... raw material through special heat treatment ,especially, tungsten carbide of tapered button bits are from Boart long year ... ,6,7,11,12 degree, premium alloy tapered drill steel with Hexagonal .22mm and Hexagonal.25mm, The ... .Product featuresPremium designs and steel and premium tungsten carbide insert grade T6 supplied by Boart Long year, ... up fuel cost rate.Technical Specifications carbide drill Bits