Plain bearings for sheet metal – how to avoid errors and damage

Lars Butenschön | 24. April 2020

Normally, plain bearings are intended for installation in relatively thick-walled designs. The plain bearing is pressed into a hole of recommended tolerance, where it remains. Press-fit can be difficult if the components have thin walls. But beyond fixing in place, there are other pitfalls which we will examine more closely here. Then I will give you a few tips on how to choose the right plain bearings for sheet metal.

Clean (or at least deburred) edges

Before considering the plain bearing shape, we should take a look at the hole. Thin-walled metal sheets frequently cost little to machine. The primary problem for plain bearing solutions here is poor fixing holes. For instance, these holes are usually punched or lasered without further machining. The primary result is sharp edges, and for punched holes, very wide tolerances. This is not ideal, especially for plain bearings made of polymer. Chamfer these edges slightly, or at least deburr them. If this proves unmanageable, free the holes of burrs and projecting material. It is very difficult to change tolerances without re-drilling. The process is simply too expensive with many sheet metal constructions. Because manufacturing tolerances are primarily responsible for the press-fit of the plain bearing, we can get around the problem by choosing the right shape.

Fixing the plain bearing securely

If we do not have an H7 tolerance in our sheet metal, things get difficult. If covers are not big enough to enclose the hole and bearing, the bearing will not remain securely in the hole. Without additional positive locking, the bearing will “move” slowly out of the hole. The danger is that the shaft will run directly in the hole without a protective bearing. The positive fit can be achieved with undercuts. You can use flanges to screw the plain bearing directly into the surrounding construction. Screw connections take additional time to install, and flanged bushings commonly used to keep them from falling out only work in one direction. Two flanged bushings are better. But how is the bearing to be fixed in the hole? There are slotted designs with multiple undercuts. They can be pressed together during assembly. After the assembly is in the hole, the second undercut slides behind the metal sheet, securing the bearing.

Consider other environmental parameters

Plain bearings for sheet metal must often meet other requirements as well. Things get really interesting when the sheet metal construction comes into contact with food, is subject to high temperatures, or must be dip-coated, as is common in the car industry. The concern then is not so much the component shape, but the selection of the right material. Here, polymer bearings can be a good alternative to metallic ones. They are not only corrosion-free, but depending on the application, they require no lubrication. The various options for processing plastics to form multifaceted or specialised compounds or mixtures can produce materials that can withstand such special conditions.

Why complicate things if they can be simple? Off-the-shelf solutions

iglidur M250 clip bearings can be clipped easily into sheet metal. Press it together, push it through, and that’s all there is to it. Their shape and flexibility make these plain bearings ideally suited to sheet metal. They are injection moulded from iglidur M250 and are a cost-effective alternative to metallic plain bearings.

Clip bearings made of iglidur A230, on the other hand, are especially well suited to applications in the food industry. The material conforms to both FDA regulations and EU10/2011 and can be used in contact with food. It is also flexible and dimensionally stable.

Temperature and chemical-resistant, iglidur K250 is a good choice for the applications outlined above in motor vehicles or with furniture and other consumer goods that must be painted in immersion baths.

In the video, Stefan Loockmann-Rittich, Head of the igus Plain Bearings Business Unit, presents iglidur clip bearings for sheet metal.

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Are you having problems with your sheet metal solutions? Or do you need help designing your plain bearing application? We would be happy to advise you! Free of charge and without obligation, digitally or by telephone.