David
As Hopper says for our levels of use pretty much any half logical choice of oil will do the deed. But I used to earn my living as a scientist / R&D Engineer so talking to tech reps first was almost instinct.
Of course that was way before every other person had a chainsaw and pretty much anything could be quickly got by mail order. Back then about all you could easily find local would be the basic petrol filling station and car spares stock stuff or 3in1 from the DIY and bicycle shops.
Always remember a mates reaction when the local motorcycle dealer started selling front fork oil in three grades
"They make fork oil! How much!! You gotta be 'kin joking! Whats wrong with ATF."
Of course down my way ATF in small bottles was a special order item then. Fork oil was, and still is, just ISO hydraulic oil in small bottles with a very big mark up.
Not so sure about ATF in a lathe. Its not really an "oil" more a mix of lots of oily stuff. Theoretically Dextron 3 and 4 is around SAE 10 but that is specified at 100°C. ATF is formulated to have a very stable viscosity from around 60°C to 110°C but it can be about 10 times thicker at 0°C and maybe 4 or 5 times thicker at 20°C. Typical graph on this page **LINK** , click on it to get a readable size version.
Hydraulic oils have a much steeper viscosity change with temperature curve but they are specified to operate at 40°C, see the graph at the bottom of this page **LINK**, and being much simpler mixes are well behaved at different temperatures. Hydraulic oils are anti-foam and have anti wear additives too.
But ultimately the specifics don't really matter. Oily is good, dry is bad, dry'n swarf worse and grinding dust a hanging offence.
Clive
Edited By Clive Foster on 12/05/2020 09:34:02