Drilling and hole enlargement device

An expandable drilling apparatus connected to a drillstring, the drilling apparatus comprising:

• a cutting head disposed upon a main body, wherein the main body comprises a plurality of axial recesses adjacent to the cutting head;
• a plurality of arm assemblies retained within the axial recesses, wherein the arm assemblies are configured to translate from a retracted position to an extended position along a plurality of grooves formed into walls of the axial recesses;
• a drive piston configured to thrust the arm assemblies into the extended position when in communication with fluids flowing through the drillstring;
• and
• a selector piston configured to allow fluids flowing through the drillstring to communicate with the drive piston when an activation pressure is exceeded.

A method of drilling a borehole comprising:

• disposing a drilling assembly having expandable arm assemblies adjacent to a cutting head upon a distal end of a drillstring;
• drilling a pilot bore with the cutting head;
• underreaming the pilot bore with cutting elements of the expandable arm assemblies;
• stabilizing the drilling assembly with stabilizer pads of the expandable arm assemblies.