Union Butterfield 1578(UNC) High-Speed Steel Spiral Point Tap, Screw Thread Insert, Uncoated (Bright) Finish, Round Shank With Square End, H2 Tolerance, 1/4"-20 Thread Size Spiral point tap pushes chips ahead of tool to reduce clogging Spiral point tap and straight flutes for cutting threads in through holes Oversized tap for producing threads that will receive a helical coil wire screw thread insert (STI) of the same nominal size and pitch. Relieved-style design reduces friction between tap and workpiece for reduced tool wear Plug chamfer for easier starting and correct perpendicular alignment