What is an interference fit for oil-free bearings?

The interference fit of oil-free bearings means that during the installation process of oil-free bearings, the outer diameter is designed to be slightly larger than the inner diameter of the seat hole, which generates a certain amount of stress after assembly. This design aims to maintain a high roundness of the inner circle of the bearing and secure the bearing more firmly, effectively preventing slippage and wear. The design and application of oil-free bearing interference ensures the stability and reliability of the bearings under harsh working conditions.

‌Advantages of interference fit

• Sturdy connection‌: Interference fit can ensure that the connection part is very strong and has a high degree of tightening.
• Simplified structure‌: It reduces the number of required parts and helps simplify the overall structure of the machine.
• Withstand impact‌: This type of fit is particularly suitable for withstanding impact loads and connections that do not often need to be disassembled.

Oil-free bearings, such as the SF-1 series, have significant features such as no need for lubrication, easy maintenance, and long service life. Therefore, they are widely used in various types of mechanical equipment, especially in situations with low speed, heavy load or difficult maintenance.

‌Calculation of interference

The interference is divided into minimum and maximum values, which are calculated from the maximum and minimum values of the outer diameter of the bearing and the inner diameter of the seat hole.
The calculation formula for interference is as follows:

• Minimum value of interference δmin = minimum value of bearing outer diameter Dmin - maximum value of seat hole inner diameter 
• DHmax
  Maximum interference value δmax = Maximum value of bearing outer diameter Dmax - Minimum value of seat hole inner diameter DHmin

Example:
SF-1 series SF-1·2015 (standard product), matching seat hole Dh=23H7+0.021, find the interference amount after assembly.
Calculate:
It is known that the maximum bearing outer diameter Max=23.075 and the minimum bearing outer diameter Min=23.035;
The maximum value of the inner diameter of the seat hole is Max=23.021, and the minimum value of the inner diameter of the seat hole is Min=23.00.
δmin=minimum bearing outer diameter Dmin-maximum seat hole inner diameter DHmax=23.035-23.021=0.014
δmax=maximum bearing outer diameter Dmax-minimum seat hole inner diameter DHmin=23.075-23.000=0.075
Therefore, the interference amount after assembly δ=0.014~0.075mm

The following points need to be noted for the interference fit of oil-free bearings:

• Control the interference amount‌: The interference amount should be strictly controlled between 0.1% and 0.5% of the bearing inner diameter and the shaft outer diameter, and the influence of internal thermal expansion that may occur during operation must be considered, so a margin of more than 0.01mm must be reserved. quantity.
• Prevent from being too loose or too tight‌: Too loose may cause the balls to deflect and affect bearing performance; while too tight may cause the bearing to heat up, weld the balls to the track, and even cause damage to the bearing.
• Ensure cleanliness‌: Before installation, make sure the bearing and shaft hole are clean and free of debris, and thoroughly remove oil and rust.
• Use special tools‌: Special tools should be used for installation to ensure the quality and accuracy of the installation and avoid damage caused by using improper tools.
• Check the installation quality‌: After the installation is completed, key parameters such as the bearing inner diameter, shaft hole size and interference amount should be carefully checked to ensure that the installation quality meets the relevant requirements.

In addition, attention should also be paid to the inspection of interference fitting parts before assembly, such as interference amount, verticality deviation, mating surface condition, etc., to ensure smooth assembly and normal use of the bearing.