Last update April 30th. 2016

Watchmaker's Cone Bearing Lathe Lubrication 

February 27th. 2016

G. Boley recommendation is based on close clearances of the cone bearings of the lathe spindle. The tighter the clearances are, the higher the friction between the surfaces of the bearings. 

The lower the viscosity of oil, the lower the friction is, thus the requirement for oil with low viscosity, but with as high lubricity* as is possible.

*Lubricity 1 is the main property of a lubricant, most adequately defined as the resistance to rupture of the boundary film. 

Mobil Velocite, No.4 Spindle oil, recommended by G. Boley, according to the ISO 3448 is VG 5 viscosity class.

Here are the specs of Mobil Velocite Oil group 


The ISO classification of viscosity is recommended for industrial applications. The reference temperature of 40°C represents the operating temperature in machinery. 

For example. ISO VG 22 refers to a viscosity grade of 22 cSt ± 10% at 40°C. 

The viscosity at different temperatures can be calculated using the viscosity at 40°C and the viscosity index (VI), which represents the temperature dependency of the lubricant.

Not being able to procure the Mobil Velocite Spindle Oil Nr.4, I have used the ISO 3448 classification to find suitable replacement.

My search for replacement resulted with a choice of Castrol Hyspin E5 Spindle Oil which fulfilled requirements for use with close clearances cone bearings. 

To the right, the specs of the Castrol Hyspin Spindle Oil group

Here are shown two spindle oils from different makers.

Unfortunately the only source for Mobil Velocite No.4, that I could find, the cost for the quantity of 50ml exceeded the cost of 500ml of the Castrol Hyspin E5 high speed spindle oil.

Lubrication is accomplished only through capillary action.

Second image shows cap of oil reservoir removed.

Recommendation for the cone bearings lubrication, provided by Schaublin3 regarding the oil reservoirs of the type shown above.

Of course the usual checkups should be applied:

- Never leave belt tightened on the pulley, 

- Before running the lathe spin the spindle by hand to spread oil over the cone bearings, 

- Always check that there is enough oil in oil reservoirs.



1 -   "Tribology of Miniature Systems" - Zygmunt Rymuza - Elsevier 1989 - page 334
2 -  

"Fluid Film Lubrication - Osborne Reynolds Centenary" Leeds-Lyon Symposium on Tribology Proceedings - University of Leeds. Institute of Tribology.; Institut national des sciences appliquées de Lyon.; et al - Elsevier 1987

3 -  

Schaublin SV 65 Lathe - Service Manual - page 5



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