String Reamer : Reamer placed within the drill stem assembly that will increase the diameter of any keyseat through which it passes; used to remove doglegs and keyseats and to straighten the wellbore. (Bul D20)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}