Abstract: Test results have proved that the fractures in the long-tooth tricone carbide bits of XHP₃ and XHP₄ types for oil drilling are mainly caused by heat fatigue, mechanical fatigue and excessive impact load, abrasion of teeth being not prominent, and that most defects take the form of abrasive wear of particles, generally aggravated by heat fatigue. A description is given in the paper of the development of a new technology for making the cone bits which are resistant to heat fatigue, mechanical fatigue and impact load and of the treatment of the different parts of the bits according to the duties they are called on to perform.