Is cheaper hydraulic oil OK?

Well lubed parts do last a long time. If the lube is not preventing metal surfaces from touching then you get wear.
If a gearbox is producing any kind of metal particles I would be more concerned about preventing them than by collecting them.
 
Tozguy said:
Well lubed parts do last a long time. If the lube is not preventing metal surfaces from touching then you get wear.
If a gearbox is producing any kind of metal particles I would be more concerned about preventing them than by collecting them.
Click to expand...

It would be wonderful if that were possible but all known mechanical systems have wear factors. These are often calculated by design engineers and are used to specify maintenance schedules, also to predict service life of parts. The only way I know of keeping any gearbox from producing metal particles is by not running it. Gears meshing and transmitting power will always wear to some extent, hence the discussion of proper lubricants for minimizing wear.

In reading your comment it looks like the expectation is that the lubrication film layer will prevent any metal to metal contact. While that is ideal it's really not practical to prevent any contact, thus there will always be wear. I'm definitely not a lubrication engineer, just a guy who's worked on many mechanical systems and hasn't ever seen one that operates without some wear factor. However, here's an article from the interwebs that addresses this very issue.

www.machinerylubrication.com

The Importance of Lubricant Film Strength

Discover why film strength is one of the most critical lubricant properties for protecting a machine’s internal components.
www.machinerylubrication.com www.machinerylubrication.com

Cheers,

John
 
John,
Thanks for the article, it is one of the better ones I have seen for general info.
The article explains that the objective of lubricants is to prevent metal to metal contact and how it is done. It seems to reinforce what I wrote above (?).
I personally have seen gearboxes last an amazingly long time and believe that a properly designed gearbox properly cared for will show insignificant wear. Parts may fatigue and fail but not from a lack of lubrication. This is not to say that machines can last forever, just for a very long time.

I don't disagree that some machines wear more quickly than others. I don't disagree that your gearbox is producing metal particles. It happens as the paragraph on Wear clearly states

Wear Generation
In conditions where there is inadequate lubricant film thickness between the metal surfaces,

However my lathe gearboxes do not produce metal particles of any significance and I do believe that it is practical to have adequate lubrication in a hobby lathe.
 
Stick a magnet down in yours for grins & giggles.
In a well made piece with quality control present the fit and finish should be such that you'll see very little debris.

If you take a look in my gearhead you'll see a bunch of decent looking well made gears, then there's a couple of oddballs that don't look so finely made.
Guess where the bits come from.
I had a bunch of 'fines' when I changed mine out. I'd wager money the oil had never been changed.
Fines will mess with your bearings just as bad as particles.
 
When my budget lathe was new I openned up the gearboxes and cleaned them out with a vacuum. There were some scary looking 'particles' in the bottoms. The gears looked all good. I cleaned all three gearboxes, put in fresh oil and ran it for a month. Then reinspected and found everything clean. Did it again after a year. Everything was clean again.
I am confident that I will wear out before the lathe will.
 
A good reason to change your oil regularly in particular the stock oil. This is a picture of my gear head mill at it's first oil change and I doubt that it had more than 100 hours of run time. I subsequently changed the oil to a synthetic and there was a noticeable drop in head temperature (which was previously almost too hot to touch after any prolonged use) and I picked up about 150 RPM of maximum RPM. There are differences between oils even with the same ISO ratings, but a lot comes down to the mechanical design, parts quality, operating points and QC. In some applications like compressors the service life of a synthetic oil can be much longer, but you still to deal with oil contamination so one still needs to consider an interval for changes beyond just running hours. Synthetics would make more sense if you operated a machine constantly, but proably not so for intermittent use. Machines typically come with fluids/oils, but worth checking as some may leak out in transport.

IMAG0165.jpg
 
Mark, a picture is worth a 1000 words! Thanks.
Was the magnetic plug original equipment or your doing?
Did subsequent magnetic plug readings show as much grunge on the magnet?

Dan, are you still finding 'fines' when changing the oil or were they only present on the first oil change?
 
