On Jun 26, 3:14*pm, Joseph Gwinn wrote:
In article ,
*Bob Engelhardt wrote:

Joe's recent thread about his dribble cooling for his lathe reminds me
of questions that I have.

1. *What is the purpose of cooling? *Does the tool get so hot without it
that the edge is dulled? *I thought HSS & especially carbide could stand
the temperatures created by HSM work.

The first purpose of cooling is primarily to prevent welding of chips to
cutting tool, which causes effective dulling. *The second purpose is to
keep the tool itself cool, so the cutting edge won't become soft. *With
modern tool steels and carbides one can go far faster before this
happens, but cooling always allows one to go faster than dry.

2. *What is the purpose of cutting oil? *I remember reading that it
allowed chips to flow off the cutting edge more easily. *Is that it?

Reduces cutting force by lubricating the interface between tool bit and
workpiece. *This usually results in better surface finish, and may yield
better accuracy as well.

3. *Does choice of cooling or lube depend upon the tool (lathe, mill,
drill press, band saw), or material? *Or both? *

It mostly depends on the material being cut. *This is discussed at
length in Machinery Handbook.

Coolants have various combinations of cooling effect and lubrication
effect. *Plain water (used when machining some plastics) is a pure
coolant. *Wax is a pure lubricant. *Oil in flood is a lubricant with
significant cooling ability. *Oil emulsion in water does both. *And so
on. *One can make a career of this.





*I'd like to fill in the chart (my guesses shown):

* * * * * * *Mild *Cast *Tool*
* * * * * * Steel *Iron *Steel *Alum *Brass

Lathe * * * *? * * *D * * ? * * *? * * D

Mill * * * * ? * * *D * * ? * * *? * * D

Drill * * * *? * * *D * * ? * * *K * * D
press

Band * * * * W * * *D * * ? * * *? * * D
saw

C = coolant
L = lube
D = dry
K = kerosene or equiv
W = wax

* - actually I don't care about Tool Steel, as I never use it. *It's
included for completeness

There are tables in the Machinery Handbook.

If you really want to dive into the details, there is a book, a tome to
be precise. *There was a thread on this titled "Metal Cutting
Principles, the tome" posted on 14 April 2007. *

The book is "Metal Cutting Principles", 2nd edition, Milton C. Shaw,
Oxford University Press, 2005, 651 pages. *

I will say that parts of this book are very heavy going.

Joe Gwinn- Hide quoted text -

- Show quoted text -

Joe,

I noticed that Shaw has a doctorate in chemistry. ( http://tinyurl.com/l27kaq
) Does he use chemical explanations for the role of sulfur in helping
metal cutting operations? (sulfur cutting oils/high sulfur steels)
It seems unlikely that a chemical reaction would have time to
influence cutting, but who knows. Some reactions are fast and it
could be that surface chemistry is involved. Maybe lead-based cutting
fluids would be effective (if not for environmental/health problems).

This book has a chapter on coolants and lubrication:
“Metal Cutting” by Edward Trent & Paul Wright: http://tinyurl.com/p2l94p
It says that a more effective place to direct cutting fluid is along
the flank of the cutting tool or from underneath the cut.