Page 252 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair
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234 Major Process Equipment Maintenance and Repair
18. Diametral Pitch--The ratio of the number of teeth per inch of
gear pitch diameter.
19. Face of the Gear or Face Width-Width of a gear measured
along an element of a tooth of a spur gear or the width of the pitch
surface measured axially.
20. Flank-The surface of the tooth between the addendum circle and
root fillet.
21. Gear-The larger of two meshing gear elements.
22. Helix Angle--The angle between the tooth on a gear and the axis
of rotation measured at the pitch circle.
23. Lead--The amount a tooth would advance in one complete revolu-
tion along the tooth helix.
24. Lead Modification-The manufacture of a gear with a modified
helix angle to account for the bending and torsional deflection of
the teeth under load.
25. Line of Action-A line drawn tangent to the base circles of a pair
of mating gears. All points of contact between mating teeth lie
somewhere on this line.
26. Mounting Distance- (bevel or hypoid gears) The distance from
the intersection of the two axes of the gears to a locating surface
on one of the gears.
27. Normal--The term applied to dimensions of the tooth made per-
pendicular to the tooth flank.
28. Pinion-The smaller of two meshing gear elements.
29. Pitch-A measure of the spacing and usually the size of a gear
tooth.
30. Pitch Circle-The circle formed in the transverse plane by the
point on each tooth at which the meshing action is purely rolling
with no sliding. The pitch circles of two mating gears are tangent
to each other. It is the base measurement of a gear. A gear size is
the diameter of its pitch circle.
31. Pitch Cone-(bevel gears) The cone with the intersection of the
axes of two mating gears as its apex and the pitch circle of a gear
as its base.
32. Pressure Angle-The angle the line of action makes with a line
drawn perpendicular to the line of gear centers.
33. Spiral Angle-(spiral bevel gears) the angle formed between a
tooth on a gear and the axis of the gear.
34. Thickness of Tmth-The thickness of a gear tooth measured
along the pitch circle.
35. Top Land-The surface of the top of the tooth.
36. Transverse-Measurements made in the plane of rotation of the
tooth.