The inspection chip (2) is configured so as to satisfy the following relationships: Angle (A) < Angle (B) < Angle (C); Angle (A) < Angle (D); Angle (D) < Angle (B).

The first or inner cord helix angle is greater than a second or outer cord helix angle.

The first angle is smaller than the second angle.

The first angle is different from the second angle.

The joint angle is variable over an angular range that includes a first angle and a second angle.

The first angle is larger than the third angle.

The first angle (α) is different from the second angle (β).

The new gamma firing angle is provided as the initial gamma firing angle and a new gamma firing angle is calculated.

The first angle α = 6º ± 1º, the second angle α2 = 8º ± 1º and the third angle α 3 = 19º to 25º.

The first angle is formed relatively greater than the second angle.