Installing or removing bearings on tapered shafts or sleeves is usually a difficult and time-consuming project. Using hydraulic nuts can improve work efficiency and reduce such problems. Therefore, in this article, TorcStark will introduce in detail the use of hydraulic nuts for the mounting and removal of bearings.

Hydraulic nut structure and working principle

Hydraulic nuts are different from standard locking nuts. Although they all have internal threads, their function is not to lock, but to adjust the bearing clearance by hydraulic propulsion. Hydraulic nuts are generally used for the installation and removal of tapered-bore spherical roller bearings, or large tapered-bore spherical roller bearings with adapter sleeves and withdrawal sleeves.

The hydraulic nut consists of two main parts, one is a nut with a groove at one end, and the other is an annular piston that fits in the groove. Its oil seal consists of two O-shaped sealing rings. When the nut is connected to the oil pump, the engine oil (oil viscosity is 300 mm2/s, and the maximum allowable pressure is 100 MPa) is pushed outward by the high-pressure piston, forming a large enough axial force to install or remove the bearing.

Advantages of hydraulic nuts

1. Suitable for various vibrations, fast rotation, high-force equipment and narrow spaces;

2. Economical and efficient, lightweight and high precision;

3. Can be equipped with manual hydraulic pumps, pneumatic hydraulic pumps and electric hydraulic pumps;

4. Multiple hydraulic nuts can be used at the same time;

5. No need to use a gauge, but can use the measuring ring in the structural design to accurately and stably measure the axial approach distance required by the bearing directly;

6. When installing and removing the withdrawal sleeve, the same specification of hydraulic nuts can be used, which is not available for hydraulic nuts with patented designs such as attached gauges or hanging connecting blocks;

7. Using the measuring ring and additional screws to disassemble the nut to replace the damaged O-ring saves time and parts cost compared to the general design;

8. Sealed bearings can be installed without measuring the internal clearance of the bearing to determine the axial approach of the bearing

Hydraulic nuts for mounting and dismounting bearings

Take the bearing with the withdrawal sleeve as an example.

During mounting, tighten the hydraulic nut and withdrawal sleeve and install the piston end on the withdrawal sleeve with the piston facing outward. Leave a gap slightly larger than the installation distance between the hydraulic nut and the bearing, screw the round nut on the shaft and tighten the piston. First pump the engine oil into the hydraulic nut. As the pressure increases, the withdrawal sleeve will slide smoothly into the bearing. After reaching the predetermined position, unload and drain the engine oil. Keep the withdrawal sleeve and the bearing in place for a while, and finally unscrew the hydraulic nut, replace the locking nut and check the bearing clearance.

When removal, the piston end of the hydraulic nut should be installed on the withdrawal sleeve facing the bearing, and the piston should be slightly tightened to make it close to the inner ring of the bearing, and then the engine oil should be pumped in until the bearing is loose.

If the oil groove is machined on the outer surface of the withdrawal sleeve and two oil inlets are attached, during installation or disassembly, the engine oil is pumped into the contact surface between the withdrawal sleeve and the bearing through the two inlets, and a high-pressure oil film is formed between them, which can greatly reduce the friction resistance. In this way, when used in combination with the hydraulic nut, the working effect will be better.

Advantages of hydraulic nuts for mounting and removing bearings with withdrawal sleeves

(1) It saves effort and time, is easy and quick to install and disassemble, and can precisely control the bearing clearance and improve assembly accuracy.
(2) Since the force is evenly applied, it will not damage the bearing contact surface, and there is no need to worry about the adapter sleeve or withdrawal sleeve being twisted.
(3) It can be standardized, serialized, and universalized.


Hydraulic nuts are used for bolts that need to be frequently disassembled and assembled; pre-tightening of oversized bolts; locking of large workpieces, etc., and can be used as hydraulic interference connection disassembly and assembly tools. Now, TorcStark provides high-quality and low-cost hydraulic nuts. If you have any needs, please feel free to contact us.