Zerk fittings falling out

[mscheer772]

I've lost 2 zerk fittings on my tractor(one on the loader one for the brake pedal? What could cause this? I also bought a new discthat lost 3 fittings, why?

 

[SPYDERLK]

I've lost 2 zerk fittings on my tractor(one on the loader one for the brake pedal? What could cause this? I also bought a new discthat lost 3 fittings, why?

I dont know for sure in your case, But I have a theory that is an actual fact for my experiences.
1) Fittings exist that have either metric or US thread. Likewise straight thread like a bolt or taper like pipe.
2) Some of the metric and US threads are close and there are cases where one will fit loosely and tighten in the others hole. In this case the fitting can easily lose its seat pressure and spin right outwith vibration. Any straight thread has this problem, but a poor/loose thread fit can easily be upset by the natural forces inherent in greasing.
3) Some foreign thread fits on foreign implements are poor to start with and on some there is the added problem that the shape of the fitting will not seal in an American grease gun. One notices that these fittings get sloppy and spin right out as soon as they back away from their seat. These fittings should be removed and labelled well if saved so that you or a family member does not give them to someone not already an enemy. Replace them with a fitting that fits snuggly and begins resisting after the 1st turn in. You may not be able to seat this fitting but it will resist turning out.
4) On things that bang a lot like bushog PTOs even taper fittings will sometimes back out with years of neglect.

If any fitting does not begin resisting before it seats I recommend you use loctite #638. This is a very strong formulation that loses a lot of its strength at boiling temperature and can be easily removed by heating. Characteristically, a loctite joint will resist all the way out even on a loose thread. This gives time to notice the fitting is loosening before it gets away!
Larry

 

[BATTY54]

Is there actually a metric pipe thread? I can only find NPS or NPT taps and fittings with NPT thread and metric heads.

 

[wrenchturner]

I have had grease fittings to come loose due to the hole being stripped. The loctite is a good idea but be sure to clean the surface with brake cleaner to remove all oil. Also, loctite makes product called Sleeve Reatiner which might be the # 638. Also, sometimes I have tightened the hole by using a tapered punch and peening around the hole. You can do this with tapered thread fittings.

 

[3RRL]

If those fittings just fell out and the threaded holes are still OK, Napa sells a zerk fitting kit with a bunch of different threads on them for about $7 bucks. You might find ones that fit better...and use the locktite anyway.