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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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