Grey cutting oil

Went to use my CNC Bridgeport today and found that the soluble cutting
fluid had gone grey! No nasty rancid smell, and it hadn't
de-emulsified - it's only been in for a matter of maybe 5 weeks, with
occassional use cutting aluminium alloys.
The soluble oil is 'Excelfluid LC' from J&L, and I use it in all my
machines (manual Bridgeport, 540 Surface Grinder, Cylindrical Grinder
etc) - it occassionally goes rancid, and usually de-emulsifies if left
unused for a bit but I've never had it go grey. This was a dark
'machine grey' Very odd.
Is it possibly some strange reaction with aluminium alloys?
AWEM
Reply to
Andrew Mawson
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Dead rats in the sump?

Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Reply to
Tim Leech
Is this an ordinary soluble oil, or a synthetic/semisynthetic fluid?
I only ask because I have a synthetic type in my Bridgeport, the guy at Rock Oil recommended it for machines which aren't used all the time, less likely to go rancid than the conventional soluble oils. That's gone a funny brown colour, but no nasty smells & it still works fine.
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Reply to
Tim Leech
In Bromley ?????????? Nah they taste like chicken
-- Regards,
John Stevenson Nottingham, England.
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Reply to
John Stevenson
cutting
Grinder
No, as far as I no it's bog standard soluble oil.
AND no rats here - what do you think it is - some old canal side dry dock!
AWEM
Reply to
Andrew Mawson
Since suds is normally kept a bit alkaline and aluminium will dissolve in alkalis (as well as non-oxidising acids), you may well have hit on the answer. Don't know if it will cause any problems though.
Mark Rand RTFM
Reply to
Mark Rand
Mark is probably right. Try a bit of pH paper in the fluid. If the suds are significantly alkaline you could well be dissolving Al out of the alloy, leaving the other components behind
Reply to
Norman Billingham

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