On Saturday, December 3, 2016 at 11:48:55 PM UTC-5, Bob Engelhardt wrote:
On 12/3/2016 10:10 AM, Jim Wilkins wrote:
http://bbs.homeshopmachinist.net/arc...p/t-20828.html
Sulfur isn't a coolant but it bonds to freshly exposed surfaces.

Thanks - the reply there explaining the 2 "regimes" of lubrication was
especially interesting.

That is a really good explanation. I might add one detail: it's not clear to me which types of lubrication are involved, but some lubricants not formulated for cutting (such as motor oil) can cause a cutting edge to skate over the work if the machine isn't sufficiently rigid or if the cut isn't sufficiently aggressive. This is why I cringe when people discuss cooking up their own brews of cutting oil, including the use of ATF. I have no idea how any individual concoctions perform, but the chance you'll get that combination of normal lubrication and extreme-pressure lubrication right seems pretty slim. Unless you use a lot of it and like to experiment, I'm strongly in favor of buying the stuff that's made and tested to do the job right.

--
Ed Huntress