Grease Fitting Zerk nipple size

[Janat83]

The grease fitting on my left main as shown in the picture was broken, I couldn't locate the right part number, I got 2 different parts from aircraft spruce that didn't match as shown in the pictures, your help is much appreciated. 

1968 M20C manual gear 

[Guest]

It’s part of item 29.

[PT20J]

1 hour ago, M20Doc said:

It’s part of item 29.

Clarence, it looks like Frank put a couple of comments in the pdf file — anything pertinent?

Skip

[Vance Harral]

An Alemite 3018 matches the spec of the original zerk, e.g. https://locknlube.com/products/alemite-3018-grease-fitting-6-40-unf-2a-threads.  But let me share the bad news on why you're missing it in the first place.

If you use an extractor to get the old, broken zerk shank out, you can carefully install a new one (maybe after cleaning up the threads with a 6-40 tap); at which point there's at least a 50/50 chance the new one will immediately strip out - moreso if the threads in the bearing itself are buggered.  The amount of torque these fittings will take when brand new is very small - basically finger tight.  Don't be surprised if the new zerk doesn't really set up, and/or pops out as soon as you try to put a grease gun fitting on it.

Assuming you can actually get decent purchase on the threads, there's about a 50/50 chance you'll thence break off the zerk when trying to apply grease, and thereby wind up in the same situation as before.  These tiny zerks are soft and fragile, and won't take much side pressure at all before they snap off - you need to be extremely careful when putting a grease gun fitting on them.  A lock-n-lube tip helps, but isn't a panacea.

Assuming you actually get the new zerk installed, it doesn't strip, and you don't break it off when applying grease, congratulations... but you'll get the opportunity to break it or strip it out again at the next annual.  It will definitely get stripped or broken if a mechanic does the work who doesn't understand how fragile these things are.  After a couple of annuals, you'll likely lower your standards, and just jam a needle tip grease gun fitting in the empty hole like everyone else.  That doesn't work very well, but it's still better than actually trying to use the tiny, under-designed zerk.

If you're really serious about greasing that bearing, it's actually easier in my opinion to remove the landing gear to do so, than to actually push grease through the designed zerk without it popping out or breaking off.    The whole thing is just badly designed.  It's my understanding that later model Mooneys use larger, pound-in zerks.  Sometimes people try to install these compression zerks into the threading fittings of the older models, and that just makes everything worse.

I love my Mooney, but certain small details about it are just poorly designed, and this is one of them.

 

[Guest]

7 hours ago, PT20J said:

Clarence, it looks like Frank put a couple of comments in the pdf file — anything pertinent?

Skip

The foot notes don’t appear in the manual, that I have at home.  I’ll check another at work.

Clarence

[47U]

13 hours ago, Janat83 said:

1968 M20C manual gear 

I was able to remove the zerk remnants with a tire/tube valve stem tool.  Since then, I’ve been using a flush fitting to grease the forward trunnion.  It works best while the airplane is on jacks so you can unlock the gear and it’s free to move while you inject the grease.

[Janat83]

Thank you guys for your comments, looks like it's not direct replacement part, I'll share your comments with my mechanic and see what he want to do. 

Best Regards 

MOUSTAFA 

[PT20J]

2 hours ago, Janat83 said:

Thank you guys for your comments, looks like it's not direct replacement part, I'll share your comments with my mechanic and see what he want to do. 

Best Regards 

MOUSTAFA 

Some models used a Alemite 3018 threaded fitting and some used a 3019 press in fitting. That’s why I asked Clarence about the notes. Mooney no longer updates these manuals and rolls the revision with changes. Instead Frank Crawford adds notes to the pdf files with corrections and changes. So, you really need the latest pdf to make sure you have all the current notes. 

Skip

[EricJ]

If a threaded fitting is missing or broken off, or a press-in fitting fallen out (or broken off), there are some grease gun adapters, e.g., a needle or a flare tip or a soft tip, that give you a fighting chance of injecting grease as long as the bearing isn't too clogged up.   It might be a sort-of-last-resort, or if it works it might be a reasonable way to get it done without having to wait for another fitting.    Might be worth a shot in a pinch if it helps.   

 

[Janat83]

16 hours ago, EricJ said:

If a threaded fitting is missing or broken off, or a press-in fitting fallen out (or broken off), there are some grease gun adapters, e.g., a needle or a flare tip or a soft tip, that give you a fighting chance of injecting grease as long as the bearing isn't too clogged up.   It might be a sort-of-last-resort, or if it works it might be a reasonable way to get it done without having to wait for another fitting.    Might be worth a shot in a pinch if it helps.   

 

I used the fitting from the other side to do it this year, but I definitely need to find a solution as the other one might get broken as well from being removed multiple times, taking the broken thread wasn't easy and took at least 2 hrs, very tight place. 

[N201MKTurbo]

I bought the Lock n Lube grease adapter set. It has grease needle that is about 1/8 inch in diameter with a tapered nose. It forces grease into the hole perfectly. Better than with the zerk.

https://locknlube.com/collections/greasing-accessories/products/narrow-needle-nose-dispenser

 

Edited June 21, 2022 by N201MKTurbo

[Pstone]

If you are going to clean up threads, use a thread-chaser.  A tap cuts in new threads, thread-chaser cleans up the current threads.

 

Pat