Slewing Rings and Turntable Bearings Information
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.
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.
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.
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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.
Outside diameter and overall width are also important physical dimensions to consider. 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).
SAE PAPER 831371 -- Case depth for induction hardened slewing bearing rings.
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Cylindrical Roller Bearings
Cylindrical roller bearings have high radial-load capacity and moderate thrust loads. They contain rollers which are cylindrically-shaped, but crowned or end-relieved to reduce stress concentrations.
Radial Ball Bearings
Radial ball bearings are friction reduction, rotation devices that carry loads radially around its axis. A subtype of ball bearings, they operate through the use of lubricated steel balls placed between two circular guides. They are frequently called deep-groove bearings.
Spherical Roller Bearings
Spherical roller bearings are self-aligning bearings ideal for heavy-duty radial and axial loads. They utilize dual roller rows between a concave outer raceway and convex inner raceway to accommodate shaft deflection.
Super Precision and Spindle Bearings
Super precision and spindle bearings are high-precision bearings that are designed for use in machine-tool spindles and other precision applications. Most super precision bearings and spindle bearings carry a high quality-rating such as ABEC-7 or ABEC-9, and run coolly and smoothly at high speeds.
Tapered Roller Bearings
Tapered roller bearings use rollers with different-sized diameters on each end. The rollers and accompanying bearing components can accomodate axial and radial loads.
Thrust bearings are comprised of components which support axial loads, and little to no radial loads. Types include tapered, cylindrical, spherical, and needle roller thrust bearings, thrust ball bearings, fluid-film thrust bearings, and magnetic thrust bearings.