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)
	D	H	L	M
	27	44	17	M14×1.5
	27	54	17	M12×1.75
Thread	28	54	20	M12×1.75
joint	29	52	18	M14×1.5
	30	50	18	M14×1.5
	32	52	22	M14×1.5
	32	56	22	M12×1.75

type 2

Colliery Tools	Main Standard(mm)
	D	M
Thread Joint	38	12
	40	12
	42	12