For a long time, motor repair personnel have only focused on the electrical parts (mainly the windings) and neglected the installation process of the mechanical parts (mainly the rolling bearings).
In recent years, the market has seen a surge in substandard rolling bearings, leading to a significant increase in mechanical failures. Repairing mechanical failures primarily involves replacing and installing rolling bearings. Traditional motor textbooks describe using a hammer and iron bar to impact the inner sleeve of the rolling bearing during installation. However, in practice, this method is labor-intensive and can easily injure repair personnel, often damaging the bearing. Because the impact force on the inner sleeve is uneven, it can easily break or deform, accelerating the wear of the balls and rollers between the inner and outer sleeves, causing premature bearing failure and motor stator rubbing. It also frequently damages or dislodges the fully sealed or semi-sealed grease retainers (currently, motors primarily use fully sealed rolling bearings). During operation, the grease, under pressure and temperature, can overflow onto the windings, especially under high-speed, heavy-load, and high-temperature conditions. These problems can ultimately lead to motor burnout due to stator rubbing or excessively dirty windings, disrupting production and causing economic losses. Therefore, the installation of rolling bearings cannot be ignored, and the installation process must be improved.
Rolling bearings used in motors are classified into fully sealed, semi-sealed, and unsealed types, with fully sealed bearings being the most common. Commonly used models in power tool motors include 608, 629, 200, 201, 202, and 203; in household micro-motors, models include 608, 629, 200, 201, 202, 203, 204, and 205; in automotive motors, models include 201, 202, 203, 204, 303, and 304; and in single-phase and three-phase small and medium-sized motors, models include 203, 204, 205, 208, 303, 304, 305, 306, 308, and 309. The external shape of the "bearing punch" (special tool) machined by the author is shown in Figure 1. The machining dimensions are shown in Table 1. When installing bearings, a thin layer of grease can be applied to the inner sleeve. Then, strike the non-open end of the bearing punch with a hammer. The large contact area between the end face of the bearing punch and the end face of the bearing inner sleeve ensures even force distribution, making installation labor-saving, safer for the operator, and preventing damage to the bearing. After several years of practical use, this method can improve work efficiency several times over and ensure the service life of bearings and motors.
(Figure 1) Outline drawing of bearing punch (special tool)
(Table 1) Machining Dimensions of Bearing Punch
In summary, rolling bearings are relatively precision components, and only proper installation can guarantee their service life. The bearing punch introduced in this article is simple to process and easy to use, and can improve work efficiency several times over. It is suitable not only for the installation of rolling bearings in electric motors but also for rolling bearings in other equipment. We encourage our colleagues to try it out and provide valuable feedback.
