Just for the experience, I tried cutting a 0.625" diameter brass rod off
with a BXA-7 cutoff tool, both dry and wet, even though all the books
say that brass is best cut dry.

Dry, it squealed loudly but cut nicely at ~800 rpm, yielding random
piles of little brass needles as long as the cutoff blade was wide.

Wet with oil emulsion (Rustlick WS-5050), it squealed very quietly at
the same speed, but yielded mirror surfaces. The wet piles of little
brass needles sitting on the top of the cutoff blade were not random,
instead looking like stacked firewood, and the needles ended up in neat
piles rather than going everywhere.

A better lubricant might eliminate the brass squeal entirely. Steel cut
off in the same setup does not squeal at all.

So, cutting brass wet actually helps, at least with an oil emulsion.
This ties in with the historical use of whole milk as a cutting fluid
for brass and copper, milk being an emulsion of butterfat in water.

At least WS-5050 doesn't turn rancid.

Joe Gwinn

Lots of non-recommended methods work, just not quite as well as the
recommended ones. Often for one-off jobs it doesn't matter. The
Cincinatti "Milling & Milling Machines" book from Lindsay describes
cutting speed and coolant tests on cast iron, for example. There
wasn't much difference with or without oil, so they suggested milling
dry to avoid the mess (pp. 123-4). Textbooks present that as a hard
rule with no explanation.

I start with the same cutting oil on everything including aluminum and
brass and only change to the recommended fluid when there's a problem
that sharpening the bit doesn't solve, which isn't often.

Jim Wilkins

In article
,
Jim Wilkins wrote:

Lots of non-recommended methods work, just not quite as well as the
recommended ones. Often for one-off jobs it doesn't matter.

Umm. I'm reporting that cutting wet (a non-recommended method) in fact
works a lot better than cutting dry (the recommended method).


The Cincinatti "Milling & Milling Machines" book from Lindsay describes
cutting speed and coolant tests on cast iron, for example. There
wasn't much difference with or without oil, so they suggested milling
dry to avoid the mess (pp. 123-4). Textbooks present that as a hard
rule with no explanation.

I have not read this book, I think. I'll have to check.

My report is about brass, not cast iron, but I did read somewhere that
some companies cut cast iron wet to keep the iron dust under control.
Apparently the wet mess was less a problem than the dry mess. Or at
least the mess stays in one place, and doesn't get into everything.
With flood cooling and a filter, the problem would certainly be
controlled.


I start with the same cutting oil on everything including aluminum and
brass and only change to the recommended fluid when there's a problem
that sharpening the bit doesn't solve, which isn't often.

I'm certainly going this way. I have yet to run the experiment on cast
iron, but I will. But it may not be soon, as have to get some cast iron
first.


Joe Gwinn

On Jun 5, 5:01*pm, Joseph Gwinn wrote:
In article
,
*Jim Wilkins wrote:

The Cincinatti "Milling & Milling Machines" book from Lindsay describes
cutting speed and coolant tests on cast iron, for example. There
wasn't much difference with or without oil, so they suggested milling
dry to avoid the mess (pp. 123-4). Textbooks present that as a hard
rule with no explanation.

I have not read this book, I think. *I'll have to check.

My report is about brass, not cast iron, but I did read somewhere that
some companies cut cast iron wet to keep the iron dust under control. *
Apparently the wet mess was less a problem than the dry mess. *Or at
least the mess stays in one place, and doesn't get into everything. *
With flood cooling and a filter, the problem would certainly be
controlled.

Joe Gwinn

The 1919 book said that coolant stopped heat distortion of odd-shaped
or fragile parts but the grit damaged machine bearings. I don't cut
fast or deep enough to overheat the tool or work and a little oil (or
tapping fluid) from a brush or needle oiler seems to be enough. Maybe
my old, slow, worn machines mask effects that would be important for
more aggressive cuts on newer ones.

Jim Wilkins

In article
,
Jim Wilkins wrote:

On Jun 5, 5:01*pm, Joseph Gwinn wrote:
In article
,
*Jim Wilkins wrote:

The Cincinatti "Milling & Milling Machines" book from Lindsay describes
cutting speed and coolant tests on cast iron, for example. There
wasn't much difference with or without oil, so they suggested milling
dry to avoid the mess (pp. 123-4). Textbooks present that as a hard
rule with no explanation.

I have not read this book, I think. *I'll have to check.

My report is about brass, not cast iron, but I did read somewhere that
some companies cut cast iron wet to keep the iron dust under control. *
Apparently the wet mess was less a problem than the dry mess. *Or at
least the mess stays in one place, and doesn't get into everything. *
With flood cooling and a filter, the problem would certainly be
controlled.

The 1919 book said that coolant stopped heat distortion of odd-shaped
or fragile parts but the grit damaged machine bearings. I don't cut
fast or deep enough to overheat the tool or work and a little oil (or
tapping fluid) from a brush or needle oiler seems to be enough. Maybe
my old, slow, worn machines mask effects that would be important for
more aggressive cuts on newer ones.

My recollection is that the book that suggested wet cutting of cast iron
said that it didn't improve the machining, but the iron dust in the
factory got into everything, man and machine alike, and was very
annoying, in the same manner as sand in a sandstorm. The sole reason
given to cut wet was to trap the dust.

As for the grit getting into the bearings, that sounds like a machine
design issue either way. The flow of air or fluid should be arranged to
move the grit away from critical areas.

I've been using a Noga mister on the lathe, mainly so I don't get blue
emulsion flung everywhere. The drill press is set up for flood cooling
with the same emulsion. The problem with misters is that breathing the
mist doesn't feel good, so I wear a 3M dust and mist mask.

Joe Gwinn

On Jun 5, 10:00*pm, Joseph Gwinn wrote:

As for the grit getting into the bearings, that sounds like a machine
design issue either way. *The flow of air or fluid should be arranged to
move the grit away from critical areas.

Joe Gwinn

The machine designers didn't have synthetic rubber for seals in 1919.
Some of our old home machines may have the same concerns. My 1965
South Bend lathe is an update of a 1920's model.

I read their long discussions to mean that a little lubricant is
enough to improve surface finish and a flood of any cheap coolant
greatly improves high speed production. For intermediate amounts, "The
average small stream as usually provided, is by no means sufficient to
secure ample cooling."
The book contains many observations and test results but generally
expects the reader to decide how to apply them.

Jim Wilkins