The invention relates to a 
nitrogen spring type hydraulic chuck, and in particular relates to a drilling tool for a clamping drilling 
machine, belonging to the mechanical technical field of the drilling 
machine. The 
nitrogen spring type hydraulic chuck mainly comprises a 
piston rod, a 
piston, a cylinder 
barrel, a chuck upper shell, slip bowls, spring seats, a 
nitrogen spring and a slip element, wherein the 
piston rod is arranged on the chuck upper shell, the cylinder 
barrel is sleeved on the outer ring of the 
piston rod, the piston is in a piston chamber between the 
piston rod and the cylinder 
barrel, slip bowls are arranged on the 
piston rod and the inner ring of the chuck upper shell, the spring seats are fixed on the lower flanged end faces of the slip bowls; and the lower end of the nitrogen spring is fixed on the spring seats. The nitrogen spring type hydraulic chuck has a simple, compact and reasonable structure; by using nitrogen as the chuck elastic element, the changes of the elasticity are little and the performance is stable; the nitrogen spring has long service life and is convenient for replacement and maintenance; the 
hydraulic pressure of the oil line is utilized to realize full-
process control; the 
hydraulic pressure is utilized to control the drilling tool to clamp or loosen; and the slope structure of the slip element is used to convert an 
axial force to a radial force, thus the clamping force of the chuck is increased.