Page 251 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Power Trammission Gears 233

Figure 6-9. Gear tooth nomenclature (transverse plane).

9. Bottom Land-Surface of the bottom of the tooth space.
10. Chordal Addendum--The distance from the outside diameter to
the point where chordal thickness is measured on the pitch circle.
11. Chordal Thickness-The straight line thickness of the gear tooth
measured on any circle. Usually measured on the pitch circle un-
less orherwise stated.
12. Circular Pitch-The distance measured along the pitch circle
from a point on one tooth to the corresponding point on an adja-
cent tooth.
13. Clearance--The radial distance between the working depth circle
and the root circle. Also, the distance by which the tip of the tooth
of a particular gear will clear the bottom land of the mating gear.
14. Cone DiStance-(beveZ gears) The distance along the pitch cone
from the apex to any given point on the tooth.
15. Contact Ratio-The ratio of the length of the line of action to the
base pitch.
16. Dedendmn-lk radial distance from the pitch circle to the root
circle or to the root diameter,
17. Dedendum or Root Circle--The circle that bounds the bottom of
the teeth. Usually referred to as root diameter.