Thread: #30 machine oil ????

I need to change the oil in a lathe head stock. The lathe is a ww2 Sebastian 12x36. I have ordered a manual for it, and have downloaded a manual for a similar machine, and it calls for 30wt machine oil in the apron and headstock.
Does that mean something similar to Mobil Velocite # 10 (30) spindle oil, or I am off track on that.
I am used to oiling up an old "O" model South Bend 11", not a gear head.

Way off with Velocite 10. That's ISO 10, or about SAE 5.

What they are looking for is a non-detergent SAE 30. You could get fancy and use one of the DTE series, but I'd just use ISO 68 AW hydraulic oil.

Never use automotive oil in a machine. Automotive oil contains dispersants and heavy metal additives that promote contaminants to remain in suspension for removal by the oil filter. Machine oil in contrast, promotes coagulation allowing contaminants to settle to the bottom of the sump. The viscosity index of oil can be expressed by several systems like SAE and Saybolt indexes as well as others. Most of these are based on drain time through an oriface. There are probably conversion charts somewhere on the web, but I am not aware of them. I can say that 30 wt(SAE) is equivalent to 250 to 350 (Saybolt). This weight oil is typically used in gearboxes, aprons and low speed plain bearing headstocks. High speed oil designed for roller bearing headstocks is typically 5-10 wt (SAE) or 100-150 (Saybolt).

You need to be very carefull in comparing old oils to new. Most of the old, straight weight oils were not temperature compensated. That's one of the reasons for 2 different Saybolt scales.

Having said that, 30 weight oil is actually more viscus than ISO-68, but because of the lack of temperature stabilizers, ISO-68 is probably the best choice.

It's getting anymore where the anti-wear additives don't have an additional cost or can actually be cheaper. A gallon of Mobil DTE 26 is $20 at ENCO.
JR

For a start, I do not use automotive oil in machine tools. I was looking for information that would point me in the right direction. As I said the old lathe likes Mobil Velocite #10 for it's Bronze bearings.
The new lathe is a gear head, with Ball & Roller bearings. From the direction that you have pointed me in I am, looking at Mobil DTE 68 (20wt), or 100 (30wt) as possible candidates for the head stock oil.

My old Curtis air compressor calls for 30 non-detergent oil. I had trouble finding it in auto stores. But good old Harbor Freight Tools have it, labeled air compressor oil.

Larry