Kubota M62 TLB Pin Retaining Bolt Snapping / Loose Nylon Lock Nuts

[JenniferKubotaM62]

Fellow Kubotan's.....

I made this video for a friend (named Darrell obviously) at the last minute and had no plans to put on YouTube so forgive the poor camera skills and narration. After giving it some thought, I feel others may benefit from it. It sure woke my eyes up to how quickly a very heavy part of your tractor can be laying on the ground looking up at you while you search the yellow pages for crane rental 2 hours from the closest SMALL town.

Jennifer

 

[RedNeckGeek]

Fellow Kubotan's.....

I made this video for a friend (named Darrell obviously) at the last minute and had no plans to put on YouTube so forgive the poor camera skills and narration. After giving it some thought, I feel others may benefit from it. It sure woke my eyes up to how quickly a very heavy part of your tractor can be laying on the ground looking up at you while you search the yellow pages for crane rental 2 hours from the closest SMALL town.

Jennifer

Thanks for the heads up!!!

My last tractor, a Kubota L3240, broke those bolts frequently on the FEL. I wasn't very good at keeping up on greasing the pivots, and I think that had a lot to do with why they were failing. The M62 has a big sticker on the backhoe telling you to grease those pivots every 10 hours. I'm coming up on 300 hours, and have been doing my best to honor that 10 hour commitment, and so far at least, I haven't seen any broken bolts.

Stepping back a bit, though, we ask a lot of these machines, and being mechanical in nature, they're not perfect. That same 10 hour interval gives us a chance to find things going sideways before they land us in real trouble. Doesn't always help, but it sure is a step in the right direction. Before I make my next trip into town, I'm gonna take an inventory of the size of those bolts on the M62, then drop by Tractor Supply and lay in a few spares. Maybe even spring for Grade 8 versions...

That Cat I'm taking so much crap about weighs twice what our M62s do, and it suffers from the same issues, and more. It's all part of the deal. The neighbor that owns it has some real horror stories about its failures, and I'm happy to help him out with a little shop time when he comes knockin'. That kind of "you scratch your back, I'll scratch yours" goes a long way in keeping our machines workin' hard for all of us.

 

[JenniferKubotaM62]

Thanks for the heads up!!!

My last tractor, a Kubota L3240, broke those bolts frequently on the FEL. I wasn't very good at keeping up on greasing the pivots, and I think that had a lot to do with why they were failing. The M62 has a big sticker on the backhoe telling you to grease those pivots every 10 hours. I'm coming up on 300 hours, and have been doing my best to honor that 10 hour commitment, and so far at least, I haven't seen any broken bolts.

Stepping back a bit, though, we ask a lot of these machines, and being mechanical in nature, they're not perfect. That same 10 hour interval gives us a chance to find things going sideways before they land us in real trouble. Doesn't always help, but it sure is a step in the right direction. Before I make my next trip into town, I'm gonna take an inventory of the size of those bolts on the M62, then drop by Tractor Supply and lay in a few spares. Maybe even spring for Grade 8 versions...

That Cat I'm taking so much crap about weighs twice what our M62s do, and it suffers from the same issues, and more. It's all part of the deal. The neighbor that owns it has some real horror stories about its failures, and I'm happy to help him out with a little shop time when he comes knockin'. That kind of "you scratch your back, I'll scratch yours" goes a long way in keeping our machines workin' hard for all of us.

I'm religious about the 10 hours, mainly just because it's so much fun using the Milwaukee cordless grease gun. What blew me away is that for that bolt to clean sheer would have required a lateral rotational force ON the pin of such high amount, it must have been dry and the boom grabbed a dry spot on the pin and grabbed on. I bought it with 50 hours on it, it was a rental from the local dealer but you never know how much they greased it.. just always assumed that pin would be so locked down it wouldn't rotate. I was going to get grade 8's as well but the Homeless Despot (the only hardware store within 100 miles) only had those.. Now that I'm aware, I'll watch them close, they only really do keep the pin from leaving the boom so should be ok as grade 5 (which I assume they are).

The cheap Chinese slave labor nylocks backing off was a surprise as well, normally I hate those things cus they gall and lock up so tight you need to chisel them off, not loosen by themselves... That all being said, it's obviously good practice to check all those post delivery (which I did, they were all snug) and continue to on a regular basis.

Item 40 below is the little snapper....

 

[TMGT]

The nuts shouldn't be overly tight, you want some play so the bolt can actually "float" a little for the slight pin movement, the bolt being too tight can actually cause it to break easier.

The broken bolt on the boom was possibly caused by catching the bottom and breaking it or as you said a dry pin, if it was dry enough to cause that you might want to check for damage. Being a rental who knows how it was treated in those 50hrs, the boom has a lot of weight and takes a lot of cyclic loading so a dry pin could cause problems.

If your replacment bolts are stainless I can't tell the grade from the video, if they are just zinc plated then they appear to be grade 2 due to no making on the head.

 

[JenniferKubotaM62]

The nuts shouldn't be overly tight, you want some play so the bolt can actually "float" a little for the slight pin movement, the bolt being too tight can actually cause it to break easier.

The broken bolt on the boom was possibly caused by catching the bottom and breaking it or as you said a dry pin, if it was dry enough to cause that you might want to check for damage. Being a rental who knows how it was treated in those 50hrs, the boom has a lot of weight and takes a lot of cyclic loading so a dry pin could cause problems.

