"A core drill is a drill specifically designed to remove a cylinder of material, much like a hole saw. The material left inside the drill bit ...
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is referred to as the core.
Core drills used in metal are called annular cutters. Core drills used for concrete are generally called Diamond Core Drills and are water cooled. For drilling masonry, carbide core drills can be used.
The earliest core drills were those used by the ancient Egyptians, invented in 3000 BC. Core drills are used for many applications, either where the core needs to be preserved (the drilling apparatus used in obtaining a core sample is often referred to as a corer), or where drilling can be done more rapidly since much less material needs to be removed than with a standard bit. This is the reason that diamond-tipped core drills are commonly used in construction to create holes for pipes, manholes, and other large-diameter penetrations in concrete or stone." - (en.wikipedia.org 26.11.2019)
