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