Rolling bearings are precision mechanical parts, and whether they are installed correctly or not directly affects the accuracy, life, and performance of the bearing. Therefore, the installation and disassembly of the bearing must adopt correct methods and use appropriate tools.
The installation and disassembly of the rolling bearing are divided into the installation and disassembly of the cylindrical bore bearing and the tapered bore bearing. The installation and disassembly methods of the cylindrical bore bearing mainly include the press-in method and the heating or cooling method.
01 Maintenance before installation
1. Overhaul of shaft
(1) Check the eccentricity, bend, and roundness of the journal, place the shaft on the two centers of the lathe, or place it on a cast iron plate supported by 120°V-shaped iron, and use a dial indicator pointer to contact the journal that matches the bearing, And then slowly rotate the shaft to observe the swing of the dial indicator pointer on the journal. If the shaft rotates once, the pointer only swings to one side and then returns to the original position, which indicates that the shaft is eccentric or bent. The amount of eccentricity or bending is half of the swing value of the dial indicator pointer; if the shaft rotates once, the dial indicator After the pointer swings twice, it returns to its original position, indicating that the journal is elliptical, and the difference between the maximum and minimum index of the dial indicator is the roundness value. When the eccentricity and curvature of the shaft are greater than the specified value, repair measures should be taken.
(2) Check the surface roughness of the journal. When the roll journal has burrs or bruises, it should be treated first, and then polished with a fine emery cloth.
(3) Check the verticality of the shaft shoulder of the journal and the fillet radius of the root of the shaft shoulder. The verticality of the shaft shoulder shall be tested with a 90° square. The fillet at the root of the shaft shoulder can be inspected with a fillet template. If the fillet is too large, the bearing and the shaft shoulder will not be tightly attached, which will easily cause vibration during use and easily cause the bearing inner ring to break; if the fillet radius is too small, the strength of the shaft will be affected. Therefore, the fillet radius at the root of the shaft shoulder must be smaller than the fillet radius of the inner ring of the bearing, and generally should be 1/2 of the fillet radius of the inner ring of the bearing to ensure that the end face of the bearing is close to the shoulder.
(4) The size of the inspection journal can be inspected with a micrometer or a dial indicator. When the journal is severely worn, the size is smaller than the specified matching requirements, and the inner diameter of the bearing inner ring is loose, the journal should be repaired, or contact a DMD engineer for consultation.
2. Inspection and repair of the inner hole of the bearing box
(1) Check the roundness and cylindricity of the inner hole: use an inner diameter micrometer to inspect, or a special dial gauge holder for measuring the inner hole.
(2) Check the verticality between the hole in the box and the stop shoulder of the hole: when the stop shoulder of the hole is not perpendicular to the centerline of rotation, the load is likely to concentrate on the rolling elements of the bearing, causing uneven forces and creeping, And make the raceway bear too much load, resulting in deformation and affecting life.
(3) Check the amount of wear and coaxiality of the inner hole of the bearing box: The inner hole of the bearing box is often out of the center due to wear deformation or boring processing errors. If they are not concentric, the shaft will tilt after installation, the bearing will be stuck, or even the bearing housing shell will bend and crack.
(Note: Use a cast iron platform, and use 2 fulcrum inner holes to locate and detect coaxiality.)
02 Cleaning before installation
New bearings are coated with anti-rust grease. The main function of these greases is to prevent rust and not lubricate. Therefore, the bearings should be thoroughly cleaned before installation and use. Rolling mill bearings, are generally sealed with anti-rust oil and can be cleaned with gasoline or kerosene. Extra-large bearings can be wiped clean with gasoline or kerosene.
To clean the inner hole of the shaft and the bearing box and other parts, first clean it with gasoline or kerosene, clean it with a dry silk (or dry nylon cloth) cloth, and then apply a small amount of oil for installation. After cleaning these parts, it should be noted that all casting sand on the castings should be completely removed; all burrs and sharp corners on the parts matching the bearing must be removed to prevent residual sand and metal chips from falling into the bearing during installation, affecting Assembly quality.
03 Installation and disassembly of bearing inner hole
Press-in method for cylindrical bore bearing installation and disassembly When using the press-in method to install, the installation pressure should be directly applied to the end face of the bearing ring of the interference fit, and it is absolutely not allowed to transmit pressure through the rolling elements, Otherwise, it will cause damage to the bearing raceway surface, leading to premature bearing failure; if the bearing will continue to be used after it is removed, it is also not allowed to transmit pressure through the rolling elements during disassembly; the mechanism should be designed to facilitate the disassembly of the bearing. Special tools should be used for the operation.
Installation and disassembly of cylindrical bore bearing heating method： When using the heating or cooling method to install, the more suitable heating temperature range is 80 ~ 100 ℃, the highest should not exceed 120 ℃. Common heating methods mainly include oil bath heating and induction heating.
Installation and disassembly of bearings with tapered bore： Bearings with tapered bores are always installed with an interference fit. The amount of interference depends on the length of the thrust of the bearing on the tapered journal or tapered adapter sleeve. The radial clearance of the bearing is reduced during the process of pushing in. The size of the push-in amount determines the degree of fit. The radial clearance can be continuously measured during installation until the required radial clearance and ideal press fit are reached.
Please check our Product Guide to select the suitable bearings for your machines.
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