From Newsgroup: rec.crafts.metalworking

When it comes to cutting have you ever seen anybody demonstrate clearly
in front of you in an observable manner that one cutting oil is better
than another?

I've been a big fan of Tap Magic for a long time, and I honestly don't remember how long its been since I changed the 1/4-20 tap in my cordless
drill or the 10-32 tap in the tapping head in my mid size drill press.
Only a drop or two in a hole often makes the difference between slipping
the clutch and tapping cleanly in one go without adjusting the clutch.
(DON'T ADJUST THE CLUTCH.)

That being said I've been just using whatever is handy lately. Tapping milling, drilling, turning, parting, and saw cutting... whatever. Tap
Magic, Rapid Tap, Ridgid Dark Thread Cutting oil, or WD-40. When I was a
kid all I often had was 3 in 1 oil so that's what I used for drilling.

I think I am leaning towards Ridgid Dark Thread Cutting Oil for
everything (well everything that doesn't get flood coolant). Its cheap
and it seems to just work. Its less than $30 a gallon retail.
Industrial suppliers charge more, but if they do that there is always
the local hardware store or even a box store, and they often deliver
same day. Sometimes for free.

I didn't plan to use the Dark Thread Cutting Oil. I had about a half
gallon I had grabbed with some other stuff last time I was in my dad's
old shop and it was just sitting there. I first used it on the lathe
turning and parting some 4140QT. My only complaint is the smoke, but if
I crack the back overhead door a few inches, and one of the front
overhead doors I get cross ventilation pretty much all the time. I was
just using it because it was there.

There is an unopened gallon jug of Tap Magic on the floor next to my
desk I ordered a while back, but before it arrived I just started using
the Ridgid Dark Thread Cutting oil, and haven't gotten around to filling
my Tap Magic oil bottles back up yet.

Back in my teens I used a lot of that Ridgid cutting oil standing out
back of our hardware store in the sun power threading pipe with a pipe
drive. Soak it with a few squirts of oil and thread it in one press of
the foot peddle. I bet I was using about 100 times more oil than was
really needed. LOL. Never broke a die, and never wiped the threads on
a pipe though.


*** Another kind of snake oil ***

In lead castings there is an old saw about using candle smoke as a mold release. Its been going around like it was the magic sauce for well
over 40 years that I know of. The thing is lead doesn't stick to
aluminum molds. Maybe the stingy coat of soot acts as a minuscule
insulator to slow the freeze by a fraction of a second. Maybe it acts
as a lubricant on castings that don't have any draft angle, but I never
felt it was worth the trouble. Then people started touting Frankford
Arsenal Dropout. Its a graphite spray that works about the same as
candle smoke as near as I can tell. Maybe marginally better, but that
may just because its easier to get a tiny bit thicker more uniform
coating. People also claims both work for molds that are difficult to
fill. Maybe, but I think any help there is more along the lines of the
mold is hotter on the second or third pour when they finally get around
to spraying in their mold release. I can tell you that I don't see any difference between Frankford Arsenal Drop Out, and generic hardware
store graphite spray lube in performance. I have both.

You want to know the real magic sauce for lead casting molds that are difficult to pour? Baby powder. The old stuff with real ultra fine
talcum powder. The new stuff with corn starch I am told works, but I
have not tried it. I still have a stock of the "good" stuff that got
Johnson and Johnson sued over inflated asbestos claims. A lot of molds
that just wouldn't pour will pour and even flash when lightly dusted
with fine talcum powder and the loose powder blown away or dumped out.
It might act as an insulator maybe, but what I think really happens is
there is no carrier to stick the particles to the mold. I think the
fine particles break up the surface tension of the lead and allow it to
flow out better like rain on a dirty car.
--
Bob La Londe
CNC Molds N Stuff

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