Gluing bushings – this is how it works
Lars Butenschön | 25. February 2022
Bushings are usually pressed or clamped into the housing hole. In this way they hold securely in the hole and do not rotate unintentionally. But what if this is not possible due to manufacturing tolerances? Another not so rare case: The bushing should even rotate. Even if it is not part of the standard repertoire of many bushings – plastic plain bushings can also slide on the outer diameter. Many a machine builder therefore resorts to bushings made of plastic. The bearing is placed on a bolt and should then – together with the bolt – turn in or roll on something. Then the question also quickly arises: “How do I get this to hold?” In these cases, the said machine builder often ends up with bonding as the most suitable solution.
Bonding plastic bushings – with the right adhesive
There are many adhesives for bonding plastics. The problem: Plain bearings are often not made of “simple” plastics, but of plastic compounds or plastic blends. These are mixtures of plastic-polymers and additives and fillers that complement their properties. Materials that improve the sliding properties, such as silicones, MOS2 or PTFE, can be particularly problematic here. In these cases, you should seek advice directly from the manufacturer of the bushings.
In reality, however, these ingredients have different effects. In most cases, even with these ingredients you can handle them quite well with special adhesives. We at igus® have had good experiences especially with two-component adhesives, e.g. the combination of Loctite 406 and Loctite 770 Primer. For plain bearings made of plastics with lower proportions of substances to improve the sliding properties, Loctite 401 without primer also offers good results. Of course, comparable adhesives from other manufacturers can also provide potentially good results.
Important: Prepare surfaces of bushings to be bonded well
As in many life situations, the same applies to the bonding of plastic plain bearings: preparation is everything. To make sure that in the end everything holds well, you should consider the following:
- Clean the surfaces to be bonded to remove dirt, rust and other foreign matter
- Roughen the surfaces slightly by grinding
- Degrease the adhesive surfaces thoroughly, e.g. with alcohol, nitro thinner or acetone
- Let the glued areas dry well afterwards
We would be happy to assist you!
Gluing in bushings is often not the ideal form of bushing assembly. Especially with moderate quantities, the additional assembly work represents a substantial cost factor. Often even small changes to component tolerances or component geometry can make bonding superfluous.
But even if there is no way around gluing – we not only advise you on possible alternatives to gluing, but also on the best design and execution of glued joints for plain bearings if the situation warrants it.