It is understood that most bearings are typically replaced after damage occurs. However, for certain bearings where repair costs remain reasonable, we opt to undertake restoration work.

When design reference surfaces become excessively deformed and unusable, alternative surfaces must be selected as references, necessitating the reorganisation of dimensional chains. For instance, if the bearing housing exhibits significant deformation, the rotating assembly should serve as the reference. The housing is then reworked and calibrated, after which the assembly dimensional chain is adjusted according to the reworked housing dimensions. Using fitted adjustment rings, repairs are carried out in sequence according to the dimensional chain arrangement, ultimately achieving the objective of controlling the precision of the closed ring.

When repairing and adjusting dimensional chain accuracy, adhere to the principle of reference coincidence by selecting only one reference surface—the design reference—while basing repairs on all other functional surfaces against this surface. This combined reference approach facilitates accuracy verification and minimises cumulative error. For instance, in repairing speed-regulating hydraulic couplers, the bearing housing is commonly employed as the reference.

1. Suitable viscosity and favourable viscosity-temperature characteristics

To prevent excessive spindle temperatures causing thermal deformation of the machine tool, which could compromise machining accuracy or lead to inadequate lubrication of NSK bearings, lubricants with appropriate temperature ratings must be selected based on spindle bearing structure, rotational speed, and bearing clearance. These lubricants should exhibit favourable viscosity-temperature characteristics to prevent significant viscosity fluctuations during substantial variations in spindle operating temperatures and ambient conditions, thereby maintaining reliable lubrication performance.

2. Excellent lubricating properties

To maintain a uniform oil film between the spindle and bearing contact surfaces, and to prevent film breakdown during impact loads from spindle start/stop movements, superior lubrication is essential. This reduces friction and frictional heat, minimises spindle temperature rise, and safeguards machining accuracy.

3. Excellent oxidation resistance

When employing recirculating lubrication systems, spindle NSK bearings require oil that remains stable over extended periods without degradation. Consequently, superior oxidation resistance is imperative.

4. Effective rust prevention

As lubricants inevitably incorporate condensed moisture from the air or machine coolant during spindle operation, the oil must possess robust rust-inhibiting properties.