Assembly of ball bushings
The installation of ball bushings is generally not complicated, on the contrary, it is fortunately relatively easy to carry out. There is therefore not a great deal to consider during assembly: It is only important to take the installation tolerances and ambient conditions into account. You can find detailed information on this as well as installation instructions in this article.
Assembly tolerances
In connection with the assembly of ball bushings, a few tolerances must be considered, which firstly depend on the type of ball bushing, i.e. ISO, JIS, super ball bushings and ball sleeves. The tolerances relate to the shaft diameter on the one hand and the housing bore diameter on the other.
Although there are various recommendations for the shaft diameter, an h6 shaft is recommended in most cases: To be precise, this is the standard recommendation for JIS and super ball bushings as well as for ball sleeves, while the h6 shaft is generally used for ISO ball bushings in applications with little or no clearance.
With regard to the housing bore diameter, i.e. the housing into which the ball bushing itself is mounted, an H7 bore can be named as the classic tolerance for a clearance fit. In applications with reduced clearance, a bore of size J7 is recommended.
Bending of the shafts
If long steel shafts are used as self-supporting shafts with closed ball bushings or if a shaft is subjected to too much load, there is a risk of bending of the steel shafts. As soon as these bending exceed permissible limits, reliable function can no longer be guaranteed as high peak loads occur at the ends of the ball bushings. On the one hand, the ball bushing then runs unevenly, and, on the other hand, the service life is significantly reduced. To counteract this tendency, there is a variant of the super ball bushings with tolerance compensation, which are able to compensate for angular errors of up to ±0,5°.
Assembly instructions
For mounting cylindrical ball bushings in housings, we recommend using an auxiliary tool that is adapted to the diameter of the ball bushing. This tool is required to carefully push the bushing into the housing. It is particularly important to note that only suitable auxiliary tools may be used.
If flanged ball bushings are to be fitted, it must also be ensured that they are carefully inserted into the housing. The ball bushing must only be fastened with the reference surface to the housing. This means that it is essential to ensure the correct installation direction: If it is installed the wrong way round, there is a risk of a bending moment acting on the ball bushing, which in turn can cause the flange on the ball bushing to break off, for example. If you want to install ball bushings in the unusual direction, this is possible with so-called reversing flange bushings; however, these are very rare on the market and are only used in specific applications.
It is also important to pay attention to a few basic aspects when installing ball bushings on the shafts. Firstly, only deburred shafts may be used. Ball bushings must be carefully pushed onto the shaft and should not tilt. If parallel shafts are used, they must be aligned so that there are no misalignments between the two shafts.
Product selection
To round off this article, here are a few words on product selection, which is important in order to configure the right product for the installation. Of particular importance here are the criteria of installation space, mounting options and environmental conditions, which must always be considered in this context. The exact conditions involved can be seen in the table.
| Installation space | Mounting options | Environmental conditions |
• Possible system height • Possible system width • Number of parallel shafts • Number of ball bushings per shaft • Accessibility for maintenance | of the shaft: • Self-supporting, with shaft supports or with traverses • With support rails of the ball bushings: • Cylindrical ball bushing in a housing • Mounting via flange | • In case of pollution: Use ball bushings with a suitable sealing system • If aggressive substances: Use corrosion-resistant versions • If there are special environmental conditions, e.g. clean room: Selection of the optimal configuration (lubricants, seals) |
With regard to installation space, mounting options and ambient conditions, there are a few things to consider when selecting a product.
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