The coal bits mainly used in coal and mine drilling.We can do different measures according to customer's requirements or drawing type one Colliery Tools Main Standard(mm)DHLM274417 M14×1.5275417 M12×1.75Thread285420 M12×1.75joint295218 M14×1.5305018 M14×1.5325222 M14×1.5325622 M12×1.75 type 2 Colliery ToolsMain Standard(mm)DMThread Joint381240124212