Hydraulic cylinder gland nut thread problem
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  1. #1
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    Default Hydraulic cylinder gland nut thread problem

    I'm currently rebuilding all of the hydraulic cylinders on my Allis Chalmers forklift. Four cylinders for the three stage mast and two tilt, new packing, wipers and seals for all of them. On the very last cylinder, (of course) the gland nut tightened up all of the sudden, about half way from fully seated. This was after very careful cleaning, and a test running the gland nuts in with the threads oiled. But, on assembly, it would suddenly not tighten, and did not want to loosen either. Heat and oil made no difference, and the pin spanner bent. Not sure what happened, I had been pretty sure everything was very clean. Anyway, I accepted that there was going to be some damage, and put a 4' bar on a pipe wrench to spring the gland nut out. The damage is brutal. And the cylinder is a cluster of three that are a welded assembly, so not easily replaceable unless I hunt down a used one..
    So, on the gland nut I have used my lathe to trim off the damaged threads, and carefully cleaned up the lead thread. Because the cylinder assembly is massive and bulky, all I can do is make sure no more threads are loose or damaged. I have 7 full threads left, will this be enough to hold the gland nut on? I imagine if not, I could weld the gland nut on, and start the hunt for replacement cylinders..
    Thoughts? Anything else I should try?
    Attached Thumbnails Attached Thumbnails img_2426.jpg   img_2370.jpg  

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    I could be all wrong on this but I think 7 full threads should be fine. If I'm seeing it correctly, that nut has the wiper and seal for the rod as well as the guide bushing, but it's on the dead side of a single acting cylinder so it doesn't see any true system pressure, just the little bit that might sneak by the piston seal.

    The nut probably acts as the stop on full extension of that stage of the cylinder, but the shear strength of those remaining threads is pretty strong.

    That's my two cents on the deal.

    Stuart

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    That's the pits. About all you can do is try to repair the threads on the nut with one of these or grind it down for clearance. I have used a thread file and see this on You Tube. Thread Repair using the EZ Thread tool - YouTube Or take it off the shaft and clean it up as good as you can in a lathe. I have seen some use a brazing rod called Easy Flo, maybe you can braze up the threads. I would try to use the 7 good threads with some Teflon paste that you paint on to seal them. If you have a lot of time. Watch some You Tube shows. I would not weld on the nut. The nut sure seems to have a lot of pipe wrench marks on them....sighhhh Good luck

    PS. You may want to ask this in the welding forum too.

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    How are the threads in the barrel? I am thinking it will work just fine with what’s left. Skip the Teflon paste, the Oring does the sealing. Put some anti seize on the threads. MikeC might have a better idea he has a lot of experience.

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    Actually I think atomarc's reply is worth four cents and I agree with him. I've done plenty of them but usually on packer cylinders from the ass end of garbage trucks. They get beat to death. Fun! Some of those rams on fork trucks don't have a piston, just a stop ring. The head gland is generally the stop for the rod. I think just doing the best you can with the threads and you're good to go. Good luck.
    I'm going to try one of those easy threads. Thanks

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    Who is the guy that is a retired engineer from Prince Hydraulics? Damn, If I could remember his handle? Damn meds.
    Is there a way to search members by state? One of the few from South Dakota.
    JR

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    The threads left on that gland will be enough, a few less though and youd need a new gland.
    I would definitely make sure there are no burrs in the part you're going to be threading the gland into. That's probably why it locked up in the first place.
    And JRiowa, we actually just serviced some cylinders for Prince in Sioux city that were too big for their shop.

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    Quote Originally Posted by StinkyDan View Post
    The threads left on that gland will be enough, a few less though and youd need a new gland.
    I would definitely make sure there are no burrs in the part you're going to be threading the gland into. That's probably why it locked up in the first place.
    And JRiowa, we actually just serviced some cylinders for Prince in Sioux city that were too big for their shop.
    I'm the guy who worked in the engineering dept. at Prince. Looks like this is a single acting displacement style cylinder? If so, you will still see pressure on the gland side. Without seeing it myself, I wouldn't have a clue how to fix this other than machining a new gland. You could do that.

