On Wed, 11 Mar 2015 08:46:29 -0700 (PDT), Gerry
wrote:

Is there any important reason not to use the clear version of Rigid threading oil for drilling/threading on my mill and/or lathe? I do not use flood coolant very often so most of the time I'm using a brush to apply to the work

If you're speaking of the thick oil that Rigid sells for threading
pipes, manually or by machine, it's not very good for general
machining. It's meant for use at very low speeds and at the highest
pressures. It's too thick.

You'll do much better with a lighter oil made for machining. I use
mostly plain lard oil, which I've used for over 30 years, but there
are better oils. Look for a "straight" (also called "neat") oil if
you're applying it with a brush. Soluble (water-miscable) oils are not
made for that, although they'll work reasonably well. They're
formulated for cooling and are not very good lubricants. I was given
some by a manufacturer of the stuff (Master Chemical), who told me to
mix it very rich for use on my old South Bend, and it did the job. But
straight oils are better, IMO.

The hard part is finding them in small quantities. DoAll, Acculube,
Castrol, and several other companies make them. Petroleum-based,
lard-based, or vegetable-oil-based probably doesn't make much
difference.

If you're tapping by hand, use one of the cutting products made for
that -- Tap Magic, etc. They also sell cutting oils in small
quantities.

--
Ed Huntress