The Precision and Quality of Bearing Components are Critical Characteristics Regardless of the Application.
By Anthony Romero – Sales and Applications Engineering Manager
George Rusiecki of the former Torrington Co. described drawn-cup needle roller bearings (NRB) this way:
“For ease of handling and installation, drawn-cup needle roller bearings do as well as loose rollers but in a unitized assembly. The outer shell, which serves as the outer raceway, is accurately drawn from low-carbon strip steel and case hardened. No subsequent machining is needed, making this bearing economical. The turned-in lips of the cup provide mechanical retention of a full complement of trunnion-end needle rollers. Also, these lips act as close-fitting shields and help retain lubricant and exclude foreign matter.
Full-complement drawn-cup needle bearing load ratings equal or exceed those of ball and roller bearings of comparable OD. Thin cross sections allow larger shaft diameters on which the bearings operate directly. The large number of contact lines formed by the loaded rollers suits this type well for static, slow rotating, or oscillating conditions. Drawn-cup caged bearings share many characteristics with their full-complement counterparts, such as being well suited for use in housings of low hardness. Though they have less load capacity than full-complement bearings, they are better suited for high speed and shaft misalignment or load deflection.” 
The Use of Deep Drawn Bearing Components
The quality and precision of drawn-cup needle roller bearings are critically important, especially when they are used in automotive deep draw applications such as engines, pulley supports, gear pumps, planetary gears, or transmissions. Paying less for lower-cost bearings can seem like a good cost-saving measure. However, when you consider the labor costs charged by auto mechanics and dealerships to replace NRBs, those savings quickly disappear.
In industrial uses, faulty NRBs can affect the reliability of equipment and cause machine downtime and production losses. Additionally, it is easy to imagine the negative impact on customer loyalty when there is a premature bearing failure in consumer goods like washing machines, lawn mowers, snow throwers, and similar products.
Unfortunately, some offshore factories frequently leverage a higher quantity to make a profit when manufacturing these bearings. With rising material and labor costs in the global market, these providers keep prices low by using cheaper materials, performing low-precision manufacturing, and doing a poor job of inspecting finished parts.
As explained in our blog titled “The importance of raw material quality in the deep draw metal process” defects in materials adversely impact the service life of parts. In the case of NRBs, using low-quality materials affects the load stresses on the raceway. Since any tears, porosity, or inclusions in the raw material can hinder the integrity of the bearing causing a premature failure.
The uniformity of the wall thickness on the drawn cup is another characteristic that plays an important role in maintaining a uniform loading profile on the bearing. At Prospect Machine Products, special inspection procedures are used to ensure that this characteristic is maintained within print specifications.
The same is true of the taper of the cup, since it is also involved in the loading of the rollers. Additionally, the surface finish of the actual internal raceway is crucial to the life expectancy of the bearing due to the thin oil film thickness between the raceway and needle rollers during operation.
Ultimately, there are many characteristics of drawn-cup needle roller bearings that can lead to premature failure when inadequate materials, forming processes, or inspection procedures are used. Buying low-priced bearing components can definitely come back to haunt you!
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 Machine Design – Needle roller bearings: what they are; where they go; why you may need them. George Rusiecki of the Torrington Co. | Jun 01, 2000