How to secure bearings properly – Part 2: axial securing
Lars Butenschön | 27. November 2018
In part one of my series “How to secure bearings properly”, we learned how and why bearings move in their mounting holes and what we can do against it. If press-fit is not enough or not available in order to keep a bearing in place, you can do so by changing it´s shape. In this post we want to take a look at different ways of axial securing bearings.
Option 1: Axial securing bearings with slit bearings and undercuts
With the open slit design, a bearing can compensate for a certain range of tolerance deviation of the housing bore. At the same time, this design allows for a double flanged shape. The two flanges allow for axial securing in both directions. With the slit design, the bearing can be compressed, allowing the second flange to be put through the mounting hole. Once put in, the bearing expands again so the second flange can keep the bearing from falling out of the housing. As you can imagine, this design also requires a certain flexibility of the bearing material.
Option 2: Axial securing bearings with “Snap in” solutions
Snap features can also help securing bearings axially. During assembly, the protruding undercut features are pressed together automatically. As soon as they pass the assembly hole, they “snap” back in place and keep the bearing from going back. The flange at the back end of the bearing further prevents the bearing from going in too far. An easy process which is reliable and fast. Ideal for mass production.
Option 3: Axial securing bearings with flexible double flange bearings
A more advanced way of mounting double flange bearings and mainly used in the automotive industry: Flexible double flanged bearings. These bearings offer a special flexible flange. Initially, the bearing only has a flange on one side. The opposite side consists of a number of radially placed slits. After the bearing is pushed through the mounting hole, another pushing device applies pressure from the opposite side of the mounting hole. During this process, the slit features bend outwards forming a flange. The bearing sits tightly secured in the mounting hole.
Option 4: Axial securing “bullet proof” using screws. mit Schrauben und mehrteilige Lösungen
If everything else fails: A flange with holes for screws. Just put some screws in after the assembly of the bearing and don´t worry anymore. It´s not really practical for automated assembly but it get´s the job done.
Almost free design choices with plastic bearings
Plastics offer almost limitless design potential. They can be molded or bent into almost any shape and are easy to cut and machine. Using modern production technologies like 3D-printing, laser sintering or injection molding, it´s easier than ever to make ideas a reality. Of course, metal bearings can also be made in many different shapes. However, the processes involved are often considerably more expensive and their design is limited by the necessity of lubrication (either by solid but thin layers or by liquid lubrication).
Plastics, especially tribologically optimized ones (means: optimized for low wear and friction) offer a homogenous structure. They are comprised of a mixture of solid lubricant particles, additives and polymers. Therefore, every surface of a plastic bearing can serve as sliding area.
Of course, you can also combine the options above to avoid a bearing turning in it´s housing. Why that can be useful and which options can be used as anti-rotation features, watch out for part 3 of this post series.