... Stable quality and sound performance ISO certificate Carbide tips for well drilling:Physical properties for the mining tool parts:Grade Density(g ... knife bits, applied in geological prospecting, coal mining and oil well boring.YG814.8≥2320≥89.5For coring crowns, electric coal ... knife bits, used in geological prospecting, coal mining and oil well boring.YK0514.8≥2500≥90.5Mostly used as the buttons ...