Pitch

Pitch

1. The distance between similar, equally spaced tooth surfaces, in a given direction and along a given curve or line.
2. The theoretical distance between corresponding points, on adjacent teeth. (Equal to the average of all spacing measurements, or generated by angular positioning devices).

Normal Pitch: The pitch in the normal plane, see diagram.

Transverse Pitch: The pitch in the transverse plane, see diagram.

Axial Pitch:
See Axial Pitch

Pitch Range:
The algebraic difference between the longest and the shortest measurement of pitch on the entire gear.
Pitch-Range Tolerance:
The allowable amount of pitch range.
Pitch Tolerance:
The allowable amount of pitch variation. (Equal to the algebraic difference of allowable pitch variations).
Pitch Variation:
The difference between pitch and the measured distance between any two adjacent teeth.

Normal Pitch

Transverse Pitch

Axial Pitch animation
Axial Pitch

Whereas:
From Gear Data
z = no. of teeth in gear (61)
M_n = normal module (8)
a_n = normal pressure angle (20)
ß = helix angle (15)
x = profile shift coefficient (0)

Calculated
a_t = Transverse pressure angle (20.647°)
Pn = Normal Pitch (25.133mm)
Pt = transverse (circular) pitch (26.0193mm)
Pbn = Normal Base Pitch (25.1327mm)
Pbt = Transverse Base Pitch (24.348mm)
Pbt = Axial Pitch (97.1054mm)

Formula:

Normal Pitch: Pn
= M_n*Pi
= 8*3.141592654
= 25.133mm

Transverse (Circular) Pitch: Pt
= (M_n*Pi)/cos(ß)
= (8*Pi)/cos(15)
= 25.13274123/0.965925826
= 26.0193mm

Normal Base Pitch: Pbn
= Pi*M_n*cos(a_n)
= 3.141592654*8*cos(20)
= 3.141592654*8*0.93969262
= 25.1327mm

Transverse Base Pitch: Pbt
= Pt*cos(a_t)
= 26.0193*cos(20.647)
= 26.0193*0.9357706
= 24.348mm

Axial Pitch: Px
= (M_n*Pi)/sin(ß)
= (8*3.141592654)/sin(15)
= 25.13274123/0.258819045
= 97.1054mm

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