Both ball and needle retainers can be made in metal or plastic. The decision to choose the appropriate material is based on a few factors. The first factor is the operating condition or environment in which the retainer will function.
If the thrust bearing and retainer must operate in extreme heat, corrosion, or high abrasiveness, then the decision will most often be to use metal. Different metals will be selected such as carbon steel, stainless steel or even brass or bronze.
Plastic retainers used where corrosion resistance is important. Also, plastic is used when the part needs to be light-weight. In these applications the operating temperatures are usually close to the ambient temperature.
The second consideration is cost. Often this becomes a function of volume. Both metal and plastic retainers require a certain amount of tooling to manufacture. With metal retainers, you can do single station tooling. Also, low volume tends to be more cost effective in metal. Additionally there are several ways of controlling the tooling costs in high volume runs for metal retainers.
Typically in ball retainers, the decision to go with plastic versus metal is the same. However, in high volumes, plastic tends to be a little lower in overall cost. In needle bearings, plastic is significantly less expensive than metal but there is a design trade-off. In metal needle bearings you can get the needles closer together to carry more load. If the needle bearings are constructed in plastic, the needles have to be spread out and carry less of a load, but the plastic bearings will be cheaper.
National Bearings analyzes each bearing application carefully and presents the options to ensure the highest quality and cost considerations. The facility is fully equipped to produce bearings in different materials in low or high volume runs and offer complete tooling for the application.