"Bob Engelhardt" wrote in message
...
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.

It will. You can run HSS up to around 1000 deg. F -- a dull red glow.
Carbide can run much hotter. Most of us never see those temperatures on old
or small lathes. If you have a real industrial lathe, less than 40 years
old, you might want to think about cooling. Otherwise, lubrication is likely
to be more important, and cutting oil lubricates much better than coolant
does.


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?

It can reduce cutting forces and, yes, it reduces chip friction off of the
tool. It often improves finishes. It increases the life of cutting edges. By
reducing cutting forces, it can help stabilize the work temperature -- which
is the only worthwhile reason to run coolant on a small or old lathe.
Coolant does that job better.


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

Thanks,
Bob

Now you've opened a real can of worms. g

FWIW -- and only as an aside, because we don't usually use these tools in
HSM work -- really advanced multi-coated tools, diamond-coated tools, and
ceramic tools should NOT be run with coolant on a milling machine. Those
tools can't stand the repeated thermal shock. They're usually run dry, or
with a very lean mist.

--
Ed Huntress