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.
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