Page 253 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Power Transmission Gears 235

37. Width of Space- The tooth space width measured along the pitch
circle.
38. Working Depth- The radial distance $+-om the addendum circle
to the working depth circle. The depth of engagement of two mat-
ing gears.
39. Working Depth Circle-The imaginary circle on a gear formed
by the deepest points of the tips of the mating gear teeth as the
gears pass through mesh.

How Gears Work
Figure 6-10 is a cross section of a pair of gears in mesh. This cross
section is in the transverse plane (plane of rotation) and applies to spur,
helical, or spiral bevel gears. All contact is along the line of action,
which is the heavy broken line. Note that the pressure angle, which is
often referred to on gears, is measured between a perpendicular to the
line of centers and the line of action. All contact will be on the line of
action normal (perpendicular) to the tooth profile; it commences at point
“A” and is completed at point “B.” The relationship between the length
of the line of action and the base pitch is referred to as the transverse

Figure 6-10. Transverse section through a gear and pinion in mesh.