Wednesday, 28 November 2012

SMB Ceramic bearings...

Just a little update on the full ceramic (ceramic rings & balls) & hybrid ceramic (steel rings & ceramic balls) bearings that we currently have in stock.  Please just call us (01993 842555) or email (sales@smbbearings.com) if you'd like to make a purchase or just need some more information/advice...

Full Ceramic:

Full ceramic bearing ZR02 (Zirconia rings & balls/PTFE cage)
Zirconia ZR02 bearings
CC6000 ZRO2 - full ceramic bearing/PTFE cage, dimensions 10x26x8mm
CC608 ZRO2 - full ceramic bearing/PTFE cage, dimensions 8x22x7mm
CC626 ZRO2 - full ceramic bearing/PTFE cage, dimensions 6x19x6mm


Full ceramic bearing Si3N4
(silicon nitride rings & balls/PTFE cage or full complement)
Silicon Nitride Si3N4 bearings
CC608 Si3N4 F/B - full ceramic bearing/full ball complement, dimensions 8x22x7mm
CC6806 Si3N4 F/B - full ceramic bearing/full ball complement, dimensions 30x42x7mm
CC687 Si3N4 F/B - full ceramic bearing/full ball complement, dimensions 7x14x3.5mm
CC689 Si3N4 F/B - full ceramic bearing/full ball complement, dimensions 9x17x4mm
CC6806 Si3N4 F/B - full ceramic bearing/full ball complement, dimensions 30x42x7mm



Hybrid ceramic bearing- steel/stainless steel rings & ceramic balls)
Hybrid ceramic bearings
Our famous skate bearings - CB608TW-2RU P5 - chrome rings & ceramic balls, rubber seals, dimensions 8x16x5mm - buy these direct from our EBAY SKATE SHOP.

SCB6002 - stainless steel rings & ceramic balls, dimensions 15x32x.9mm
SCB626 - stainless steel rings & ceramic balls, dimensions 6x19x6mm
SCB6801 - stainless steel rings & ceramic balls, dimensions 12x21x5mm
SCB6807 - stainless steel rings & ceramic balls, dimensions 35x47x7mm
SCB6810 - stainless steel rings & ceramic balls, dimensions 50x65x7mm
SCB6902 - stainless steel rings & ceramic balls, dimensions 15x28x7mm
SCBR144TWZW09 - stainless steel rings & ceramic balls, one metal shield, dimensions 0.1250x0.2500x0.1094"


We can order other sizes in from the factory for you, so please contact us if you need any further information or advice.


Some notes on CERAMICS...

Zirconia (suffix "ZrO2")

• Good corrosion resistance to cold water and many chemicals
• Good high temperature performance up to 300C without cage
• Non magnetic and electrically insualting
• Lower speed and load than steel bearings
• Not suitable for low noise applications
• Higher fracture toughness than other ceramics so better for small shock loads
• Expansion similar to steel so not a problem to use with steel shaft at high temperature.


Silicon Nitride (suffix "Si3N4")

• Very good corrosion resistance to water, salt water and most chemicals.
• Good high temperature performance up to 1000C without cage
• Non magnetic and electrically insulating
• Lower speed and load than steel bearings but Si3N4 balls are used in high speed hybrid bearings.
• Not suitable for low noise applications
• Much lighter than steel or Zirconia
• Very low expansion at high temperature.

Bearings can be supplied with steel rings and ceramic balls (hybrid) or "all ceramic" bearings with ceramic rings and balls. These all-ceramic bearings may have PTFE or PEEK retainers or be supplied as full complement type.

Hybrid bearings (CB/SCB prefix) have steel rings and ceramic balls. Silicon nitride is the most popular for the balls as it has only 40 percent of the density of bearing steel but is much harder giving greater wear resistance. Zirconia is heavier with 75 percent of the density of steel so is less suitable for hybrid bearings.. Hybrid bearings are also capable of higher speeds. Sometimes, excessive claims are made about the high speed capabilities of hybrid bearings. They can run faster than all steel bearings due to the lower centrifugal force generated by the ceramic balls but this is partially counteracted by the lower elasticity of the balls. As the balls are harder, the contact area between the balls and the raceway is smaller which causes a higher contact pressure which can can cause the raceways to wear faster. The speed increase for hybrid bearings is approximately 30-40 percent with adequate lubrication. Hybrid bearings can also operate better with limited lubrication but running speed should be reduced. Hybrid bearings are also less subject to ball skidding under inital acceleration.


All-ceramic bearings (CC prefix) have good to excellent corrosion resistance, are non-magnetic and, apart from silicon carbide, are electrically insulating. All-ceramic bearings can be used in high to very high temperatures if supplied without a cage (full complement).

  • Electrical resistance: Si3N4 best, then ZrO2, then SIC which is conductive.
  • High temp resistance: SiC best (1600C), then Si3N4 (1000C), then ZrO2 (300C)
  • Corrosion resistance: SIC (excellent), then Si3N4 (very good) and ZrO2 (good)
  • Load capacity: SIC highest then Si3N4, then ZrO2
  • Fracture toughness: ZrO2 best, then Si3N4, then SiC
The limiting speeds for all-ceramic bearings are lower due to the lower precision and roundness of the rings and the loads are lower because the material is more brittle. Under heavy loads and particularly heavy shock loads, there is a risk of cracking. For the same reason, great care should be taken with interference fits. Zirconia is the least brittle so it will handle shock loads and very small interference fits better than the other ceramic materials with silicon carbide being the most brittle but generally, shock loads should be avoided. Using ceramic bearings on steel shafts at high temperature can cause bearing damage due to the large difference in expansion coefficient. For more information see Shaft/Housing Fit


WARNING: Hybrid bearings can offer very low frictional torque but the bearing rings must have very good roundness and a high quality raceway finish while the balls must also have very good roundness and surface finish. A lower quality hybrid bearing can have much higher friction levels and a lower maximum speed than a good quality all-steel bearing... 

Any questions?  Please feel free to contact us for further assistance!





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