Boston Gear NBG3521/2 Replacement Set Screw Locking Bearing, 2.500' Bore: Mounted Bearings:. Boston Gear NBG3521/2 Replacement Set Screw Locking Bearing, 2.500" Bore: Mounted Bearings:. This NBG3521/2 replacement bearing is for use with 's set screw locking series of mounted bearings for medium duty applications. It has an extended inner race for greater torsional stability. It has 2 set screws for secure attachment to the shaft, and it has a 2.5" bore. This replacement bearing is suitable for use with the MB, MBF, and MBP series of set screw locking mounted bearings.。Mounted bearings combine a bearing mounted inside a housing unit. The bearing housing replaces the need for a casting or weldment to position the bearing securely for reliable operation, and its design determines the type of insert bearing. Insert bearings use rolling elements (ball, cylindrical, spherical, barrel, needle, spindled, or tapered) to maintain the separation between moving parts to reduce rotational friction, and to support radial and axial loads. Available in a variety of materials and mounting configurations, mounted bearings can be one- or two-piece, they can have an extended inner ring and locking device, and they can have seals and end caps that retain lubrication and protect the working parts of the bearing from environmental debris. Mounted bearings support shafts in a variety of mounting configurations (flange block, hanger, pillow block, and take-up block), and are used in a range of applications from light duty shaft guidance on conveyors to road building equipment and crushers.。 manufactures gears, gear drives, bearings, valves, shaft collars, couplings, and other power and fluid transmission components. The company, founded in 1877, is headquartered in Charlotte, NC, and meets International Organization for Standardization (ISO) standard 9001:2008 standard.。 。 。 。