688-2RS Ball bearings

Deep groove ball bearings

Demension: 8X*6X4mm, 

1)Materials for rings and rolling elements

While the contact surfaces between the bearing rings and rollingelements are subjected to repeated heavy stress,they must still maintainhigh rotational precission,therefore, the materials used for bearingsrings and rolling elements require the following characteristics:

●High rolling contact fatigue strength
●High hardness
●High wear resistance
●High dimensional stability
●High mechanical strength

The material used by our companyis high carbonchromium bearings steelGCr**-GB/T****4 equivalent such as AISI****0(USA),DIN**0Cr6(Germany)JISSUJ2(Japan) and BS**4A*9(UK).

2)Materials for cages

The materials for cages must have strength to with stand rotation atload and shock load. Low frictional efficiency light weight and be ableto with stand operation temperature.

The material used in ribbon cages or crown cages is *8F or SPCC pressed.

It is chemical compositionis shown for extra-high speed application. Plastic cages such as glass reinforced polymideareused.

These plastic crown have the advantages oflow torque,long grease lefe and low noise,etc.

3)Vibration and noise

● The measuring parameter of vibration adopted by RNB is the vibration acceleration of vibration velocity.

● The measuring units and measuring method are specified by JB/T***4 andJB/T***3 In the process of measuring vibration strictly controllednoise by using acoustics.

4)Internal clearance

Single row deep groove ball bearings are manufacturedwith Normal radial internal clearanceas standard. Most of the bearingsare also available with C3 radial internal clearance. Some of thebearings can also be supplied with as maller C2 clearance or the muchgreater C4 or C5 clearances. In addition, deep groove ball bearings areavailable with reduced or displaced internal clearance ranges. Thesespecial clearances may use reduced ranges of standard clearance classesor partitions of adjacent classes, see designation suffix CN insection.

5)Tolerances

Single row deep groove ball bearings are manufactured as standard to normal tolerances.

Single row deep groove ball bearings are produced tohigher precision than the ISO Normal tolerances. The dimensionalaccuracy corresponds to P6 tolerances, expect the width tolerance,whichis considerably tighter and reduced to

*0/–*0μm for bearings with outside diameter up to **0 mm
*0/–**0 μm for larger bearings.

The running accuracy depend on the bearing size and corresponds to

-   P5 tolerances for bearings up to a *2mm outside diameter
-   P6 tolerances for bearings above *2 mm up to **0 mm outside diameter
-   Normal tolerances for larger bearings.

For bearing arrangements where accuracy is a key operational factor, some SKF single row deep groove ballbearings are also available with accuracy completely to P6 or P5tolerance classs pecifications.The availability of these bearings shouldalways be checked before ordering.

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