Pilot Bit 2 : Bit with a smaller diameter than the hole finally to be drilled. Used on deflecting tools, such as the whipstock and knuckle joint. Also used with hole openers which follow and enlarge the original hole. (Bul D20)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}