Thank you, Ed. I've trimmed off the earlier discussion so that the excellent
summary is easier to see, since I expect that others will also be interested
in saving it.

IMO, it's not likely that someone could provide a clearer explanation,
although I suspect that there are still some HSMs that will disagree, mainly
just out of their inability/stubborness to accept clear reasoning.

The only possible exceptions that I can think of would be beginners that
can't properly select, grind or adjust their cutting tools, speeds and
feeds, and therefore assume that poor tool performance must be because they
don't have a coolant system.

The others that earn their living making chips deserve to do whatever they
think is best for them.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Ed Huntress" wrote in message
...

John, we're getting two different subject mixed up here -- flooding the
work with cutting fluid versus the question of soluble oil versus straight
oil. Let me try to summarize my points:

Straight cutting oil is a good lubricant for cutting. Soluble oil is, at
best, mediocre. Coolant is good for cooling; straight oil is mediocre.
Coolant is cheaper, until you get into the real exotic synthetics, which
have little to offer the hobby machinist, anyway.

The lubricating qualities of your cutting fluid are very important when
you're machining in a non-commercial setting and your machine is
low-powered and/or flexible, and if you're using HSS or you're trying to
extend the life of your carbides. Lubricating the cut means much less when
you're using modern, powerful machines and advanced cutting tools with
radiused edges. It may even hinder your cutting if, for example, you're
using a multi-coated tool that contains a thick layer of aluminum oxide or
a top coat of moly disulfide. They both need a lot of friction to do their
job.

Cooling is important if you're doing this for money and you want to
optimize your production rate versus costs. Cooling is all but irrelevant
if you're doing this for fun and you aren't punching a clock, as long as
you're not pushing your tools to the limit of surface speeds they can
tolerate. Few of us hobbyists are pushing our tools that hard, because we
value tool life more than flat-out production rates.

If you have the luxury of flood cooling, and you're willing to put up with
the mess on a machine that isn't fully enclosed, then flood cooling can
help some things. But it's because it's a flood, not because you're using
coolant. And some of the reasons flood systems are used commercially,
particularly in semi-tended or untended operation where you have to clear
all chips automatically and where you can't apply lubricant accurately,
don't apply in the hobby shop. Likewise, unless we're using CNC, we can't
fully enclose our machines to keep the crap inside. A spray shield is
half-assed at best. I've had to stand in the slop that gets around a
shield for hours and days on end. It sucks.

Unless you're a well-off hobbyist with modern machines and you like to
push the production envelope, flood coolant is problematic. And the key
thing for most of us is that we'll do better with straight oil for most
cutting of steel than we will with coolant applied from a bottle, a drip,
or a brush.

I think the key misunderstanding many beginning hobbyists have is the
reasons *why* coolant is used in commercial machining. It isn't for
reasons that apply to most hobby machining. For most of us, oil is better.
And there is no reason, for most of us, to go to the trouble to apply
flood coolant just to cool the cutting tool. The simpler answer is to slow
down a bit so you don't need to cool.

There. g

--
Ed Huntress