**PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2**

FIGURE 49.

PROTRACTOR VERNIER SCALE READINGS.

(3) *Use and Application. * The bevel protractor is used to measure the

angular clearance on a ring gear (figure 50, view A, on the following page).

The bevel protractor can be used to establish an angle and determine its

relationship to other surfaces as shown in figure 50, view B.

The acute

angle attachment is connected to the slotted extension of the dial and is

used to accurately measure acute angles as shown in figure 50, view C.

m.

*Gear Tooth Vernier Caliper.*

(1) A gear tooth vernier (figure 51, views A and B, on page 80) is

used to measure the chordal thickness of a gear tooth on the pitch circle

and the distance from the top of the tooth to the pitch chord (chordal

addendum) at the same time. The vernier scale on this tool is read in the

same way as other verniers, except that graduations on the main scale are

0.020 inch apart instead of 0.025 of an inch.

**78**