Way and spindle oil

I am missing something here. Everybody keeps mentioning trapped dirt and water in detergent oil. We are not talking about using used dirty oil out of your car. We are talking about using brand new, never been used before oil on a lathe. Where does the dirt and water come from that you are talking about? I have read this same refrain all over the web but nobody mentions where the dirt and water comes from. I am concerned because if this is such a major issue I would like to know where the dirt and water is coming from so that I can take steps to prevent it getting to my lathe in the first place. I am not trying to be stubborn here. Just trying to figure this out.
 
Most of the comments are out of context, oils are designed for specific applications. The manufacturer tells you what oil to use, typically they will specify an oil viscosity, there are various ways of interpreting the viscosity as to SAE motor oil, SAE gear oil, ISO viscosity etc. So as an example most gear head lathes specify ISO32, or SAE 10 motor oil. This is just the viscosity index at a specified temperature. Most smaller lathes use splash lubrication and do not have filters, so the lubrication is from splash up to the top of the lathe and then channels down to the bearings. Use too high a viscosity, this causes friction which increases the heat of the oil, it also doesn't flow as well to the bearings. Too thin an oil does not provide the film thickness to the bearings and gears. A detergent oil is designed to keep particles in suspension so they can be removed by a filter, no filter, then no detergent. The particles typically settle at the bottom of the case. These can be metallic, or dirt pulled in through the breather. This is often seen as sludge on the bottom, water is also pulled in and condenses in the cases, this will eventually cause cloudy oil and rust.

On ways, and certain gearboxes, ones use way oil which has tachifiers, which help the oil stick and provides a film between the moving parts. Use too thin an oil then you get increase wear. This results in long term wear, Use 3 in 1 oil and you basically have metal against metal because the oil has no film thickness. The oiler systems are what as known as one shot, you oil it periodically, this flushes any chips/dirt and then it falls into the pan. People keep on insisting on using oils that aren't recommended by the manufacturer, short term, any oil is better than no oil. Long term use the wrong oil and you will get increase wear over time. It is rare that one will experience a catastrophic failure, but I have read of headstocks getting very hot when people have used the wrong viscosity/motor oil in a geared headstock.

People buy gallons, because often the lathe headstock will take 1/2-1 gallon of oil when you change it, on the ways, you usually give 2 pumps when you start, and repeat at set intervals while you are working. It is very easy to go through a gallon or more a year if you use your machines. Gear head mills will usually use SAE80/90W gear oil which has the same viscosity as 30W motor oil or ISO 90. You do not use limited slip differential oil, as it is designed for clutch packs. Bottom line, use the specified oil, other oils may work but not as well.

Oil Viscosity.jpg
 
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I am missing something here. Everybody keeps mentioning trapped dirt and water in detergent oil. We are not talking about using used dirty oil out of your car. We are talking about using brand new, never been used before oil on a lathe. Where does the dirt and water come from that you are talking about? I have read this same refrain all over the web but nobody mentions where the dirt and water comes from. I am concerned because if this is such a major issue I would like to know where the dirt and water is coming from so that I can take steps to prevent it getting to my lathe in the first place. I am not trying to be stubborn here. Just trying to figure this out.
The dirt and moisture come from the machine itself and from the environment. As the bearings and gears wear, microscopic debris is created. There is moisture in the air as humidity. Using the correct lube helps minimise the resulting damage. Proper maintenance and cleaning are probably more important to minimizing wear than using any specific lubricant.
 
Thank you Mksj for your detailed explanation. Looked in the owners manuals for my craftsman 12x36 lathe and QCGB. Calls for SAE 20 machine oil for lubrication and makes no reference to way oil. Cross referenced SAE 20 machine oil and found that the SAE 20 range includes AW 46 and AW 68 hydraulic oil as the modern equivalent. I can find AW 46 all over the place for under $15 per gallon and in one gallon jugs. The smallest size for AW 68 is 2 gallon jugs and larger with prices starting in the mid $30 range. My lathe gets light home use. Less than 10 hours per week and some weeks it doesn't get used at all. I am going to try the AW 46.

Thanks to everyone for your comments.
 
Without a filter for circulating oil. do not use detergent oil in gear boxes. With simple closed bath oil systems, let the metal and dirt settle to the bottom of the reservoir, rather than circulate through the gears and bearings. Oil filter, detergent oil. No filter, non detergent oil.
 
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My Craftsman 12x36 lathe is belt driven. No gear box. Just a lot of points to lubricate whenever I use the lathe. I picked up a gallon of AW 46 today at my local auto parts store. $16. I probably have a lifetime supply. Thanks again to everyone for their comments.
 
One other thing, I put a large strong magnet in the bottom of my lathe gearbox. Hopefully will catch most of the bits of suspended iron in the oil.
I epoxied a magnet into the drainplug. When I change the oil, I can wipe the crud off the drainplug before I put it back.
 
I am missing something here. Everybody keeps mentioning trapped dirt and water in detergent oil. We are not talking about using used dirty oil out of your car. We are talking about using brand new, never been used before oil on a lathe. Where does the dirt and water come from that you are talking about? I have read this same refrain all over the web but nobody mentions where the dirt and water comes from. I am concerned because if this is such a major issue I would like to know where the dirt and water is coming from so that I can take steps to prevent it getting to my lathe in the first place. I am not trying to be stubborn here. Just trying to figure this out.


Much of the USA has a fairly humid climate, so when temperatures drop moisture will condense on many surfaces, particularly metals, such as your machine ways condensation will also occur inside gear heads and other enclosed spaces. Unlike car engines, lathes and other machines should not get hot enough to boil this moisture out, so it just accumulates until you drain it out.

The dirt, well it depends on what sort of dirt you have, but consider a typical workshop, machining cast iron produces much fine dust. the use of angler, grinders, bench and surface grinders, linishing belts, not to mention tool post grinders. All of these will produce a lot of abrasive dust, dirt call it what you will, and it is the enemy of machines. frequent and generous oiling helps to flush it away

We have a fairly dry climate where i live, however occasionally we get a few humid days so I still give my lathe a good squirt down with Inox MX3, a product similar to WD40, RP7, CRC Etc. Although far superior to all of them. I also use it as a cutting oil, it's highly recommended for difficult metals like stainless, Aluminium, titanium etc, but also very good on steel. and stops your tools, machines and machined parts from rusting.

I also use chain bar oil on the open gears outside the headstock. just a very light drizzle while lathe is running slow is all it needs every few months. It resists flinging off and dripping, it helps the gears to run quiet and smooth.
 
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