Designs and variants
SKF standard assortment
- bearings with open ends (fig. 1)
- bearings with a closed end (fig. 2)
- full complement bearings with open ends (fig. 3)
SKF drawn cup needle roller bearings:
- are supplied without an inner ring
- are generally designed with one needle roller and cage assembly – except wide sizes, which incorporate two needle roller and cage assemblies immediately adjacent to each other, with a lubrication hole in the outer ring (fig. 4).
Drawn cup needle roller bearings with open ends (series designation HK, fig. 1)
are available open (without seals) or sealed on one or both sides (→ Sealing solutions)
- are available open (without seals) or sealed on one or both sides (→ Sealing solutions)
Drawn cup needle roller bearings with a closed end (series designation BK, fig. 2)
- are available open or sealed (→ Sealing solutions)
- are suitable for bearing arrangements where they are situated at the end of a shaft
- accommodate small axial guidance forces, because of the profiled design of their closed end
Full complement bearings with open ends (series designation HN, fig. 3)
- are suitable for very heavy radial loads at moderate speeds
are available with open ends and without seals only
Full complement drawn cup needle roller bearings are supplied with a special grease to secure the rollers during transport. However, SKF recommends relubricating after mounting. Depending on the required grade, SKF recommends SKF LGEP 2 or SKF LGWM 1 grease for relubrication. The technical specifications of the initial grease fill and the relubrication greases are listed in table 1.
Generally, drawn cup needle roller bearings run directly on a shaft. However, in applications where the shaft cannot be hardened and ground, bearings should be combined with an inner ring (fig. 5).
Drawn cup needle roller bearings with wide inner rings (fig. 6) provide an excellent counterface for the lips of external G or SD design seals (→ Radial shaft seals with a low cross sectional height).
For additional information about inner rings, refer to Needle roller bearing inner rings.
Certain sizes of drawn cup needle roller bearings can be combined with a needle roller thrust bearing with a centring flange, AXW series (fig. 7), to accommodate combined radial and axial loads.
For additional information, refer to Needle roller thrust bearings.
For applications where a sufficiently effective seal is not available, or cannot be used for space reasons, SKF supplies certain drawn cup needle roller bearings as sealed bearings. The assortment includes:
drawn cup needle roller bearings with open ends (available for 8 ≤ Fw ≤ 50 mm)
- sealed on one side (designation suffix RS, fig. 8)
- sealed on both sides (designation suffix .2RS, fig. 9)
sealed drawn cup needle roller bearings with a closed end (available for 10 ≤ Fw ≤ 25 mm)
(designation suffix RS, fig. 10)
These integral contact seals are made of PUR, FKM or NBR. Sealed drawn cup needle roller bearings are, under normal conditions and with appropriate counterface, an extremely cost-effective solution to exclude solid contaminants and moisture, and retain the lubricant in the bearing.
When capped bearings must operate under certain conditions, such as very high speeds or high temperatures, some grease may leak. For bearing arrangements where this would be detrimental, appropriate actions could be taken.
Associated external seals
- can be used for needle roller bearing arrangements (fig. 6)
- can be supplied for certain sized bearings (→ product table)
For information about associated power transmission seals, refer to Seals.
Seals made of FKM (fluoro rubber) exposed to an open flame or temperatures above 300 °C (570 °F) are a health and environmental hazard! They remain dangerous even after they have cooled.
Read and follow the safety precautions under this WARNING.
The relatively large quantity of grease in the bearings means they can be operated for long periods before relubrication is required (→ Perform calculations). SKF recommends SKF LGWA 2 grease (table 2), if relubrication is required.
SKF supplies needle roller bearings with different features to facilitate efficient lubrication and relubrication.
All double row drawn cup needle roller bearings have one lubrication hole in the outer ring (fig. 4), as standard.
On request, SKF can supply any single row drawn cup needle roller bearing for inside diameters under the rollers Fw ≥ 7 mm with a lubrication hole in the outer ring (fig. 11).
SKF drawn cup needle roller bearings are fitted with one of the cages shown in table 3.
Double row drawn cup needle roller bearings are fitted with two cage assemblies (fig. 4).
When used at high temperatures, some lubricants can have a detrimental effect on polyamide cages. For additional information about the suitability of cages, refer to Cages.