The assembly of a shaft member and a shaft end adapter which are manufactured separately can be accomplished with a high precision in coaxiality and straightness at a high efficiency. A tubular portion is formed with a circumferentially continuous portion at least in a part thereof adjoining a free end thereof, and a slit extends axially through a wall of the tubular portion in exclusion of the circumferentially continuous portion. A fastening bolt configured to close the slit is mounted on the tubular portion.

A steel pipe pile and a steel pipe column is connected using a steel pipe socket. The connection method may include preparing the steel pipe socket including a socket supporting portion that covers an upper end surface of the steel pipe pile, and inserting a plurality of socket insertion portions extended downward from the socket supporting portion and having a plurality of socket grooves at a lower end portion thereof and a plurality of fastening members installed on the socket supporting portion. The method may also include inserting the socket grooves of the steel pipe socket into an upper end portion of the steel pipe pile and mounting the steel pipe column on the socket supporting portion. The method may further include fastening the steel pipe column and the steel pipe pile using the plurality of fastening members of the socket supporting portion.

A hollow shaft coupling for connecting a shaft to a hollow shaft, where the hollow shaft coupling can be arranged completely in the hollow shaft and can effect clamping both radially inwardly as well as radially outwardly. The coupling enables a first clamping unit to clamp the hollow shaft coupling radially inwardly against the shaft and a second clamping unit which is separate from the first clamping unit to clamp the hollow shaft coupling radially outwardly against the inner circumferential surface of the hollow shaft, with the two clamping units spaced apart from one another axially, and the two clamping units connected to one another via a play-free and rotationally stable coupling which is arranged between them.