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Installation of rolling bearings – Heating installation method. When the inner diameter of the bearing is greater than 70 mm, or when there is a large degree of interference, the heating method is used to expand the bearing hole. This makes the installation process easier and faster, and it also prevents damage caused by excessive force. What needs to be controlled at this time is the heating temperature; generally, it is sufficient to heat the bearing to 80°C, with a maximum of 100°C. Tempering of the bearing occurs above 120°C, resulting in a decrease in the hardness and precision of the rings. Common heating methods include: 1. Electric heating plate method – Place the bearing on an electric heating plate set at 100°C for a few minutes; this is the simplest method. Turning the bearing several times ensures even heating, and it is also efficient. This method can be used for bearings of various sizes. 2. Electric furnace heating method: The bearings are placed in a closed, automatically temperature-controlled electric furnace for heating. This method ensures uniform heating, precise temperature control, and fast heating speeds, making it suitable for heating a large number of bearings at once. 3 Induction heating method: An induction heater can be used to heat the bearing to the desired temperature quickly, reliably, and cleanly. This method is particularly suitable for situations where there is a tight fit on the inner ring; since only the inner ring is heated while the outer ring receives little heat, it is easier to install the bearing on the shaft as well as in the housing bore. 4. Bulb heating method: A 50W light bulb is used to heat the bearings, ensuring a heating temperature of around 100°C. Smaller bearings can be placed directly on the bulb, while larger bearings can be placed inside the bulb’s conical cover; this cover helps prevent heat loss from the bulb and ensures even heating. The conical cover can be adjusted up and down, allowing it to accommodate bearings of different sizes within a certain range. If far-infrared bulbs are used, make sure the bulbs are directed downward to prevent the infrared rays from being harmful to human eyes. This type of light bulb can save energy. The bulb heating method is suitable for small quantities that are not frequently needed ； In cases where the bearing needs to be heated, the light bulb can also be used for lighting; no other equipment is required. 5 Oil tank heating method: This is a traditional heating method that is widely used. A metal mesh is placed at a distance of 50–70 mm from the bottom of the oil tank; the bearings are placed on this mesh, and larger bearings need to be lifted using hooks. Bearings should not be placed directly on the bottom of the groove, to prevent the parts of the bearings in contact with the bottom from overheating, or to stop dirt accumulated at the bottom of the groove from getting into the bearings. The key points to note for the oil tank heating method are as follows: non-corrosive mineral oil with good thermal stability should be used, preferably transformer oil; both the oil and the container must be kept clean. The capacity of the oil tank should be determined by the size of the bearing to be heated and the amount of oil required. If the container is too small, the oil temperature will drop rapidly during continuous operation once the bearing is placed in it, resulting in poor performance. Key points of the heating installation method: ① The heating temperature must be controlled properly; too high a temperature can damage the bearings, while too low a temperature results in insufficient expansion of the rings, leading to inadequate effects. The thermal expansion amount of the inner ring inner diameter at heating temperatures of 80–1000°C is sufficient for bearings with a normal interference fit. ②Once the desired heating temperature is reached, installation should be carried out as soon as possible to avoid difficulties in installation due to cooling. ③The bearing also contracts in the width direction during cooling; therefore, a certain amount of pressure must be applied during installation to press the inner ring against the shoulder. After cooling, a very thin feeler gauge is used to check whether there is any gap between the end face of the inner ring and the shaft shoulder. In short, butterfly folding requires skill, speed, and accuracy.