Definition of pilot

i. A cylindrical steel bar extending through and about 8 in (20 cm) beyond the face of a reaming bit. It acts as a guide that follows the original unreamed part of the borehole and hence forces the reaming bit to follow and be concentric with the smaller-diameter, unreamed portion of the original borehole.

Synonym of: reaming pilot

Ref: Long

ii. A cylindrical diamond-set plug, of somewhat smaller diameter than the bit proper, set in the center and projecting beyond the main face of a noncoring bit.

See Also: pilot bit, stinger

Ref: Long