Abstract: A high-temperature, low-thermal expansion fastener for joining low thermal expansion refractory materials includes a pin with an inset portion on the shank of the pin that forms a head-facing shoulder, at least one shell insert which is seatable about the inset portion, and an internally threaded member which can be screwed onto the threaded outer surface of the shell inserts to maintain the inserts in abutting relationship with the inset portion. Forces within the fastener are transferred from the internally threaded member to the shell inserts which in turn press against the head-facing shoulder on the pin shank to place the shank in tension. The fastener parts, including a spacer, may be selected to compensate for thermal expansion or contraction of the fastened elements.