... 2100 90.0 For coring crowns, electric coal drill bits, coal cutting picks, oil cone bits and ... knife bits, usd in geological prospecting, coal mining and oil well boring.YG814.7 2400 89.5 For ... coring crowns, electric coal drill bits, coal cutting picks, ... knife bits, used in geological prospecting, coal mining and oil well boring.YG8C14.82450 88.5 Mostly used ...