US Patent 11458373 Golf club heads with internal undercuts

Described herein is a hollow body iron-type golf club head having a sole and ballast configured to relieve stress within a forward portion of the sole. In a first configuration, the golf club head comprises a ballast undercut for relieving stress. In other configurations, the ballast undercut is combined with additional stress relief features, such as a cascading sole near the face sole juncture, for further reductions to face thickness.