Spiral drill with boring cutter adds one or more reaming cutters of larger diameter and boring cutter has guide faces and center flushing or lubricating channel.

摘要

The twistdrill uses one or more reaming cutters (21,-23) spaced in the rotation sense at 25-30 deg round the boring cutter (3) and of larger diameter than the boring cutter. The drill center tip runs straight (15) and the remaining cutters have bevel faces to guide the drill, the faces being of different width. The reamer cutter faces (11,33,35,37) should be undercut and the drill has an inside channel (5) for flushing and/or lubricating fluid.