Really really interesting!

I would, however, point out one logical inconsistency in the explanation
below.
In forming a "chemical bond" between the tool and workpiece, which "thereby
keeps the tool from direct contact w/ the metal", I would say that you don't
get much better "direct contact" THAN a chemical bond!!

I think what they *meant* to say is that the sulfur somehow loosely bonds
the OIL to the metal(s), thereby keeping the two metals (bit/work mat'l)
from *bonding to each other* under the high temps due to cutting, and thus
preventing dulling.
And might explain why sulfur oil is more effective on steels, because the S
is bonding to both the tool *and* the material.

Uh, *covalent* bonds, in fact... (old, very inneresting amc
thread...)
Similar to the way sulfur vulcanizes rubber, also requiring high temps.

Sulfur is perhaps the most important element in the body's structural
proteins (hair, muscle, skin, etc.), ito of forming their 3D structures
(quaternary structure, in the parlance), via cross-linking--but mostly via
sulfur-sulfur "bridges".
For example, curly hair has more di-sulfide bridges than straight hair.
Perms break these S-S bonds, thus straightening hair, but which will
spontaneously reform, over time.
What makes a fried egg "fried" is extensive S-S bond formations. Not
reversible over time.
Note sulfur in vulcanizing (cross-linking) rubber, as well.

Chlorine (or more accurately, chloride) is thought to be the culprit in
embrittled SS, which is why SS is just so-so in marine applications.

So these effects of sulfur/chlorine are not exact analogies, but
interesting, none-the-less.
--
Mr. P.V.'d
formerly Droll Troll
"BottleBob" wrote in message
...
"Proctologically Violated©®" wrote:


Is sulfur part of what makes "cutting oil" cutting, as opposed to
lubricating? Anything other diffs?

PV:

Here's an explanation on what function Sulfur and Chlorine serve in
cutting oils, from a cutting oil manufacturer.

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http://www.sunnysidecorp.com/metal_working_oils.htm

Sulfur.

This additive performs an anti-wear function in cutting oils by forming
a chemical bond between the cutting tool and work piece, thereby keeping
the tool from coming in direct contact with the metal being cut. There
are two types of sulfur additives, active and inactive. The inactive
compound is used for cutting mild (low-carbon) steels and will not stain
these softer materials. The active sulfur forms a stronger bond than
the inactive but will stain soft metals. So, oil containing active
sulfur is recommended for cutting and broaching the harder varieties of
steel only. The object of this chemical bond is to promote longer
tool life and to keep the tool from welding itself to the work piece
under the severe temperatures created in many metal cutting operations.


Chlorine.

This additive works in the same fashion as the sulfur additive and
tends to complement the sulfur by strengthening the chemical bond (film)
around the tool. For this reason you will often find this additive
used cutting oils that contain a sulfur compound. Chlorine tends to be
liberated to the atmosphere at elevated temperature; therefore chlorine
additives are not particularly useful for extremely high temperature
applications.
================================================== =======

--
BottleBob
http://home.earthlink.net/~bottlbob