Amazon.com Product Description
Designed for frequent use by serious woodworkers, the DELTA 17-787 1/2-inch Bit Set drills 1/2-inch square holes for making mortise and tenon joints. This bit's center drill bit removes material while its hollow chisel squares off the sides. Designed to fit DELTA mortising attachments, mortising machines, and boring machines, this bit features a 2-piece design for easy re-sharpening. This set includes one drill bit and one hollow chisel.
From the Manufacturer
Use this mortising chisel and bit set with mortising attachments or a dedicated mortising machine to drill square and rectangular holes for mortise and tenon joints. The two-piece design allows the drill bit to rotate and remove the bulk of the material while the hollow chisel maintains alignment to square off the sides of the hole. Constructed of a higher grade of steel, this set provides a longer-lasting, superior quality finish than the standard mortising chisel and bit sets. Includes one drill bit and one hollow chisel.