fibergalss hollow core bit
Fiberglass Core Bits are designed for drilling through utility poles made from fiberglass and/or composite materials.
Fiberglass Hollow Core Bits - High Speed Steel page 177C
High Speed Steel Fiberglass Hollow Core Bits were developed for major utility drilling through thick wall hollow core utility poles made from fiberglass/composite materials. They are manufactured with a ground short wide flute and narrow land and can be resharpened.
Fiberglass Solid Core Bits - Carbide Tipped page 177C