Newbie query -- Cutting oil vs. cutting fluid (for lathe work)

[ghp3]

New to metal working and this forum. Bought a second-hand Taiwanese clone of an Emco Compact 8 lathe in support of projects for high power rocketry. I've been primarily working with graphite up until now, but will be starting a project to make aluminum parts. I'm aware of the need to using a cutting lubricant to keep heat down and allow for smoother finishing, but am encountering both "cutting fluid" and "cutting oil" without getting a sense of what the functional difference is between the two and which one would work best for my application.

Thanks!

ghp3
Pittsburgh, PA

 

[GaryK]

New to metal working and this forum. Bought a second-hand Taiwanese clone of an Emco Compact 8 lathe in support of projects for high power rocketry. I've been primarily working with graphite up until now, but will be starting a project to make aluminum parts. I'm aware of the need to using a cutting lubricant to keep heat down and allow for smoother finishing, but am encountering both "cutting fluid" and "cutting oil" without getting a sense of what the functional difference is between the two and which one would work best for my application.

I believe that cutting fluid is used in a flood coolant or mist system, whereas oil is usually applied manually via a brush or squirt bottle.

Gary

 

[Rbeckett]

I am pretty sure Gary hit the nail squarly on thiis one. I generally make my own with ATF, Mineralspirits and kerosene. Gotta waych extreme high heat but work nicely as a cutting oil and general penetrant. It also helps keeep my lathe and mill oiled and protected from rust due to the high humidity in F;a. Mc Master and several vendors have a water soluable system for pretty reasonable money if you want to go that way too. I prefer the Petro based fluids since I am very hit or miss on machining activities and don't want rust to creep it's ugly head in while I am indisposed or unavailable to go to the shop for a while.
Bob

 

[HSS]

For turning aluminum, or ally for our friends across the pond, WD40 works just fine.

Patrick

 

[DMS]

Coolant and cutting fluids are less about cooling and more about lubrication and clearing chips. The main thing with aluminum is that you need something to fend of chip welding. Aluminum is very soft; Under pressure the chips like to mash together and weld to each other, your cutter, and the part itself. The glob of metal left on the cutter is referred to as a "built up edge", and trust me, it will get you cursing. WD-40, as stated before, works great on aluminum for preventing built up edge. A water soluble cutting fluid like CoolMist 77 in a squirt bottle also works just fine. If you use a water based lube, I would recommend mopping up after a session, as it can stain if left on the bed ways, or trapped between the gib and cross slide, etc. A small bottle of CoolMist will last a long time (you put about a tablespoon in 32oz of water as I recall), and WD-40 only requires an occasional spritz, don't need to douse things.