A sanitary clamp with facing ring halves employs one or more threaded closure devices configured to avoid having any threads exposed to the ambient. A bolt member may have a stepped shaft with a first smooth shaft portion and a male-threaded tip portion. The latter may be the same or a smaller diameter. An associated nut member has a blind bore that extends from a first end of the nut, with a first smooth wall portion and a second female threaded bore portion. The second female threaded portion may have the same bore diameter, or the bore can have a stepped interior diameter with the second female threaded bore portion having a diameter smaller than the first smooth wall portion. A seal member or gland within the smooth wall bore portion closes off a space defined between said the tip portion of the bolt member and the female-threaded bore portion. Once installed, there are no threaded surfaces of the bolt member or the nut member that are exposed to the ambient.