Discussion on some skills, methods and precautions of bearing installation (interference assembly) (bearing heater) Shaft bearing installation (interference assembly) skills and precautions
Whether the bearing is installed correctly or not directly affects the accuracy, life and performance of the bearing in use.
⒈Using copper rods and manual hammering to install
This is an easy way to install small to medium bearings. When the inner ring of the bearing has a tight fit and the outer ring has a loose fit, place the copper rod against the end face of the inner ring of the bearing, directly hit the copper rod with a hammer, and transmit the force through the copper rod to slowly install the bearing on the shaft. When the inner ring of the bearing is large, the copper rod can be used to strike evenly around the end face of the inner ring of the bearing. Do not strike only one side, and do not use too much force. It should be struck symmetrically, lightly and slowly installed, so as to prevent the bearing from being slanted and cracked.
⒉ Using sleeve to install This method is the same as using the copper rod to install the bearing. It presses the sleeve directly on the end face of the bearing (the end face of the inner ring is pressed when the bearing is installed on the shaft; the end face of the outer ring is pressed when it is installed in the housing hole), and the hammering force can be evenly distributed in the installation. The end face of the entire ring of the bearing can be used in conjunction with the press, which saves labor and time in installation and has reliable quality. Sleeves for installation should be made of soft metal (copper or mild steel pipe). If the bearing is installed on the shaft, the inner diameter of the sleeve should be slightly larger than the journal 1-4mm, and the outer diameter should be slightly smaller than the diameter of the rib of the inner ring of the bearing, or the thickness of the sleeve should be made equal to the thickness of the inner ring of the bearing. 2/3-4/5, and both ends of the sleeve should be flat and perpendicular to the barrel. If the bearing is installed in the seat hole, the outer diameter of the sleeve should be slightly smaller than the outer diameter of the bearing.
3. There is also a press-in method: the installation pressure should be directly applied to the end face of the bearing ring with interference fit, otherwise it will cause pressure injury on the bearing working surface, resulting in the bearing being damaged quickly.
4. Heating installation
For bearings with large interference or large-size bearings, in order to facilitate installation, the principle of thermal expansion and cold contraction can be used to install the bearing with copper rods, sleeves and hand hammers after heating in the oil tank. When heating, the temperature is generally controlled below 100 °C, and 80-90 °C is more suitable. When the temperature is too high, it is easy to cause annealing of the raceway and rolling elements of the bearing ring, affecting the hardness and wear resistance, resulting in reduced bearing life and premature scrapping.
The fit between the bearing and the shaft is generally a transition fit, and the fit between the seat ring and the bearing seat hole is generally a clearance fit. The center collar of a two-way bearing should be fixed on the shaft to prevent rotation relative to the shaft. The installation method of the bearing is generally the case where the shaft rotates, so the fit between the inner ring and the shaft is an over-win fit, and the fit between the outer ring of the bearing and the bearing chamber is a clearance fit.
When installing the bearing, first fix the dial indicator on the end face of the case, so that the contact head of the indicator is on the bearing shaft ring raceway to rotate the bearing, and observe the dial indicator pointer while rotating. The axis centerline is not vertical. If the casing hole is deep, the extended dial indicator can also be used for inspection. This is a good way to check the squareness of the collar and the centerline of the shaft.
If the bearing is installed backwards, not only does the bearing work abnormally, but also the mating surfaces will be severely worn. Since the difference between the shaft washer and the seat washer is not obvious, extra care should be taken during assembly to prevent reverse assembly. When installed correctly, the race should be able to automatically adapt to the rolling of the rolling elements to ensure that the rolling elements are located in the upper and lower raceways. In addition, there should be a gap of 0.2-0.5mm between the bearing seat ring and the bearing seat hole to compensate for errors caused by inaccurate parts processing and installation. When the center of the bearing ring is offset during operation, This clearance ensures that it adjusts automatically, avoiding contact friction and allowing it to function properly. Otherwise, the bearing will be severely damaged.
Precautions during installation:
For the Harbin bearing ring with clearance fit, it is recommended to apply a thin layer of anti-creep corrosion agent on the mating surface to prevent frictional corrosion between the mating surfaces.
2. The force exerted on the bearing during installation must not be transmitted from one bearing ring to another through the rolling elements, otherwise the raceway may be damaged. However, under no circumstances should the bearing rings, cages, rolling elements or seals be struck directly.
3. Install eccentric sleeve. First put the eccentric sleeve on the eccentric step of the inner sleeve of the bearing, and tighten it by hand along the rotation direction of the shaft. Then insert the small iron rod into or against the countersunk hole on the eccentric sleeve. Hit the small iron rod with a hammer in the direction of rotation of the shaft. Install the eccentric sleeve firmly, and finally tighten the hexagon socket head cap screw on the eccentric sleeve.
4. Do not tighten the bolts fixing the bearing seat first, so that the bearing shell can rotate in the bearing seat. Re-tighten the bearing housing bolts. Also install the bearing and seat on the other end of the same shaft, turn the shaft a few times, and let the bearing itself find the correct position automatically.
5. Apply lubricating oil on the mating surface of the bearing seat and the bearing, and install the Harbin bearing into the bearing seat. Then put the assembled bearing on the shaft together with the bearing seat. Push to the desired location for installation.