Re: Question on coolant vs lubricant when milling & the need for each

Hi Eric,

you have most of the reasons why people use coolant.
another is that some metals expand or shrink when they get hot and
that either changes the metal properties or makes you wait for the
part to cool and then verify the actual dimensions.

If you think of the coolant as a heat transfer process, then you will
get a better understanding of what you might need to do to get where
you want to be.

Machining in a freezer is out, so the added coolant is a very
attractive option.

Flood cooling is simple, you can just hang a bucket and let it drain
onto your cutting area. Cheap and just as dirty as pumped coolant.

Spray mist is another very simple option, it too will deposit liquid
that has to be drained or collected, although in much smaller
quantities.

cold air, like the vortex generator you mentioned offers the cooling
effect, but does take energy. A very small unit will not require too
big of an air compressor, but if you need a lot of cold, you need a
lot of air. Search the web for a table of one of the suppliers, you
will find that you can get small ones that use less than one CFM at
100 PSI.

The engineering is that water has roughly 10 times the capacity of
air to remove heat. a small Spray mist unit will remove much more
heat than cold air than a medium sized vortex generator.

Lastly lubricant. Lubricant will reduce the forces necessary to
remove metal. for a simple test, dry tap a 1/4 inch thread in a 1/4
inch steel plate. Then repeat with cutting oil. The forces go way
down and that means so does generated heat.

Not to beat up on vortex generators, but they offer no lubrication.
So do not reduce the amount of heat generated.

Like was mentioned, use some WD 40 on a cut and you will see the part
and cutter stay much cooler.

Lastly, water in any form will rust exposed metal. use a good
additive AND oil your machine when not in use.

Hope this helps. and I think this thread is getting a little far off
topic so I think I'm done with it. if you have any questions, e-mail
me off list, but I think I covered it pretty well here. BTW, there
are some sales this month on mister units. IF you get one, make sure
it has adjustments for air pressure, air volume and liquid volume.

Dave






This is pretty common on drill presses

--- In CAD_CAM_EDM_DRO@y..., glee@i... wrote:
>
> I'm trying to get a clear understanding of the need for coolant vs
> lubricant when milling.
>
> In my scenario, I am using a Sherline Mill, cutting aluminum with a
3/16 or
> 1/4" end mill. I tried using a 1/8" cutter but that was a disaster
so I'll
> stay away from that for a while.
>
> Now that you know what I am cutting here's my question:
>
> Am I correct in my understanding that the primary objective of any
cutting
> fluid is to both keep the cutter from overheating and also to move
chips
> away from the cutter? (Perhaps not in that priority)
>
> Now, based on my understanding of the above, correct or incorrect,
is there
> any reason that I cannot use one of those really neat vortex cooler
devices
> with a source of compressed air and keep the workspace clean? This
would
> both cool the cutter and bow the chips away. I assume that if
this is not
> the proper thing to do that there must be good reason....
>
> I know that the sherline is a small mill and that aluminum is a
soft metal
> as metal goes. Am I making a big deal about nothing given the small
size of
> my mill, cutter and block I am able to cut with this size of mill?
>
> I'd welcome some feedback.
>
> Thanks,
>
> Eric Mack