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Defining a gear for manufacturing, or procurement
requires engineering and manufacturing information. Typically,
this information is provided on a engineering drawing. The
dimensional requirements of the gear may be expressed as a
mechanical detail drawing dimensional data or specified by use a requirements
chart on a mechanical drawing.
The following is a typical gear manufacturing
requirements chart for Spur and Helical gears.
|
Spur Gear |
Description
(See Below) |
Nomenclature |
| A |
Number of Teeth |
| B |
Diametral pitch or module |
| C |
Pressure angle |
| E |
Standard Pitch Diameter |
| F |
Tooth Form |
| G |
Max. Calc. Circular Thickness on Std. Pitch Circle |
| K |
Maximum Tooth to Tooth Total Error |
| L |
Specification Master |
| M |
Outside Diameter |
| J |
Maximum Total Error |
| H |
AGMA Quality / Tolerance Class |
|
Helical Gear |
|
Description
(See Below)
|
Nomenclature
|
| A |
Number of Teeth |
| B1 |
Normal Diametral Pitch or Module |
| C1 |
Normal Pressure Angle |
| D |
Helix angle |
| D1 |
Hand of Helix (Right or Left) |
| E |
Standard Pitch Diameter |
| F |
Tooth form |
| G1 |
Max. Calc. Normal Circular Thickness on Standard Pitch
Circle |
| J |
Maximum Total Error |
| K |
Maximum Tooth to Tooth Total Error |
| L |
Master Specification |
| M |
Outside Diameter |
| H |
AGMA Quality / Tolerance Class |
Description:
A. Number of Teeth: Total number of teeth on
gear.
B. Diametral Pitch: Ratio of the number
of teeth on the gear to the number of inches in the standard
pitch diameter.
B1) Transverse Diametral Pitch:
Diametral
pitch in the transverse plane.
C) Pressure Angle: Angle between the
gear tooth profile and a radial line at the pitch point.
C1) Normal Pressure Angle: Pressure
angle in the normal plane.
D) Helix Angle: Angle between the
pitch helix and an element of the pitch cylinder, or any
specified feature.
D1) Hand of Helix: Direction in which the
teeth twist along the axis. (right hand twists clockwise, and left hand
twists counterclockwise).
E) Standard Pitch Diameter: Diameter of
the pitch circle, or the number of teeth divided by the
transverse diametral pitch.
F) Tooth Form: Normally defined within a
detail view on the mechanical drawing, information delineated
is one or more of the following; Standard
addendum, long addendum, short addendum, modified involute or
other.
G) Maximum Calculated Circular Thickness on
Standard Pitch Circle: Tooth thickness which provides required
minimum backlash with gear assembled within mating gear at minimum center distance.
G1) Maximum Calculated Normal
Circular Thickness: Circular tooth thickness in the normal plane.
H) AGMA
Quality / Tolerance Class: Defines the accuracy of the gear.
J) Maximum Total Error: Cumulative or
actual tolerance
values permitted by the AGMA quality / tolerance class.
K) Maximum Tooth to Tooth Total Error:
Tolerance value is given within the AGMA quality / tolerance class.
L) Specification Master: This is used to
specify the check tool by part number or industry
specification for backlash or to verify gear interface
parameters.
M) Outside Diameter: This is the largest and
major diameter of the gear. The parameter is normally verified
with the mating Specification Master Gear.
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