Diamond core drills are used for hard building materials processing: for hole drilling in very thick walls from reinforced concrete, for gas and sanitary tubes laying, etc.
They consist from steel core and cutting segments welded to it. Segments inner overhang helps to take kern out easily.
Drills core has a shank 1 1/4 UNC. The maximum cutting depth (with the standart core) is 450 mm. To increase the cutting depth it is possible to use special 1 1/4 UNC drill collars of 100, 200, 300, 400, 500, 1000 mm length.