wrote in message
...
On Sun, 12 Feb 2017 18:15:13 -0500, Ned Simmons
wrote:

On Sun, 12 Feb 2017 14:25:30 -0800, wrote:

To all the greasy folks here,
About 7 years ago I took apart my dividing head to make some
changes.
I completely degreased all the parts. When re-assembling the thing
I
used white lithium grease on all the parts that needed grease.
Lately
the rotating parts have become very stiff, as if the brake was on.
I
took it apart today and discovered that the white grease had turned
into green glue. But only on the steel worm and bronze worm gear.
The
all steel tapered roller bearings at both ends still have grease
that
works and looks like grease is supposed to. It appears that there
is
some kind of chemical reaction happening between the grease and the
bronze gear. Anybody here know anything about this?
Thanks,
Eric

Some sulfur containing EP additives are not compatible with copper
bearing alloys. It's a common concern with gear oils. I've never
heard
of an issue with grease, but if the grease was made from oil with
non-compatible additives...
Greetings Ned,
I tried to find out what kind of oil is used in the white grease I
have and have had no luck. But I'm thinking you must be correct
about
the sulfur, even though the grease is not described as having any EP
additives. Based on your post I am going to make sure that any
greases
I use in the future on bronze mechanisms do not contain sulfur or
any
other additives that can harm bronze. The grease in contact not only
became a substance similar to thick glue parts of it turned into
almost a solid. And conventional solvents used to dissolve greases
had
no effect I could see on the morphed grease when I cleaned it all
out.
Eric

http://www.machinerylubrication.com/...ur-ep-gear-oil
"Sulfurized mineral oil will readily stain copper under the conditions
of the Copper Corrosion Test (ASTM D130), which uses a copper test
strip, submerged in the test oil at 100°C for three hours as an
indication of chemical reactivity to yellow metals."

Also search for the Copper Mirror test.
-jsw