Spreading plug for anchoring in undercut boreholes

A spreading plug for anchoring in an undercut borehole having a bottom, said spreading plug comprising a spreading body having an outer spreading surface and an end surface facing the bottom of the borehole;

• a plug shaft including a plurality of spreading segments extending in a direction toward said outer spreading surface and having inner surface means, said spreading segments being spreadable over said outer spreading surface upon axial displacement of said plug shaft relative to said spreading body;
• thread means connecting said spreading body and said plug shaft for enabling rotation of said plug shaft relative to said spreading body to provide for the axial displacement of said plug shaft relative to said spreading body, said plug shaft having a mounting portion facing away from said outer spreading surface and means provided on said mounting portion for cooperation with a rotary tool for rotating said plug shaft;
• a safety element projecting from said end surface of said spreading body for engaging the bottom of the borehole to prevent rotation of said spreading body upon rotation of said plug shaft;
• and means for facilitating displacement of said spreading segments over said outer spreading surface and comprising receptacle means formed in said inner surface means of said spreading means and sliding ring means arranged in said receptacle means for engaging said outer spreading surface and displacement thereover upon spreading of said spreading segments over said outer spreading surface.