Patent ID: 8025587

Claim:
A golf club head comprising: a body having a striking face defining a forward end of the club head, the body also having a rear end opposite the forward end, and a lower surface defining a recess and at least one threaded opening; and an adjustable sole portion that is adjustable relative to the body to adjust a sole angle of the club head, the adjustable sole portion being configured to be received at least partially within the recess in the lower surface, the adjustable sole portion having at least one opening that is aligned with the threaded opening in the lower surface of the club head body when the adjustable sole portion is received in the recess; and at least one threaded fastener configured to extend through the opening in the adjustable sole portion and into the threaded opening of the lower surface of the club head body so as to secure the adjustable sole portion to the club head body within the recess; wherein an effective face angle of the club head is substantially constant upon changing the lie angle of the club head from an initial lie angle to another lie angle that is at least 2 degrees from the initial lie angle; wherein the effective face angle is determined from the equation: eFA = - a ⁢ ⁢ tan [ ( sin ⁢ ⁢ Δ ⁢ ⁢ lie · sin ⁢ ⁢ G ⁢ ⁢ L · cos ⁢ ⁢ M ⁢ ⁢ F ⁢ ⁢ A ) - ( cos ⁢ ⁢ Δ ⁢ ⁢ lie · sin ⁢ ⁢ M ⁢ ⁢ F ⁢ ⁢ A ) cos ⁢ ⁢ G ⁢ ⁢ L · cos ⁢ ⁢ M ⁢ ⁢ F ⁢ ⁢ A ] where Δlie=measured lie angle−scoreline lie angle, GL is the grounded loft angle of the club head, and MFA is the measured face angle.