Definition - What does Wing Cutter mean?
Wing cutters are special attachments at the cutting head of a directional drilling system. They are necessary when the job requires the boring to be slightly enlarged to facilitate casing installation. Wing cutters are designed to open when the drill proceeds in a forward direction (clockwise), and retract when the drill is reversed (counterclockwise).
Trenchlesspedia explains Wing Cutter
Enlarging the borehole using wing cutters is known as over-excavation. This is necessary since it makes insertion of case easier by minimizing the amount of friction generated from contact between the casing and the surrounding soil (skin friction).
Normally, a standard overcut of about 1-inch (25mm) is acceptable for most applications. The wing cutters are, however, adjustable to control the amount of over-excavation required.
Wing cutters are usually positioned so as to prevent over-excavation at the bottom of the casing which can cause the drill to deviate in a downward direction.