Technology knowledge

Structural design of a specialized puller for destructive disassembly of deep groove ball bearings

Bearings are common components in machines. Bearing disassembly is a common task in machine maintenance. Due to the wide variety and specifications of bearings, the dismantling tools used for bearings are also different. Due to the need for dismantling work, maintenance personnel have also designed various dismantling pullers, such as ordinary three jaw pullers and specialized pullers for dismantling bearings with snap ring grooves. Due to the large size of the claw, the three claw puller needs to occupy a large space during disassembly, so its use is limited by the space conditions of machine installation. Some machines have bearings that cannot be pulled out by ordinary pullers due to limited space. Some bearings are difficult to disassemble due to corrosion, damage, and other reasons. Considering that many bearings in bearing maintenance will be replaced with new ones after disassembly, and the dismantled bearings will no longer be used. This article designs a puller for the destructive disassembly of deep groove ball bearings.

1. Question raising

Due to the needs of machine function and structure, various structures have emerged for the installation of bearings in machines. Due to functional requirements, bearings also have different choices in installation positioning and fitting properties. If the fit is tight and the installation space is narrow, the difficulty of disassembly will increase. If the bearing rusts due to other reasons, disassembly will be more difficult. As shown in Figure 1, on the right side of the bearing is the gear, and the space between the gear and the bearing is relatively small. The outer ring of the bearing and the bearing seat hole are fitted with an interference fit. Only after pulling out the bearing can the gear shaft be taken out from the left side. If there is rust on the outer ring and seat hole of the bearing during maintenance, it will become more difficult to remove the bearing and gear shaft. There is not enough space to detach the bearing from the bearing seat by tapping the outer ring of the bearing from the right side, so it can only be considered to remove the bearing from the left side. Some people may consider using the force of flame heating to heat the bearing seat hole and remove the bearing and shaft, but this will cause deformation of the seat hole, which will affect the function of the repaired machine. In this case, using a special puller for deep groove ball bearings can easily remove the bearings.


Figure 1 Installation position of bearings

2. Structural design of specialized pullers for destructive disassembly of deep groove ball bearings

2.1 Dimensions and disassembly bolt rod design of deep groove ball bearings

Deep groove ball bearings consist of an outer ring, an inner ring, a rolling element, and a retaining structure. There are circular groove shaped raceways with rolling elements installed on the inner and outer sides of the outer ring, and the rolling elements roll within the raceways, as shown in Figure 2. The diameter Dw of the rolling element, the inner diameter D2 of the bearing outer ring, and the outer diameter d2 of the bearing inner ring can be found in the relevant manuals of mechanical design. The gap width H between the inner and outer rings of the bearing can be determined by calculation. The size is H=(D2-d2)/2. When designing the puller, consideration is given to the rolling element rolling between the inner and outer raceways without falling off because the rolling element has a suitable size and distribution. Design a disassembly bolt with a head that is similar in size to the rolling element. The rolling element needs to be cut off in part, as shown in Figure 3. When disassembling, use a screwdriver to impact and damage some of the retainer. Insert the disassembly bolt head into the gap between the inner and outer rings, and then rotate 90 ° to insert the disassembly screw ball head into the inner and outer raceways, as shown in Figure 4. Connect another striker to its end, and through the sliding impact of the striker to the left, generate a left pulling force to pull out the bearing.


Figure 2 Structure and dimensions of deep groove ball bearings


Figure 3 Structure of disassembling bolt heads


Figure 4: Disassembling the bolts and installing them into the inner and outer raceways

The design of dismantling bolts Z is crucial in the design of pullers. If the head size is too large, the disassembly of the pull rod head cannot insert the ball head into the raceway between the inner and outer rings through the gap between the inner and outer rings, and cannot achieve the integration of the ball head and the inner and outer rings. If the head size is too small and detaches from the inner and outer rings, the ball head cannot fit with the inner and outer rings, cannot pull the inner and outer rings together, and cannot pull out the bearing. Therefore, it is necessary to correctly determine the structure and size of the bolt head for disassembly.

As shown in Figure 5, the structure and dimensions of the disassembled bolt head must be related to the bearing size. In the figure, Dw represents the diameter of the steel ball to be removed from the bearing, and H represents the gap width between the inner and outer rings of the removed bearing. A is the diameter of the connecting rod between the ball head and the threaded part, which should be less than or equal to H. Considering the convenience of installing the disassembly bolt head into the bearing during disassembly, the upper and lower deviations of Dw dimension in Figure 5 can be designed as negative values. The correct size is necessary to ensure that the disassembled bolts can be correctly installed between the inner and outer rings of the bearing, and the bolts will not detach during disassembly.


Figure 5 Structure and dimensions of bolt head disassembly

2.2 Structural design of pullers

To pull out the bearing, a striker should also be connected at the end of the bolt for disassembly, as shown in Figure 6. Disassemble the bolt and connect the connecting nut through a threaded connection, install a hammer on the sliding rod, and then connect the sliding rod with the connecting nut to assemble it into a combination puller. When disassembling, first damage and remove the retaining bracket of the bearing to be disassembled, leaving space for the disassembly bolt to be placed in the inner and outer raceways. Then, place the disassembly bolt in the inner and outer raceways of the bearing and rotate it 90 °. Use force to slide the hammer and generate tension to pull out both the inner and outer rings of the bearing simultaneously. In order to disassemble bearings of various sizes, different sizes of disassembly bolts can be machined according to different bearing sizes. To achieve the serialization of puller products and meet the needs of maintenance. Of course, if dismantling larger bearings or bearings with severe rust, a larger hammer is required, otherwise there is not enough tension to pull out the bearings.


Figure 6 Destructive disassembly saw for deep groove ball bearings

3. Conclusion

Deep groove ball bearings are widely used in machines, and bearing replacement during maintenance is very common. For some machines, due to structural limitations, ordinary pullers cannot be used to remove bearings, and most of the removed bearings are no longer in use during maintenance. Damaging old bearings will not increase maintenance costs. This makes destructive removal of bearings a maintenance option, and using this destructive removal puller can facilitate and quickly remove such bearings. Provide convenience for machine maintenance and greatly improve maintenance efficiency.

2024 May 2th Week JFZ Product Recommendation:

Deep groove ball bearing 6200 Series:

6200 series bearing is deep groove ball bearing, mainly used in centrifuges, half-shaft bolts, CNC punches, cylindrical gear reducers, electric vehicle motors, pressure reducing valves, CNC cutting, electrodialysis equipment, electrical instruments, and automotive lights etc.

The product we provide is of medium and high quality. Please feel free to discuss your specific needs at any time.