8 1/2  Replaceable roller bits 

 Roller bit is a kind of cut pick use in deep foundation drilling work, it usually installed in core barrel, suite for very hard rock layer drilling. 
 When you start a doundation deep foundation work such as bored pile, pillar, drill shaft, cassion pile work, the layer is very hard 
drilling use bullet teeth, roller bit will be a best option. 

 Our roller bit have two type, one type no holder, is not replaceable type, direct welding on drilling tools（core barrel）. Another type is replaceable type, 
 it has holder welding on drilling tools(core barrel), can replace the roller bit easily.