Optical drill collar position verifier

Abstract

A drill collar position verifier for use with a drill bit having a drilling depth control collar positioned coaxially thereon. The drill bit is inserted in a cylindrical opening in a plastic block to a depth determined by the position of the collar. Three optical beam sources are positioned at three different predetermined depths in the plastic block. Each optical beam source projects an optical beam across the cylindrical opening and onto a corresponding optical beam detector, unless the drill bit breaks such optical beam projections. The optical beam detectors are connected to logic circuitry which is further connected to LED indicators. If the drill bit protrudes far enough through the plastic block to break the first but not the second and third optical beams, an LED is lit to indicate that the collar is positioned too close to the tip of the drill bit. If the drill bit protrudes far enough through the plastic block to break the first and second but not the third optical beam, an LED is lit to indicate that the collar is positioned within tolerances. And, if the drill bit protrudes far enough through the plastic block to break all three optical beams, an LED is lit to indicate that the collar is positioned too far away from the tip of the drill bit.