An apparatus can include a plate member having a top surface, a bottom surface and a hole extending between the top and bottom surfaces. The plate member hole can have a spherically shaped sidewall. A right-hand helical thread can be formed in the sidewall of the plate member hole, and a left-hand helical cut can be formed in the sidewall of the plate member hole intersecting the right-hand helical thread. The left-hand helical cut can be configured to reduce a portion of a contact surface area of the right-hand helical thread and the sidewall of the plate member hole.