If your replacment bolts are stainless I can't tell the grade from the video, if they are just zinc plated then they appear to be grade 2 due to no making on the head.

Great points, I'll probably back off that lock nut a bit, it's floating but could be a bit looser. I'll probably source some grade 8's at some point but I was torn between "do I want to make a cheap bolt harder to break and risk damage to the boom ect or do I want to consider it a cheap pseudo sheer bolt and just keep an eye on it and have some as backup" personally I'd rather sacrifice the occasional cheap Home Depot bolt than risk damage to the Kubota boom etc. . I didn't even look at the head, if I recall my apprenticeship with Detroit Diesel Allison, the number of slashes on the head plus 2 is your grade (6 slashes is a grade 8) but I may be mistaken, it's been a while.

 

[RedNeckGeek]

FWIW, that Cat I've been working on uses a steel tab welded to the end of one of the pivot pins that holds on the curl cylinder of the FEL. The tab has a hole drilled in the other end that fits over a stationary pin to keep the pivot pin from rotating. A snap ring on the other end of the pivot pin keeps it from falling out. Somehow, the tab had broken the weld between it and the pin, and the pin came out far enough that the bucket wouldn't curl anymore. The lost plate was made from 1/4" steel, the pin was somewhere near 1 1/2" in diameter, and a plug weld was used to hold the plate to the pin. The weld failure was progressive, meaning that the fracture surface was dirty and rusted, showing it had been cracking for a long time. So something is causing the cylinder to impart a torque to that tab. The owner is religious in applying moly grease to his machine, so it's not a lubrication problem. Then again, the forces that huge backhoe puts on that cylinder are far beyond what an M62 is capable of, so who knows what that tab really sees. Maybe that's why Cat used a tab and not a bolt through a boss like Kubota does on the M62?

 

[JenniferKubotaM62]

Well I checked out the snapped off bolt head (I still had it) and also checked another that I had pulled that had not snapped yet but I wanted to be safe (and compared it to the spot it was in). You can clearly see that grease does not get in that passage on the end of the pin, and they way it's designed, in motion it just scores and scores the bolt till it eventually snaps. The marking on the head is .7 which would imply with metric grade indicators that its around a grade 5 but with that scoring, and the remaining head piece I have left, it looks like it just scored the outside and then snapped, no twist markings on it etc.... you can see it wiped the threads right off and even bent it a bit, you all may want to check yours for score marks. They need to countersink/chamfer the rod shaped hole that goes across the pin as it's obviously stronger metal than the bolt and has spurs on their drilling.

Jen

 

[JenniferKubotaM62]

FWIW, that Cat I've been working on uses a steel tab welded to the end of one of the pivot pins that holds on the curl cylinder of the FEL. The tab has a hole drilled in the other end that fits over a stationary pin to keep the pivot pin from rotating. A snap ring on the other end of the pivot pin keeps it from falling out. Somehow, the tab had broken the weld between it and the pin, and the pin came out far enough that the bucket wouldn't curl anymore. The lost plate was made from 1/4" steel, the pin was somewhere near 1 1/2" in diameter, and a plug weld was used to hold the plate to the pin. The weld failure was progressive, meaning that the fracture surface was dirty and rusted, showing it had been cracking for a long time. So something is causing the cylinder to impart a torque to that tab. The owner is religious in applying moly grease to his machine, so it's not a lubrication problem. Then again, the forces that huge backhoe puts on that cylinder are far beyond what an M62 is capable of, so who knows what that tab really sees. Maybe that's why Cat used a tab and not a bolt through a boss like Kubota does on the M62?

I much prefer the way Kubota does it, it was an easy fix to do on my part.

 

[TMGT]

Well I checked out the snapped off bolt head (I still had it) and also checked another that I had pulled that had not snapped yet but I wanted to be safe (and compared it to the spot it was in). You can clearly see that grease does not get in that passage on the end of the pin, and they way it's designed, in motion it just scores and scores the bolt till it eventually snaps. The marking on the head is .7 which would imply with metric grade indicators that its around a grade 5 but with that scoring, and the remaining head piece I have left, it looks like it just scored the outside and then snapped, no twist markings on it etc.... you can see it wiped the threads right off and even bent it a bit, you all may want to check yours for score marks. They need to countersink/chamfer the rod shaped hole that goes across the pin as it's obviously stronger metal than the bolt and has spurs on their drilling.

Jen

How many hrs are on the machine? Those bolts look awfully dry and clean, the grease doesn't need to reach the bolt, but anything with some hrs that's been greased properly will most likely show up on that bolt from my experience.

That bolt should see very little load on a properly greased machine that isn't abused. In order to shear a bolt that size something is wrong.

 

[JenniferKubotaM62]

How many hrs are on the machine? Those bolts look awfully dry and clean, the grease doesn't need to reach the bolt, but anything with some hrs that's been greased properly will most likely show up on that bolt from my experience.

That bolt should see very little load on a properly greased machine that isn't abused. In order to shear a bolt that size something is wrong.

I bought it from the Kubota dealer at approx 50 hours and noticed it before my first grease which would have been at 60 hours but to answer your question, I think I'm at 175 hours right now. They had it in their rental fleet for the first 50 hours of it's life and I agree, it does not appear that any grease has ever gotten down to that area but when greasing, it just keeps coming out the other end so there may not even be a grease channel to that area, I may pull them out and manually grease them.