Tozguy said:
Mark, a picture is worth a 1000 words! Thanks.
Was the magnetic plug original equipment or your doing?
Did subsequent magnetic plug readings show as much grunge on the magnet?

Dan, are you still finding 'fines' when changing the oil or were they only present on the first oil change?
Click to expand...
hehe, well this is going to be embarrassing to admit, but I haven't changed it since 2014 when I finally got it into my shop.
There's a 'klunk' in 'Low' that I still haven't figured out or repaired.
When I drained it back then I had magnets in the plastic tub and had a bunch of fines like Mark has in his picts.
I've got two or three magnets salvaged from hard drives laying in there currently.
I haven't changed it because, well a.) it doesn't get used all that much, b.) It's got a small leak on the spindle, and c.) I need to tear it down and figure out where the 'klunk' is coming from.
And all that _after_ I scrap and repair the cross slide. So it's on the To-Do list.
If you take a look at the second picture you can see the odd contacting and 'rub-off' of Dykem on the gears in 'Low'.
That's where the 'fines' come from, IMO. While the oil prevents major wear nothing is going to help when it's poorly manufactured or assembled and the clearances aren't as they should be.
Add to that, it's all a splash' system and the upper selector arm relies on splash to lube it.

P1050161__R.jpg
P1050182__R.jpg
 
Tozguy said:
John,
Thanks for the article, it is one of the better ones I have seen for general info.
The article explains that the objective of lubricants is to prevent metal to metal contact and how it is done. It seems to reinforce what I wrote above (?).
I personally have seen gearboxes last an amazingly long time and believe that a properly designed gearbox properly cared for will show insignificant wear. Parts may fatigue and fail but not from a lack of lubrication. This is not to say that machines can last forever, just for a very long time.

I don't disagree that some machines wear more quickly than others. I don't disagree that your gearbox is producing metal particles. It happens as the paragraph on Wear clearly states

Wear Generation
In conditions where there is inadequate lubricant film thickness between the metal surfaces,

However my lathe gearboxes do not produce metal particles of any significance and I do believe that it is practical to have adequate lubrication in a hobby lathe.
Click to expand...

My lathe has external gears, it was built at least 50 years before I was born and will probably still be going 50 years after I'm dead.

Adequate lubrication doesn't mean there will be no wear, and as has already been pointed out in this thread most hobby lathes will probably outlast their owners if cared for properly.

The original question here was what oil will work and I think that has been answered.

If you don't feel the need to put a magnet on your drain plug or sump then don't do it. I suspect if you did and ran your machine for any length of time you would see some metal particles. This wouldn't mean you aren't caring for the machine properly, just that all mechanical systems wear. The rate of wear may be insignificant for your purposes but unless your manufacturer has somehow figured out a way to cheat the laws of physics there will be wear.

That's pretty much all I have to say about it.


Cheers,

John
 
My mill had a magnet in the drain plug, you could see the oil was dark in the sight window when I changed it, and there was a lot more metal particles that weren't caught by the magnet. I do like to capture the oil and look at it with a light and see any sediment and if it is clear or cloudy. Once I put in the synthetic oil in my mill, the oil stayed much clearer visually looking at it through the sight window, the other major difference beyond what I mentioned was much less foaming indicated by less bubbles in the oil. I sold it before I changed the oil again, it was a Chinese BF-30 mill and the quality was less than I would have expected for that manufacturer. I did own a PM-1340GT, changed the oils about once a year, just some very light particles in the oil with the first change which was most likely casting iron dust. I drilled the drain plug center and put in a neodymium magnet (like 8x20 mm), had minimal build up with the second oil change. I will be doing an oil change on my ERL-1340 in a few months and will also a magnetic in it's drain plug.

I feel what is probably significant is that a decent oil have a good additive package such as anti-rust inhibitors and anti-foaming agents, as I indicted in my gear head mill there were a number of measurable difference in performance with a better oil. If you review most US oil spec. sheets for machine applications these additive packages are pretty standard, which brings us pretty much full circle to the initial question that most name brand oils are pretty close in their performance characteristics.
 
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