Motor oil in lathe gearbox

I have a large Monarch lathe built in 1944. It has a geared head,a plain bearing spindle and some sort of oiling pump to lubricate it. I
use the machine about once a week for half an hour or so at a time, I live in Canada and my shop is unheated. The belt drive setup was originally setup for a maximum speed of 500 RPM but I changed it so that it goes up to 1000 RPM because I came across a very similar Monarch lathe set up this way from the factory.
I noticed it was low on oil and I was in a rush to fix my tractor so I added 4 litres of 10W30 motor oil that I had on hand to get it to the proper level. Is this ok or have I done something stupid?
stan
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I think the only concern is that a detergent oil will hold water in suspension. In an engine the water gets heated out, the lathe doesn't get hot, so you have to run the lathe up to 10,000 RPM to get it hot enough to keep the oil water-free or, change the oil out more frequently.

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Having been in the middle of restoring an American Tool Works lathe which had EVERY wick and oil passage packed off with hardened gunk (might have been older waxy oil, solidifying in the wicks), I'd urge you to get it out as soon as its convienent to do so and replace it with the right stuff.
Gregm
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replying to Greg Menke, John Medeiros wrote: Aloha Greg! Will need your assistance in determining the year of manufacture of our ATW 14" lathe (ser. # 46871). It has the US Navy stamp & inspector initials too. Thanks! John Koloa Rum Company
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It won't damage it upon contact. :)
But I suggest you drain it out and put in the oil that the manufacturer recommends. It's not clear that the oil you put in has the correct viscosity.
Jim
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Almost any oil is better than no oil, but the correct is best.
stanley baer says...

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Not the worst thing you could do. 10W30 will be a bit thin when cold but this is not the most critical application in the world.
I would not run the machine too fast because with motor oil instead of regular gear oil, you may get foaming, which is messy. 500 or 1000 RPM sounds like no big deal.
Keep in mind that if it really does take gear oil, 90W gear oil is about the same as 30W motor oil in terms of consistency.
Tim.
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You never use detergent oil in a lathe, mill, etc. that does not have circulating oil pump and a filter!
Detergent oil keeps particles in suspension, which means that the particles are always going to be wearing away metal. Non-detergent oil allows particles to settle to the bottom, where that don't do any harm and can be removed by washing out, whenever the oil is changed. Multiweight oil when cold/cool is always the lighter of the viscosity number. In effect you have put 10 weight oil into your machine. Then there is the concern of what are the detergent additives doing. Are they collecting moisture (likely), are they compatible with your bearings (old type solid bearings if used), with your seals? Maybe Ok to use in an emergency by it should be changed.
Jim
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replying to Greg Menke, John Medeiros wrote: Aloha Greg! Will need your assistance in determining the year of manufacture of our ATW 14" lathe (ser. # 46871). It has the US Navy stamp & inspector initials too. Thanks! John Koloa Rum Company
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