What are the installation steps for self-aligning roller bearings?

The installation steps for self-aligning roller bearings need to be adjusted flexibly based on the type of bearing, installation environment, and the type of fit (interference fit / clearance fit). The following is a general standardized process covering the four core steps of preparation, heating (if necessary), installation, and inspection, along with key precautions:
1. Preparations before installation
1.1 Part cleaning and inspection
Bearings cleaning: Remove rust and dust from the bearing surface using kerosene or dedicated cleaning agents, ensuring that the raceways and rollers are free from scratches (use a lint-free cloth to wipe, avoiding cotton fibers). The surface roughness of the mating surfaces needs to be ≤ Ra1.6 μm, and the dimensional tolerances should be in accordance with the drawings (such as interference fit: the tolerance of the shaft neck is h6, the tolerance of the seat hole is H7). Use a micrometer or plug gauge to measure, and if the error exceeds 0.01mm, rework is required.
Shaft shoulders / seat hole shoulders perpendicularity ≤ 0.02mm (check with a right-angle ruler), to avoid the bearing from being skewed after installation.
1.2 Tools and auxiliary materials preparation
Installation tools:
Interference fit: Induction heater (recommended), oil bath tank (temperature ≤ 120℃), copper rod (avoid direct impact on the bearing), hydraulic nut (for large-sized bearings).
Clearance fit: Socket wrench, press fitting tool (apply uniform pressure on the inner or outer ring).
Lubrication materials:
If lubrication is required during installation, use lithium-based grease (NLGI 2 grade) or mineral oil (viscosity 46cSt). Avoid using grease containing solid particles.
Pre-lubrication of the bearing requires confirming the grease type. If the heating temperature is > 100℃, the parts need to be pre-cleaned and re-lubricated.
2. Environmental control
The installation site should be dust-free (air particles ≤ 50μm), to prevent dust from entering the bearing interior; the environmental temperature should be maintained at 20℃ - 25℃, and in winter, parts need to be preheated to room temperature (≥ 10℃).
2.1 Heating installation process for interference fit bearings (core steps)
1.1 Calculation and execution of heating temperature
Temperature determination: Calculate based on the interference amount (refer to the previous question), generally controlled at 80℃ - 120℃. Use an infrared thermometer to monitor the temperature of the inner ring of the bearing (when using an oil bath heater, the bearing needs to be suspended in the oil tank, avoiding contact with the bottom of the tank, with the oil surface higher than the bearing by 50mm).
Heating time: The heating time for each 100mm of the bearing diameter is approximately 15 minutes (for a 100mm inner diameter bearing, heat to 100℃ and then maintain for 15 minutes to ensure uniform expansion).
2.2 Quick installation and positioning
Key points:
After heating, remove the bearing with heat-resistant gloves and insert it into the shaft neck within 1 minute (align with the key slot or positioning mark), the axial thrust needs to be applied to the inner ring (avoid transmitting force through the rollers).
During installation, use a copper rod to gently tap the end face of the inner ring or use a press fitting machine to apply uniform pressure until the inner ring of the bearing is completely in contact with the shaft shoulder (use a feeler gauge to check the gap ≤ 0.03mm).
Axial positioning: Achieve fixation through shaft retaining rings, locking nuts, or the self-fit of the interference fit itself. The tightening torque of the nut needs to be calculated according to the formula (e.g., M = K × P × d, where K is the tightening coefficient 0.15 - 0.2, P is the axial force, and d is the thread diameter).
3. Cooling and gap recheck
After installation, allow the bearing to cool to room temperature naturally, measure the radial runout of the bearing with a dial indicator (≤ 0.05mm), the axial clearance needs to meet the standard (for a 100mm inner diameter self-aligning roller bearing, the clearance C3 group is 0.100mm - 0.150mm), if the clearance is too small, check if the interference fit is too large.
3.1 Cold installation process for clearance fit bearings
1.1 Direct pressing or lubrication installation
Pressing tools: Use a socket (matching the inner ring diameter) through a hydraulic press for pressing, the pressure needs to be evenly distributed on the inner ring, avoid tilting (pressing speed ≤ 2mm/s). Lubrication assistance: If the fit is tight, a thin layer of oil (with a viscosity of 32 cSt) can be applied to the shaft neck surface to reduce the installation resistance. However, be careful not to use too much oil to avoid overheating during operation.
2. Axial fixation and clearance adjustment
When the outer ring is in clearance fit with the seat hole, the axial position needs to be fixed through end caps, snap rings, etc. The clearance is adjusted by using spacers (for example, if the target clearance is 0.12mm and the measured clearance is 0.08mm, an additional 0.04mm spacer needs to be installed).
IV. Post-installation inspection and trial operation
1. Accuracy inspection
Radial runout: Fix the shaft, place the dial indicator probe against the outer ring surface, rotate the shaft for one revolution, and the runout value should be ≤ 0.03mm (for high-precision bearings, ≤ 0.01mm).
Axial clearance: Use the dial indicator to press against the shaft end, push and pull the shaft to measure the axial displacement, and the clearance value should comply with the standard of the bearing model (refer to GB/T 4604.1).
2. Lubrication and trial operation
Replenishing oil: If the lubricating oil is lost during installation, it needs to be replenished through the oil injection hole (the replenishment amount is 1/3 - 1/2 of the volume of the bearing cavity, excessive replenishment will cause overheating).
No-load trial operation:
Run at low speed (300r/min) for 10 minutes, check the temperature rise (≤ 30℃), noise (≤ 65dB), and if there are no abnormalities, gradually increase to the rated speed.
If abnormal vibration is found (such as the frequency being a multiple of the rolling element passing frequency), the machine needs to be stopped for inspection of the installation coaxiality (≤ 0.05mm/m) or the interference fit.