    Stinky Dan, Prince has 5 plants and a well equipped lab. The plant in Brookings has produced cylinders up to 14" bore, so they DO have equipment to handle the big stuff. What did you have to do on what?

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    R Dan, I taught a scraping class for Prince years ago. They set up their own rebuild shop with a Churchill Grinder. I think it was across the river in Nebraska? They set up the rebuild shop because they got ripped off by a rebuilder in Chicago. I believe the rebuilder went bankrupt while doing their CNC lathe in the shop and they had a heck of a time getting it back. Do you remember that?

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    So, first off thank you all for the input, it helps tremendously. Between cutting heavy angle on the old Kysor-Johnson bandsaw, I spent some time on the cylinder..
    So, for starters, yes this is a single acting cylinder as Ray Behner suggested, and only has a stop ring, so the gland nut will see full system pressure. I did inspect the internal threads, and there is a void about 5 threads down, where it seems a chunk of thread broke loose and started to cause damage. As I recall, it got a little stiff to turn, and might've gone a full turn farther before stopping completely. Backing it out is what required the pipe wrench, and is responsible for the ugly gouges..
    You can see the "pit/ divot" on the left in the pic, 5 or so threads down. img_2445.jpg
    So, even if I get the gland nut in, thats 5-6 good threads above the mess, thats keeping the gland nut on. More on that in a sec. I did with a die grinder and a little wheel manage to get the largest mangled bits of thread ground clear, and rinsed it clean. The gland nut will almost thread home now, about 6 turns in, and what looks to be 2 turns from fully seated. This is after removing the fubar (is that a technical enough term for PM?) bits from the gland nut
    img_2446.jpg
    I'm most concerned about the safety aspect of this: if it fails, it's most likely to happen with the heaviest load (4000lbs), and on a machine with a 15' mast, someone could very well be killed. So, if this all goes back together and doesn't leak, I'm pretty sure it's getting welded on. My thoughts are that three welds, maybe using some flat stock to bridge the gap where the tube meets the gland nut, so I'm not trying to make a hot weld directly over the o-ring.. thoughts?
    FWIW, I did make a few inquiries looking for a replacement cylinder. Not as hard to find as parts for the lunar rover, but it's going to take a while to find.
    Thanks for the advice this far.

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    I would not weld the gland, rather it might be worth remaking the gland from a 41XX steel, and ensuring the thread lenght is long enough for full engagement.

    If that's not going to be worthwhile, rebuild with what you have, then proof test the assembly with whatever method available to ensure the cylinder takes pressure to at least the highest load you'll be putting on it, and ideally 25%-plus over that.

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    Quote Originally Posted by badwithusernames View Post
    So, first off thank you all for the input, it helps tremendously. Between cutting heavy angle on the old Kysor-Johnson bandsaw, I spent some time on the cylinder..
    So, for starters, yes this is a single acting cylinder as Ray Behner suggested, and only has a stop ring, so the gland nut will see full system pressure. I did inspect the internal threads, and there is a void about 5 threads down, where it seems a chunk of thread broke loose and started to cause damage. As I recall, it got a little stiff to turn, and might've gone a full turn farther before stopping completely. Backing it out is what required the pipe wrench, and is responsible for the ugly gouges..
    You can see the "pit/ divot" on the left in the pic, 5 or so threads down. img_2445.jpg
    So, even if I get the gland nut in, thats 5-6 good threads above the mess, thats keeping the gland nut on. More on that in a sec. I did with a die grinder and a little wheel manage to get the largest mangled bits of thread ground clear, and rinsed it clean. The gland nut will almost thread home now, about 6 turns in, and what looks to be 2 turns from fully seated. This is after removing the fubar (is that a technical enough term for PM?) bits from the gland nut
    img_2446.jpg
    I'm most concerned about the safety aspect of this: if it fails, it's most likely to happen with the heaviest load (4000lbs), and on a machine with a 15' mast, someone could very well be killed. So, if this all goes back together and doesn't leak, I'm pretty sure it's getting welded on. My thoughts are that three welds, maybe using some flat stock to bridge the gap where the tube meets the gland nut, so I'm not trying to make a hot weld directly over the o-ring.. thoughts?
    FWIW, I did make a few inquiries looking for a replacement cylinder. Not as hard to find as parts for the lunar rover, but it's going to take a while to find.
    Thanks for the advice this far.
    The highest load it will ever see is when it stops at full extension. It will be taking the force of the full area of the bore x pressure.

