With a global impact of approximately $26 billion, portable power tools are an essential tool for residential, industrial and commercial applications. Therefore, it is important to recognize the role that ball bearings play in your performance; withstand combined load conditions and high-speed operation; allowing low friction, low noise and low vibration; and ensuring reliability. Below is a summary of the most important considerations when specifying or selecting ball bearings for portable power tools.
Bearing Loads : Ball bearings are an ideal component for power tools. They simultaneously support radial and axial loads. If axial loads are excessive, supplement radial ball bearings with thrust bearings to effectively support these loads.
Noise and vibrations : When power tools emit noise and vibration, they directly impact the operator and cause fatigue and general dissatisfaction with the tool. Several factors may be at play, including bearing quality, poor tool design, or poor process control during tool manufacturing and assembly.
Bearings with poor geometry rings tend to emit lower frequency noise and vibration, while balls or races with poor surface finish tend to emit higher frequency noise and vibration. We recommend using bearings manufactured to Electric Motor Quality (EMQ) noise levels, which indicate their suitability for use in electric motors.
To minimize noise and vibration, power tool manufacturers must specify and properly apply preload to bearings. The application of axial preload forces the balls into contact with the races, establishing a contact angle that rotates the ball assembly in a uniform circumferential plane. Preload is critical in high-precision, high-speed power tool applications where speeds can reach 60,000 rpm.
Operating temperature : To minimize the operating temperature of power tools, manufacturers must mount bearings correctly, having the appropriate preload and type of lubrication.
Bearing materials : To optimize performance, bearings must be manufactured from high quality materials. Bearing rings and balls are commonly manufactured from SAE 52100 chromolytic steel, which offers excellent resistance to fatigue and wear. If there is a risk of exposure to moisture, martensitic stainless steel should be used.
Ceramic balls offer additional high-speed benefits, although they are not generally used in portable power tools.
Lubrication : Designers and engineers often overlook the importance of lubrication to the performance and life of ball bearings.
Typically, bearings found in small power tools are lubricated once during the life of the device. Operating temperature is the primary consideration when selecting a lubricant, as temperature directly affects the viscosity of the base oil, which in turn affects its load-bearing ability.
Harsh environments : When power tools are continually exposed to liquids or debris, consider using gaskets or guards to protect the bearing.
Nitrile rubber is a common material for bearing seals, which provides protection against contamination but reduces the maximum speed capability of the bearing. This is a design compromise that favors durability.
With numerous variables and factors affecting the performance of bearings in portable tools, we recommend consulting a bearing applications expert who can assist you in calculating load capacity, bearing life, component fits and tolerances.
