Hybrid deep groove ball bearings

Deep groove ball bearings are the most widely used bearing type, especially in electric motors. These non-separable bearings are suitable for high speeds. The deep uninterrupted raceway grooves have a close osculation with the balls, enabling the bearings to accommodate radial loads and axial loads in both directions.
SKF hybrid deep groove ball bearings are available with a bore diameter ranging from 5 to 180 mm. They are manufactured to SKF Explorer performance class quality.
Bearings with a bore diameter d ≤ 45 mm are most suitable for electric motors in the power range of 0,15 up to 15 kW as well as power tools and high-speed drives. SKF hybrid deep groove ball bearings in this size range are the most cost-effective solution against electrical erosion.

Basic design bearings

Basic design bearings are available with a bore diameter d > 45 mm (fig. 1). If a small quantity of smaller open design bearings is required, SKF recommends ordering sealed hybrid bearings and removing the seals.

Cages

Depending on their size, SKF hybrid deep groove ball bearings are fitted with one of the following cages:
  • a stamped steel cage, riveted, ball centred (no designation suffix)
  • glass fibre reinforced PA66 cage, snap-type, ball centred (designation suffix TN9)
  • a glass fibre reinforced PEEK cage, snap-type, ball centred (designation suffix TNH)
  • a machined brass cage, riveted, ball centred (designation suffix M)
For additional information, refer to Cages.
The lubricants generally used for rolling bearings do not have a detrimental effect on cage properties. However, some synthetic oils and greases with a synthetic oil base and lubricants containing EP additives, when used at high temperatures, can have a detrimental effect on polyamide cages. For additional information about the suitability of cages, refer to Cages and Cage materials.

Sealing solutions

Sealed hybrid deep groove ball bearings use the same seals as described under Single row deep groove ball bearings. They are lubricated for the life of the bearing and should not be washed or relubricated. The bearings are considered virtually maintenance-free. If they are to be hot mounted, SKF recommends using an induction heater whenever possible. SKF does not recommend heating a sealed bearing above 80 °C (175 °F).

WARNING

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 Seal materials.

Greases for sealed bearings

Sealed hybrid deep groove ball bearings are filled with a high-quality grease under clean conditions. The standard grease, suitable for the most common operating conditions of electric motors and generators, is indicated by the designation suffix WT. Grease specifications are listed in table 1, under grease “WT”.

For additional information about greases, refer to Lubrication.

Grease life

For SKF hybrid deep groove ball bearings, the estimated grease life can be assumed to be at least twice as long as for same-sized bearings with steel balls (→ Grease life for capped bearings). Conditions such as the presence of water or other fluids or vibration can reduce the grease life.

XL hybrid bearings

XL hybrid deep groove ball bearings (designation suffix VA970) are designed to meet the application requirements for electric generators in larger wind turbines. SKF supplies XL hybrid deep groove ball bearings for the most commonly used generator sizes (→ product table).

Hybrid bearings with special steel rings and coatings

Hybrid bearings can be customized for specific application requirements. For additional information about the following variants, contact the SKF application engineering service.
  • bearing rings stabilized for temperatures ≤ 300 °C (570 °F)
  • bearing rings made of through-hardened stainless steel for enhanced corrosion and wear-resistance and with good high temperature properties
  • bearing rings made of through-hardened stainless steel for cryogenic temperatures
  • bearing rings made of high-temperature tool steel
  • coating with zinc chromate or thin dense chromium for corrosion protection
  • coating based on molybdenum for low friction, especially in vacuum or gas applications
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