I've been using air tool oil to lubricate my steam engine. Is this a good oil to use?
There's not much difference between an air tool and a steam engine besides the gas of choice.
There is a huge difference actually, in that hot steam easily "floats & strips" regular oils away.
True steam oil contains a small percentage of organic fats that have the ability to "stick" to the hot, wet surfaces to maintain a layer of lubricity in spite of the hostile environment.
However, on a different note, low pressure and temperature steam that is "saturated", which is what our toy steam engines operate on, actually does provide a modicum of lubrication, in that there is constantly a fine "skin" of water coating all the surfaces within the cylinder.
In a real steam engine operating at high temperatures and pressures, there is no such water in existence within the cylinders, as the steam is actually "dry" in that situation, besides which the forces involved in such an engine would far outstrip the meager lubrication ability of water, which can only work as a rather poor lubricant when there are no significant forces involved.
If you are running at just an atmosphere or two of pressure, you are likely fine, but as the pressure goes up and the sophistication of the engine increases, true steam oil does become important. Like the difference between a small Mamod and a large Stuart.
Depending on what you are actually running, you are probably fine using air tool oil, or no oil at all, but in the long run it would certainly be better to use a true steam oil, even for our little toy and model engines.
Hope that helps.
Just to add to Stokers advice, a lighter steam oil is best for models. The most common to be found is 460 and while this is fine for most models some of the smaller ones may benefit from the lighter 220.
I think it's best to use steam oil exclusively. I use 460 no matter how low the steam pressure.
Steam oil is cheap enough and easy to find, so you might as well use it.
I personally only use 480 oil for anything that needs lubrication (steam domain speaking).
Will the steam oil from Jensen's website work good?
However, on a different note, low pressure and temperature steam that is "saturated", which is what our toy steam engines operate on, actually does provide a modicum of lubrication, in that there is constantly a fine "skin" of water coating all the surfaces within the cylinder.
In a real steam engine operating at high temperatures and pressures, there is no such water in existence within the cylinders, as the steam is actually "dry" in that situation, besides which the forces involved in such an engine would far outstrip the meager lubrication ability of water, which can only work as a rather poor lubricant when there are no significant forces involved.
If you are running at just an atmosphere or two of pressure, you are likely fine.
Hope that helps.
I've been using air tool oil on the working parts, and not the cylinder.
And for what steam engine I'm using it on, look to my profile photo, very small oscillating engine. (though I have a Schoenner coming soon)
So you are just using it as a journal and bearing oil, and it should work fine in that application, though most any common oil, like 3 in 1 would do the job as well. The port faces and pivot for your oscillator would likely benefit from a drop of steam oil, providing a slightly better seal and reduce wear on those critical surfaces. But there are many a small oscillator that have run their whole lives sans any significant lubricant, and still run to this day.
For my small toy steam engines I have sometimes used the old Green Velvet on the parts that move together while immersed in steam. One small 4oz bottle last me decades.
But mostly I use ZOOM Spout , or 3-In-One electric motor oils , or sewing machine oils for the external moving parts. Keeping any moving part as clean as-can-be sure seems to make a difference with either oil. So I have used compressed air on a needle blow tip to remove micro crud , then I oiled up the parts.
For years I heard rumors of some steam oil being similar to 600 Model T oil with about 5% beef tallow?
I have an old vial of delicate machine oil for instruments from ca. 1907 and I think it smells a bit like whale oil.
I recall many years ago air compressor and early air tool repair shops used to strongly push for synthetic air tool/compressor oils because of the sealing materials, they feared some older oils may be deteriorating the o rings etc etc.
I am also a fan of Zoom-spout for moving parts and the empty containers come in handy to fill with gas for priming full size engines
As a side note, I remember a test being done on what protects metal from rust best and steam oil was right at the top, so if you do use steam oil and it gets on any bare metal, you might be doing it some good