Today there are many excellent lubricants for the full spectrum of spindle applications. The OEM should always be the first source for lubrication requirements. However, if that information is not available HST makes the following recommendations.
Most spindles that operate under 12,000 RPM are greased for life and require no additional lubrication after assembly. But we have seen grease spindles operating over 60,000 RPM.
There are three primary components to precision grease lubrication for bearings:
- lubricant selection
- application method
- the volume of lubricant to be delivered
The quantity of lubricant or “fill” is a function of the rated spindle speed. In grease lubricated spindles it is critical that the precise amount of lubricant is applied; not too much, not too little. Bearing manufacturers provide fill data based on the operational parameters of the bearing. Our precision metering system lets us apply exactly the prescribed amount. Extreme caution should be exercised to maintain the highest qualities of cleanliness. HST precision lubricates all grease spindles in a separate “mini clean room”. And we use only ultra-filtered grease specifically formulated for high speed spindles.
Several manufacturers have recently introduced new formulations specifically blended for very high speed spindle applications. Kluber NBU15 is our default grease for spindles with dN of less than 150,000. Kluberspeed072-22 is HST’s default lubricant for all high speed grease lubricated spindles with dN in excess of 150,000. Barden – Arcanol L75 is the same excellent lubricant privately labeled.
Both of these lubricants work well with steel and ceramic hybrid bearings. Although most grease applications are for speeds below 600,000 dN, these new greases are formulated for ultra-high speeds up to 1,500,000 dN.
All grease spindles must be “run-in” to avoid subsequent lubricant related failures. This is a process where the spindle is operated at incrementally increasing speeds. Spindle temperature is carefully monitored during run-in. The spindle cannot be accelerated to the next speed increment until the temperature “breaks”. Incorrect run-in can cause the grease to be pushed away from the bearing track and result in a premature failure.
Proper Run-In is required to:
- Expel excess grease from the bearing running track
- Orient the lubricating film on the contact surfaces
- Establish low equilibrium operating temperature
Run-in can take in excess of 12 hours depending on the speed and nature of the spindle. This is a procedure that cannot be rushed.
HST uses Mobil DTE oil lubricants. However, as with grease there are a number of fine oil lubricants on the market. The following ISO standard viscosities are recommended by bearing manufacturers:
- Oil Injection: ISO VG10 or ISO VG 15
- Oil Mist: ISO VG32
- Air-Oil: ISO VG68