. Remove and deburr the gear.

14-14