Nardini MS350 Oil Pump Knocking Noise??

Hi

I ran my Nardini MS350 lathe for the first time today.
I hear a knocking sound at higher rpm. I am reasonably confident that the noise is coming from the oil pump. The sound is consistent with a weak or broken return spring in pump allowing the eccentric driven pump plunger to launch and then bang as returns. The oil pump is still pushing a lot of oil up to the sight glass.

I can't imagine that Nardini of the time (probably around 1970s) allowing the oil pump to knock. Am I wrong?
Later versions of the Nardini probably use the same oil pump. Is a broken/weak pump spring a common problem?

Getting the pump out to replace a spring looks difficult. It is buried in the bottom of the head stock under the spindle.

It looks like there is a thick layer of sludge that has hardened in the bottom. Looks like you will need lots of brake clean and rags to get it cleaned out. Start cleaning!

My 2 cents, not knowing much of anything about that lathe. Is there a clutch? I don't see it, and I also don't see the black grunge from worn clutch material.

You mention you see oil flow in the sight glass. That is good but not an assurance of delivery everywhere it is needed. Have you tried running it with the cover off? Another less messy option is to pour oil into the distribution tray. Also, look for flow through each feeder hole. Some feeder holes are metered, making flow non-obvious. Also more prone to clogging.

I would be concerned that the system may not be delivering oil to the bearings, potentially due to gunk in the lines. Also, I wonder about the root cause of the suspected pump failure. There is a reason it failed, and it might be important to know.

I see oil is delivered to the oil distribution tray at the top, and then it runs by gravity into pipes and various places. Looks like spindle bearing oil is fed via the troughs at each end. Avoid any temptation to blow air through those pipes and bearing feed holes (unless you can catch the outflow). You'll just force crud into your bearings. When working on the headstock, take great care not to allow dust and dirt in there. Is there a filter in this oil system?

As Slingtoe mentioned, it looks like there is gooped oil in the reservoir tray. Probably want to plug feed lines while doing any initial cleaning.

Hopefully someone here has done this before and can offer experience. I expect tearing into that headstock might involve replacing some seals, clips, and misc bushings and bearings. Sure would be nice to have those, and a maint manual, before you begin.

It looks like a pretty simple oil system and it may be entirely gravity fed. If it was my lathe, I would strongly consider not tearing it apart if this is the only issue. I would look hard at retrofitting an external oil pump. I figure it would use the drain plug, filter the oil, along with a catch magnet, before delivering it to that distribution tray.

Hi
I posted 2 pictures. The first was after removing the lid the first time. The second is after cleaning out all the sediment and old oil. The pump is directly under the spindle in the centre of the pictures. It is held in with 2 socket head screws. The plunger presses on an eccentric on the shaft located under the oil tray. The plunger is cone shaped. The pump was factory installed before the headstock casting was painted yellow inside.


The pump is still pumping a lot of oil. Far more than the distribution system can handle. The oil is gravity fed from the tray. All the surplus just overflows the tray.

There is a screen on the pump intake and the felt pad in the tray is supposed to trap sediment. I have fitted a magnet into the tray as well. There isn't a proper oil filter. I'd like to fit a proper filter but there isn't much spare space. I could wrap the screen with some sort of filter media, but I haven't researched the options.

There may be nothing wrong with the pump. It only knocks at higher rpm. It is possible that the return spring, as designed, is not strong enough to suck in a full stroke of oil at higher rpm, so the pump plunger doesn't follow the eccentric. One option would be to replace the MS plunger with a lighter plastic version.

To do anything, I would really need to take out the spindle to get access to the pump and attached plumbing.

Dazz