Maximum Capacity SRDG Ball Bearings
(See also: TMB SRDG Ball Bearings)

These bearings are designed to the same envelope dimensions as the original SRDG bearings described above but carry a 20% to 35% higher dynamic load rating. (The load at which a bearing will achieve an L10 life of one million revolutions), it also carries a substantially higher static load rating. (The static load rating is identified as the maximum load that can be applied to the bearing without resulting in permanent deformation of the bearing components.) These increased load ratings are the result of adding more balls to the "normal" SRDG ball bearing; therefore the load is carried by more balls at any one time.

Because the Conrad construction method does not allow more balls to be added to the bearing, the rings are slightly modified by cutting a small notch, or filling slot, on one side of the raceway (in both inner and outer rings). The bearings are constructed using standard Conrad procedures, up to and including the inner ring being snapped into position. The rings are then rotated until the filling slots are in line with each other and additional ball(s) are inserted into the bearing through the filling slot. The balls are evenly distributed around the raceways and the retainer installed.

The increased load carrying capabilities of the maximum capacity, or maximum type SRDG ball bearing, are intended to support primarily radial loads. Thrust loads, from either direction, will cause the balls to ride up onto the sides of the raceways and into the edge of the filling slots. This will very quickly cause permanent damage and premature bearing failure.

NTN’s designation for the SRDG maximum capacity bearing is a BL prefix in front of a three (3) digit base bearing number.

Examples of the NTN Maximum Capacity, SRDG Ball Bearing Series

Note: This design is becoming less popular due to improvements in Conrad type bearings, such as NTN’s TMB bearings, which permit the replacement of max. type bearings with no performance penalty.

A recent development in bearing technology has yielded a greatly improved version of the standard SRDG conrad ball bearing, the TMB ball bearing. This specially heat-treated bearing transforms a standard 6200 or 6300 series SRDG ball bearing into a bearing that offers substantially longer life than standard or maximum capacity SRDG bearings. TMB bearings offer the following advantages:

• TMB bearings run quieter than the standard maximum capacity SRDG ball bearing;
• They are capable of taking thrust loads where maximum capacity SRDG ball bearings cannot because they do not require a filling slot;
• TMB bearings have a rated L-10 life over 2 times the standard 6200 and 6300 series SRDG ball bearings; and,
• They offer greatly increased bearing life in heavily contaminated applications.

NTN’s designation for this type of bearing is the prefix TMB, before the three (3) digit base bearing number.

Examples of the NTN TMB Bearing Series