Blind hole

A blind hole refers to a hole that is reamed, drilled, or milled to a specified depth without breaking through to the other side of the workpiece. The etymology is that it is not possible to see through a blind hole. Other types of holes also include through holes, and clearance holes. In this instance blind may also refer to any feature that is taken to a specific depth, more specifically referring to internally threaded hole (tapped holes).

There are three accepted methods of threading blind holes:

At least two U.S. tool manufacturers have manufactured tools for thread milling in blind holes: Ingersoll Cutting Tools of Rockford, Illinois, and Tooling Systems of Houston, Texas, who introduced the ThredMil in 1977, a device that milled large internal threads in the blind holes of oil well blowout preventers. Today many CNC milling machines can run such a thread milling cycle (see a video of such a cut in the "External links" section).

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