Trepanning is the process of creating a hole or circular opening by removing a core, in this case by machining. Wachs DynaPrep MDSF split frames have been used successfully for trepanning access holes, manholes, stub-ins, bearing pockets, pipe, flat plates and more. Unlike ordinary single purpose drills, when trepanning is complete the MDSF serves as the foundation of the world’s most complete weld prep machining system.