Cylindrical Roller Bearings

The prefix describes where the guiding flanges are located, which determines axial displacement behaviour. NU has two flanges on the inner ring and none on the outer: the outer ring can move freely in both axial directions, making NU the standard floating bearing type for accommodating thermal shaft expansion. NJ has one flange on the outer ring and two on the inner: the shaft can move axially in one direction only. NUP has two flanges on both inner and outer rings, locating the shaft axially in both directions — it is used as a fixed bearing position. N has two flanges on the outer ring and none on the inner: the inner ring (and shaft) can move freely in both axial directions. NF has one flange on the outer ring and none on the inner, providing one-directional axial location from the outer ring side.

E denotes the enhanced internal design (also called E-design or optimised design). Compared to the standard design at the same bore and OD, the E-design bearing has a larger roller complement (more rollers and/or longer rollers), an optimised cage design that allows larger rollers, and improved contact geometry between rollers and raceways. The result is a significantly higher dynamic load rating (C) and static load rating (C0) within the same dimensional envelope as the standard design. E-design bearings are directly interchangeable with standard design bearings of the same designation in terms of fit dimensions; the internal geometry improvement is invisible from the outside.

Standard cylindrical roller bearings (NU, N type) are designed for radial loads only and cannot carry axial loads — the rollers and raceways have no axial guidance geometry. NJ and NUP types can carry limited axial loads in one direction (NJ) or both directions (NUP) through roller contact with the guide flanges, but the axial load capacity is typically less than 10–15% of the radial load capacity. For applications requiring significant combined radial and axial load capacity, tapered roller bearings or angular contact ball bearings are the correct choice.

M denotes a brass (machined) cage. Standard cylindrical roller bearings often use pressed steel or polyamide cages. A brass cage provides better performance at high speeds and high temperatures than pressed steel, and better resistance to lubricant degradation and centrifugal loading than polyamide. The EM suffix therefore combines the E-design enhanced roller complement with a brass cage, making the N2200EM and N2300EM double row bearings suitable for demanding service conditions including high speeds, elevated temperatures, and heavy continuous loads.

A double row cylindrical roller bearing (N2200EM, N2300EM) provides approximately twice the radial load capacity of a single row bearing at the same bore, in a single housing that occupies a shorter axial shaft span than two separate single row bearings. Choose double row when radial loads are too high for a single row bearing but the axial space between bearing positions is constrained and the shaft span cannot be increased. Choose two separate single row bearings when more flexibility in bearing spacing is available, when differential thermal expansion between inner and outer rings must be accommodated by a floating arrangement, or when different cage types are required at the two positions.

The 200E and 300E series share the same bore diameter at the same designator (e.g., NU2208E and NU2308E both have 40 mm bore) but the 300E has a larger OD and wider width, providing a heavier cross-section with more and/or larger rollers. The 300E dynamic load rating (C) is significantly higher than the 200E at the same bore. Select 200E when the housing envelope limits the OD or when the 200E load rating is adequate for the L10 life target. Select 300E when radial loads are higher and the larger OD can be accommodated in the housing design.