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Points to note for NTN bearing assembly

Source:  skf bearing  Time:  2020-11-30

NTN bearing pre-tightening force is carried out at room temperature, but in working condition, the drive shaft and bearing pre-tightening force produced by the system's micro-stretching temperature rise will change. Therefore, you should consider this when setting the pre-tightening force. factor.


It needs the capacity, speed, and other conditions to set the reasonable use of the bearing preload to ensure the life of the transmission. If the pre-tightening force is too large, the power consumption will increase and even lead to overheating. If the pre-tightening force is too small, the body load, shaft rolling, and the gap between the outer rings will cause beating, transmission accuracy to reduce noise increase, affect gear meshing, and seriously damage teeth and bearings.


According to different NTN bearing assembly, such as: the bearing pre-tightening nut rotates directly by axially compressing the inner bearing inner ring, the inner and outer rings, to eliminate the gap and realize the purpose of bearing pre-tightening force. At present, the realization of common use: first, far more than the pre-installed bearing, the nut at the end, and then back 1/4 turn. Assembling method, the advantages of this method are low investment, simplicity, practicality, and consistent quality of tapered roller bearings. It can be used.


It works smoothly, reliably, and without noise under sliding friction. The sliding bearing of the lubricant on the liquid surface does not directly contact the separated lubrication conditions, and it can also greatly reduce the surface friction loss and wear. The film also has a certain shock absorption capacity. NTN bearings are widely used. Problems with bearing failures:


1. Ceramic tile surface corrosion: spectrum analysis found that the concentration of non-ferrous metal elements is abnormal; ferrography, there are many sub-micron penetrating particles of non-ferrous metal parts; excessive moisture in lubricating oil, excessive acidity.


2. NTN bearing journal surface strain: ferrograph cutting abrasive or black iron oxide particles, temper color metal surface.


3, NTN bearing journal surface corrosion: spectrum analysis found that abnormal concentration of iron, iron spectrum, there are many iron content in sub-micron particles, excessive moisture or acid oil exceeding the standard.


4. The strain on the surface of NTN bearing: Ferrograph cutting abrasives, composed of non-ferrous metals.


5. Micro-motion of tile back: spectrum analysis found abnormal level of iron, iron spectrum, there are many wear particles with iron content in submicron, water-in-oil and acid abnormalities.
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In the assembly where the assembly of tapered bearings is difficult, the pre-tightening force NA of tapered bearings directly affects the state of the drive bevel gear transmission system and the accuracy of the transmission.


The NTN bearing oil heating method is the most commonly used temperature difference method. The heating oil should be non-corrosive mineral oil, and the transformer oil with the best flash point above 250 degrees. When assembling the bearing, the oil bath heating method can be used. When disassembling NTN bearings, you can use the heating method of hot oil pouring.


When using an oil bath to heat NTN bearings, a thermometer should be used to control the oil temperature to prevent overheating. At the same time, the bearings should be placed on a screen or bracket 50-70 mm away from the bottom of the box. Do not directly contact the bottom of the box to prevent local temperature of the NTN bearing. The rise is too high and affected by the dirt in the oil.


NTN bearing anti-wear and extreme pressure additives can generally be divided into two categories: oily agents and anti-wear extreme pressure agents:


Oily additives: NTN bearing oily additives form a physical adsorption film on the metal surface to improve the friction function of the metal contact surface and enhance the lubrication effect. Commonly used oily additives include: animal and vegetable oils, higher fatty acids, esters, alcohols and other metal soaps.


Anti-wear and extreme pressure agents: NTN bearing anti-wear and extreme pressure agents are mostly organic compounds with strong chemical activity. This type of compound does not have a lubricating effect at room temperature, but can generate a relatively dense chemical film on the metal surface under high temperature and high pressure. This film generally has a lower melting point than the original metal material, and has a lower shear strength. When the metal surface rubs, it wears and prevents scratches.