Ever had one of those days when nothing works!

[chola]

Thought I would post this here as a bit of a heads up for fellow machine tool users.

I went back out to the shed a few weeks ago to get some lathe work done (after a good month or so away from the lathe due to illness).

As my lathe is CNC controlled, I secured the bar stock in the chuck, loaded up the g-code program, and stepped back to 'watch the magic'!

Almost instantly things were grating, groaning and just not doing what they should!

After much thought (and almost as much swearing), I decided to check everything on the machine.

Turns out that during this period of non use, the grease that is applied to the lead screws, and the cross slide mating surfaces had pretty much gummed up, and while not impossible to move, obviously put some extra strain on the stepper motors that controlled each axis (hence the grinding and groaning - those of you that have ever heard a stepper motor 'stall' due to too much load against it will know what I am talking about).

After pulling the lathe apart, washing all parts down in kerosene, and applying a generous coating of high temp lithium grease to all moving surfaces it runs like a champion! I even went so far as to lap and polish the mating surfaces of the cross slide and the jib strips. As a result I can apply greater pressure to the jib screws thereby increasing accuracy, minimising chatter, and lessen wear on the moving parts.

I also pulled the 3 jaw chuck apart and gave it the same kerosene bath and re-packed with generous helpings of lithium grease...now when tightening or loosening the chuck it literally purrs like a kitten.

Why this happened...who knows, could have been a combination of a period of not being used, and the fact we had about 2 weeks of pretty solid rain during this time that played havoc with the grease, or the grease just 'wore out' in its ability to lubricate (it happens to engine oil, I assume grease to be no different)....

Bottom line here is, don't forget about regular machine maintenance, not just a quick brush down after use, all those chips and dust end up somewhere...and alloy dust in grease and oil makes a great grinding paste...not really what you want attaching to the leadscrews, especially if machining softer materials that will generate a lot more dust (wood, resin, some plastics).

I hope this helps out anyone who is wondering why their machine is 'not just working right'.

Take care, and machine on brothers!

[MPWR]

Haven't heard of this happening before- any idea what kind of grease was on there originally? I'd always assumed that engine oil breaks down because of heat, but grease (except for attracting dirt) usually doesn't need to be changed. Sounds like it was lucky you didn't burn out a stepper motor.

Does the lithium grease seem to be working well for you? I'm still using sewing machine oil on my leadscrews, but I figure some good lithium or molybdenum grease would be a good upgrade.

[chola]

G'day MPWR,

When I originally unpacked the machine , cleaned and greased it, I used a plain Castrol grease on the leadscrews and mating surfaces. Can't rememebr what the grease's actual application was for, don't believe it had any lithium content, long since thrown the container out, but it had been on the machine for a while.

On closer inspection the grease had gone 'milky' in colour, making me think moisture had gotten to it.

I guess grease doesn't need to be changed under 'normal' conditions, such as in wheels bearings etc, but then again, normally the grease is pretty well sealed fromt the elements as well, not exposed as on the lathe. Perhaps a mechanic can give us an idea here of if/how grease breaks down, or if it does...where's Mike Mechanic?

Yes, lucky the stepper didn't burn out, but I was pretty quick with the off switch.

The new Grease is a high temp Lithium type from Penrite and is working great, and it's not that expensive. For memory it was for marine applications, but any good quality lithium type should work fine. I did use the lithium spray on grease in an aerosol can previoulsy on other components, but don't believe it offered any thing other than convenience (that, and I liked the smell of it!!!), but for the price, I wouldn't bother buying spray on lithium grease again.

How do you find the machine oil works? I considered that in the early days, but figured a generous coating of grease would be able to suspend / hold off the particles of metal from the leadscrew, making it less likely that they will be 'ground' into it, but more 'pushed along' it. I only use oil now on the bed-ways, hypoid gear oil, nice and thick, give the ways a good even coat before starting a run, and after when cleaned up, to protect the surfaces.

I guess the most important thing before applying grease / oil, is a good clean surface to start with. Get out the kerosene, a few containers, a wad of newspaper, new paintbrush (don't use an old one already encrusted with chips), and spend a few hours pulling the machine apart, cleaning everything, then lube it up.

I think from here on in I will give the machine a 'tear down' every 6 months maximum, for a good clean and adjustment.

Be good if anyone on the forums buys a new machine to maybe post a step by step on cleaning and adjustment. I know there are other sties with this information, but still be a good resource to have available here I reckon.

[MPWR]

I have to admit that the biggest reason I use light machine oil is that it works as a good do-all on my bench. It goes on my leadscrews and slides, but it also works nicely for cutting fluid. My shop is fairly humid , so the light oil also helps keep surface rust down.

It does the trick for keeping things slippy, and it doesn't seem to collect dirt and debris very quickly. I've certainly never had it gum up, and it's easy to clean. The only real disadvantage is reapplying it regularly, but it doesn't need to be reapplied more than every month or so.

[chola]

G'day,

I know what you mean with a 'one size fits all' oil.

I guess it depends how often you use the machine as to the frequency of oiling / greasing etc.

My machine gets basically 9 hours of continual use twice a week, churning out parts by the quantity, but you need to establish a suitable cleaning / maintenance routine for your own cirsumtances for long life and reliability.

[mikemechanic]

Originally Posted by chola

I guess grease doesn't need to be changed under 'normal' conditions, such as in wheels bearings etc, but then again, normally the grease is pretty well sealed fromt the elements as well, not exposed as on the lathe. Perhaps a mechanic can give us an idea here of if/how grease breaks down, or if it does...where's Mike Mechanic?

Here I am. Grease on a lathe and grease in a car is two completely different things. We do repack wheel bearings (or at least did as they use sealed bearing now) as the grease runs at some extremely high temperatures, friction and brake temps are huge in some vehicles so the grease has a tendency to break down over time. I am almost certain that our lathes will never reach these kinds of temperatures so it really shouldn't break down too much. I assume that if it did break down it had absorbed humidity from the air as it would have been somewhat exposed. I've tried several oils for my lathe but haven't really found one that I am happy with. I will be moving to a high humidity region in the near future so my learning curve will be moving once again.

Mike