This Threaded ID Drill Bushing (Internal Diameter) is precision machined from O-1 Tool Steel.  Each piece is subsequently heat treated and tempered.  This results in an extremely hard tool which is almost impervious to wear from the drill and the drilling chips. 

The external thread on the bushing is 1/2" -13 TPI.  We stock common Internal Diameter sizes to accommodate the drill sizes for standard aircraft fasteners.

Other Internal Diameter sizes can be custom ordered and machined on request.