Integral Drill Steels are normally produced from 19mm (3/4" ), 22mm ( 7/8") or 25mm (1") Hexagon Drill Steel, where the dimensions given are measured across the flat of the hexagon.
Integral Drill Steels are a fixed length with a shank at one end and a bit at the other, and are able to drill to a depth equivalent to their effective length. The bit may consist of a single chisel shaped tungsten carbide insert or three such inserts.
To drill deep holes, the rods are designed to be used in a series where the length of any rod used is longer than the one used just before it. To do this, a series of rods must be produced so that the bit diameter is reduced for each increase in length of rod to prevent jamming of the bit in the hole.

Integral Drill Steels are normally produced from 19mm (3/4" ), 22mm ( 7/8") or 25mm (1") Hexagon Drill Steel, where the dimensions given are measured across the flat of the hexagon.
Integral Drill Steels are a fixed length with a shank at one end and a bit at the other, and are able to drill to a depth equivalent to their effective length. The bit may consist of a single chisel shaped tungsten carbide insert or three such inserts.
To drill deep holes, the rods are designed to be used in a series where the length of any rod used is longer than the one used just before it. To do this, a series of rods must be produced so that the bit diameter is reduced for each increase in length of rod to prevent jamming of the bit in the hole.