Surgical devices and methods are provided for anchoring tissue to bone, and more particularly methods and devices are provided for preventing over-insertion of an expander into a sheath of a two-piece anchor. For example, a tendon anchoring system is provided with an anchor assembly and an inserter tool. The anchor assembly includes a sheath with a threaded lumen and a threaded expander screw configured to be threadably disposed within the sheath to cause the sheath to expand outward. The inserter tool includes an elongate outer shaft with a distal end configured to couple to a proximal end of the sheath, and an elongate inner shaft with a distal drive tip configured to engage a proximal end of the expander screw. In one embodiment, the inner shaft can be rotatable relative to the outer shaft to thread the expander screw into the sheath, and the inner shaft can be prevented from rotating relative to the outer shaft when the expander screw is fully threaded into the sheath to prevent over-insertion of the expander screw into the sheath.