Slewing rings and turntable bearings can accommodate axial, radial and moment loads. They are not housed or mounted on a shaft, but are instead mounted directly to a seating surface. The inner and outer rings are supplied with mounting holes and often include internal or external gears. There are several basic types of products. Single-row slewing rings and turntable bearings feature a single row of balls, a standard bearing raceway, and four points of contact between the balls and raceway. Double-row products feature two rows of ball bearings, two raceways, and eight points of contacts for each ball. Slewing rings and turntable rings with three independent rows of rollers are also available. Cross rollers have a single row of rollers with the axes of alternating, adjacent rollers at right angles to one another. Slewing rings and turntable bearings with a single row of balls and a single row of rollers are designed for small radial runout and high thrust roads. Typically, inserted raceways are made of wire and use either a ball or roller as the contact element.
Dimensions and Specifications
Slewing rings and turntable bearings vary in terms of physical dimensions and operating specifications. Bore size, outside diameter and overall width are the most important physical dimensions to consider. Metric bores are measured in millimeters (mm) and specified according to a standard numbering system that ranges from 00 (10 mm) to 20 (100 mm). Bore sizes 00, 01, 02, and 03 are 10 mm, 12 mm, 15 mm, and 17 mm, respectively. For bore sizes 04 and up, multiplying the bore size by 5 yields the bore diameter. Slewing rings and turntable bearings that are measured in inches (in) or fractions of an inch are also available. For flanged bearings, the outside diameter excludes the size of the flange. Overall width includes the size of the locking collar, if present. In terms of operating specifications, the most important measurements to consider are static axial or thrust load, static radial load, and moment load. Typically, these specifications are measured in pounds (lbs) or feet-pounds (ft-lbs).
There are many applications for slewing rings and turntable bearings. Some products are suitable for foundry shakeout tables, palletizers, wire winders, cable reels, welding tables and turntable applications with intermittent rotation and low velocity. Others are used with hoists, truck-mounted cranes, and industrial tables and positioners. High-performance slewing rings and turntable bearings combine constant repeatability with precise positioning and stopping. Slewing rings and turntable bearings for worm drive rotation systems are also available.
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