Abstract: A safety shear tool for series connection into a string of sucker rod, especially a fiberglass sucker rod, which includes two coacting members connected together to form a swivel means, and to also form a shear means, so that the tool acts as a weak link as well as a swivel means. The tool is series connected into the sucker rod string and preferably located near the bottomhole pump. When the pump malfunctions and causes the tension in the sucker rod string to increase to a value less than but close to the designed breaking strength of the sucker rod string, the members of the tool are released, one from the other, thereby parting the sucker rod at the tool rather than parting the sucker rod structure itself. The tool is easily reassembled for subsequent use downhole in the above described manner. The set tension at which the tool parts the rod from the pump is easily changed.