Lathe & Mill lubricant (for the machine)

[Dgrose]

I searched the forum and read a lot of information about coolant and lubes for the lathe and milling machines. It appears water based coolants are for heavy production and probably not suited for the weekend warrior (the water rusts stuff and causes bacteria growth). If the goal is not to "cool" the tool but rather assist in the cutting action, then a heavy oil like Ridgid Dark Threading oil can be used. My question is: Can the lathe and milling machine sumps be filled with this heavy oil? I filled my lathe with a couple of gallons of the Threading oil and I use it when I have to use the parting tool (that thing is driving me nuts!). The lubrication pouring from the spout when I turn on the pump helps keep that parting tool from getting stuck and breaking. What is the downside of pouring a couple of gallons into the sump? Is it bad practice? Will excess bacteria grow? What am I missing here?

I know there are misting systems but I just bought the lathe (PM 1660 TL) and milling machine (Southbend 9x48) and they came with sumps and pumps. Usually I am so timid trying not to break stuff that I probably am not pushing the tool beyond 20% of what it is capable of doing. I see Tom and Abom and Joe P. take huge cuts with carbide not even aware that I could do that. Anyway, right now I am not worried about cooling the tool, just keeping it lubricated.

What do you think. Was putting 2-3 gallons of dark threading oil in the sump a bad idea? Some people have horror stories about their machines rusty but most of those are with water based coolant. I don't think the oil will cause rusting issues.

 

[benmychree]

Yes, bad idea, before long, your machines would be sticky and black, as would be your person and clothing and your shop would stink like sulfur; if you did use a cutting oil it should be a clear light bodied cutting oil with no sulfur added.

 

[Dgrose]

Thanks for the advice. So it would be ok to fill the sump with an oil that is lighter containing no sulfur. Is the sulfur corrosive to metal?

 

[benmychree]

Oil that contains sulfur will stain some metals, especially brass, but is not corrosive. Oils that are intended for use on automatic screw machines would probably be a good choice as they are intended to lubricate as well as promoting free cutting. The one that I use in my power hacksaw is Mobilmet 766, it was reccomended to be cut 50% with kerosene, which makes it cut much cooler.

 

[Dabbler]

Any light oil such as detergent free 30 wt oil will work as a cutting oil/coolant. As long as your chip tray is without holes you'll do fine. You can buy it in 5 and 20 gallon drums fairly cheap.