I feel I should add a few lines on the subject of coolant/lubricants for machining based on my own work on the chemistry of these.
Not all maching fluids are alike. There are a multitude of formulations out there. Of course some are only available as 200 litre drums and so rarely accessible to the small user.
Firstly neat oils, these have the much longer history and are well understood for their designed purposes. They are the only type to perform well on grinding machines. Surface grinders are very sensitive to the type used.
Secondly so-called suds,these are not actually soluble oils, but often an oil-in-water emulsion, sometimes water-in-oil. Many more formulations exist especially over the last 10 years or so as chemists look at ways of overcoming the deterioration of mixed fluid in the tank. Other problems associated with these fluids are, as mentioned in earlier posts, staining of metal surfaces and most drastic of all, health problems which develop as the fluid ages.
Those health problems can be severe, in one large Midlands plant, now closed, a high proportion of the workforce developed lung problems which lead to the intervention of HSE and was attributed to poor fluid maintenance. There is guidance available **LINK**. and also **LINK** which points to specifics.
There are recently available fluids supplied as concentrates for mixing with water which have shown experimentally and in small and mid-scale practice to be less prone to deterioration.
As this is a topic in which I have a special interest may I ask contributors to be more specific when referring to the fluids they use and the problems which they experience.
Thank you
JerryNotts