Friday, May 26, 2017

Design and Characteristics of Ball and Roller Bearings

DOUBLE ROW SELF-ALIGNING BALL BEARINGS utilize an inner ring with two rows of balls, in two deep raceways; and an outer ring with a single spherical raceway.  In this way, the inner and outer rings can be misaligned relative to each other.  The resulting affect is a comparatively large angle imposing moment loads upon the balls.

The boundary dimensions of the 1200 and 1300 series are the same as the 6200 and 6300 single row deep groove bearings.

CYLNDRICAL ROLLER BEARINGS have rollers which are essentially cylindrical in shape.  This provides a modified line contact with the cylindrical inner and outer ring raceways, while the rollers are guided by ground ribs on either the inner or outer ring.  The cylindrical shape allows the inner ring to have axial movement relative to the outer ring (except the NH type).  This is especially important when accommodating thermal expansion when both rings must be press fitted.



In this series, the NJ, NF, and NH types can carry light or intermittent thrust loads.  The bearings utilizing machined bronze cages are suitable for high speed operation.

The NN3000 and NN3000K series are available in high precision tolerances and are well suited for use in machine tool spindles.

TAPERED ROLLER BEARINGS utilize conical rollers and raceways arranged so that the rollers and raceways meet at a common apex.    The rollers are guided by contact between the large end of the roller and a rib on the inner ring.  This provides high capacity for radial and single thrust loads.

SPHERICAL ROLLER BEARINGS have two rows of rollers in separate raceways which allows the bearing to compensate for angular errors.  They have large radial and thrust load capacity for heavy shock and impact loads, suitable for heavy industrial equipment.

DUPLEX BEARINGS use a set of two on a common shaft with the inner and outer rings clamped solidly together.  They are used to gain axial shaft control, rigity and extra capacity.

There are three fundamental combinations n duplex bearings: face to face (DF); back to back (DB); and tandem (DT).

The back to back mounting (DB) has the load lines through the balls converging toward the outside of the bearing.  This arrangement is preferred when the pair of bearings is to resist moment loading.



The face to face mounting (DF) has the load lines through the balls converging  towards the axis of the bearing.  This arrangement is less sensitive to slight angular errors in mounting of the bearings.

The tandem mounting (DT) is arranged so that the load lines through the balls are parallel to each other.  This mounting is used when it is desired to divide a heavy thrust load between the two bearings.  Since this mounting carries thrust load in one direction only, a third bearing should be provided to take thrust load in the reverse direction.

SINGLE DIRECTION THRUST BALL BEARINGS consist of two washers having ball grooves ground into their adjacent faces with balls and cages mounted between these grooves.  They are normally equipped with either pressed or machined cages and are suitable for carrying thrust loads at moderate speeds.

DOUBLE DIRECTION ANGULAR CONTACT THRUST BALL BEARINGS are back to back duplex bearings with a larger contact angle than that of normal angular contact ball bearings.

These bearings have been recently developed, and are primarily designed as thrust bearings for machine tools.  They utilize machined brass cages.

SPHERICAL ROLLER THRUST BEARINGS are similar to double row spherical roller bearings, but have a greater contact angle.  They are guided by ground flanges on the inner ring and operate against the spherical raceway in the outer ring.  The contact angle is approximately 45⁰.  Machined cages are normally used and oil lubrication is recommended.

Thursday, April 27, 2017

Explorer class bearings promise faster speeds & improved reliability

Explorer high-performance, long-life bearings range now includes an improved single-row angular contact ball bearing that delivers a number of benefits for designers and operators of screw compressors, pumps, and gearboxes seeking to reduce the total cost of ownership of this equipment through improved reliability and energy efficiency.

Featuring a redesigned brass cage that delivers reduced noise and vibration levels and improved robustness, the new 40° contact angle bearings significantly increase the limiting speed up to 30 % compared to the previous design.



The new cage geometry and the use of stronger brass material reduce cage contact forces and increase cage strength, ensuring greater tolerance of shock loads and vibration, while delivering the significantly higher speed capability even under severe operating conditions.

In addition to the redesigned 40° contact angle, a new contact angle of 25° is also offered, giving the bearing a further 20% increase in speed over that of the 40° version, while enabling higher radial loads to be accommodated. In each case, the ball-to-cage contact arrangement allows cooler running and greater temperature stability, while noise and vibration levels are reduced by 15% in both the 40° and 25° versions.



Sealed variants of these bearings are also available for applications that may be more difficult to maintain, preventing contaminants from entering the bearing during installation and subsequent operation. Bearing arrangements that include a 40° contact angle unit taking the main load with a 25° unit acting as a back-up bearing offer improved robustness for applications where the axial load is predominantly in one direction, resulting in longer service life.

Explorer class bearings are the result of years of development and accrued expertise in bearing design, tribology, metallurgy, lubrication and machining techniques. The new 40° and 25° Explorer class single row angular contact ball bearings are an attractive option for operators of screw compressors, pumps and gearboxes seeking cooler running, more energy efficient and longer life bearings that will ultimately set their products apart from the competition.