The known number of teeth Z1 = 23 Z2 = 45 modulus M = 4 pitch circle pressure angle 20 degree pitch circle pressure angle 23 degree Find the pitch circle diameter D1 D2 base circle diameter db1 pitch circle diameter D3 D4 actual center distance a

The known number of teeth Z1 = 23 Z2 = 45 modulus M = 4 pitch circle pressure angle 20 degree pitch circle pressure angle 23 degree Find the pitch circle diameter D1 D2 base circle diameter db1 pitch circle diameter D3 D4 actual center distance a

After calculation, the diameter of dividing circle D1 = 92, D2 = 180; the diameter of base circle db1 = 86.452, DB2 = 169.145
Actual center distance a = 138.834897 (no backlash engagement state)
Because the meshing angle (pitch circle pressure angle) is 23 °, this pair of gears is not a standard spur gear, but a positive drive with the total modification coefficient greater than 0. The total modification coefficient is 0.7608. Because the distribution modification coefficient is involved, the pitch circle diameter can not be determined now
If "it is indeed a standard spur gear" and the center distance is "intentionally" increased, then the pitch diameter D3 = 93.918 and D4 = 183.752

According to the national standard, the modulus and pressure angle on circle () of involute gear are standard values
B. Graduation
C. Base circle
D. Root of tooth

B. According to the national standard, the modulus and pressure angle on the dividing circle of involute gear are the standard values

Generally speaking, the standard pressure angle α of involute gear refers to the pressure angle on which circle

Dividing circle