Under the same parameters, the author calculates the tooth thickness deviation of different tooth line radii in the same section, and its change trend is shown in Fig. 1.

It can be seen from Figure 1 that the tooth profile radius has different influence on the tooth thickness deviation of circular arc tooth profile cylindrical gear in different sections. In the middle section, the tooth thickness deviation is basically zero. The reason is that the tooth surface is obtained by scanning the involute equation along the tooth direction line for parallel linkage mechanism, and the tooth profile in any section is involute; for the gear machined by rotating cutter head, no matter what the value of tooth line radius is, the tooth profile is involute.

When the same basic parameters of involute equation (basic parameters of gear) are selected, the tooth thickness of the two machining methods is the same, so the basic deviation is basically 0. The reason of curve fluctuation in Fig. 1 (a) is due to measurement error.

In other arbitrary sections, with the increase of the tooth profile radius, the tooth thickness deviation gradually increases, and the tooth thickness gradually becomes thinner. When the tooth line radius is small, even the tooth profile curves on both sides of the tooth are dry and astringent (the tooth profile curves intersect).

The tooth profile of cylindrical gear with circular arc tooth line is shown in Fig. 2.

It can be seen from Figure 2 that when the gear line radius is close to or less than the gear width, the gear machined based on the rotary cutter head milling can be completely cut off. Therefore, the normal milling of circular arc tooth line cylindrical gear cannot be realized at this time.