    When its loaded with 4000 lbs, all that weight is on the rod. The gland is only seeing pressure on the area of the bore minus area of the rod, which will be WAY less force.

    Its not hard to get a rough calculation of the strength of the remaining threads if you know diameter and length of engagement. You can also calculate hydraulic force easily and see how safe you are. Count the turns of engagement or measure carefully. There may be 7 threads left with only 5 engaged. I would also avoid welding. Good luck with it.

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    I would not try to weld that gland in. It looks like, and probably is, ductile iron, so not suitable to weld. I would measure the dang thing up and make a new gland. Seal groove info can be had easily and use the old gland to compare. OP said it himself; that's a lot of gravity to be holding up with a sketchy work around. I can't see well enough in the pictures to tell if the tube ass'y threads are ok. When it's all said and done, I think I would be shopping for a used cylinder to replace it. I don't think I would want to trust it with half the threads gone. There is more than just the pressure to worry about; there is also the hoop stress in the tube ass'y threads.

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    Quote Originally Posted by Richard King View Post
    R Dan, I taught a scraping class for Prince years ago. They set up their own rebuild shop with a Churchill Grinder. I think it was across the river in Nebraska? They set up the rebuild shop because they got ripped off by a rebuilder in Chicago. I believe the rebuilder went bankrupt while doing their CNC lathe in the shop and they had a heck of a time getting it back. Do you remember that?
    Prince ran their own rebuild shop for quite a few years, but they quit doing their own rebuilding awhile back. I think it was a matter of being more than what they wanted to deal with anymore. I know at least one of the guys who was doing the work is still around there and they keep him pretty busy doing a lot of different things in their lab in South Sioux City, NE. They have a warehouse in Sioux City, IA, and they might have that Churchill stored there if they haven't sold it. I understand there is quite the collection of old used machine tools stored there.

    I remember talking to you about all this 5-6 years ago. I am retired, so I have no real idea what is going on around there now. As for the lathe, they did get it back after much effort.

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    Quote Originally Posted by R. Dan View Post
    I am retired, so I have no real idea what is going on around there now.
    Don't know about you, but I love that. I bet you know more than you think. About twice a month, somebody will stop by my place and their first words are "you won't believe this shit". I love hearing about it, but I'm sure glad that I don't have to deal with it.

    Thanks for coming on with some great answers.
    JR

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    Quote Originally Posted by JRIowa View Post
    Don't know about you, but I love that. I bet you know more than you think. About twice a month, somebody will stop by my place and their first words are "you won't believe this shit". I love hearing about it, but I'm sure glad that I don't have to deal with it.

    Thanks for coming on with some great answers.
    JR
    I stop in and see some of my retired friends, and I have to think back to when each one
    retired, to keep them up to date of the changes that have come after their time.

    Most times it ends with "You wouldn't recognize the place now"

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    This is wildly speculative (never done it, just came up with the idea). Could you do a reverse thread insert? Cut threads into the cleaned-up area and use something like a Time-Sert? Or would this just weaken the whole package?


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    Quote Originally Posted by bosleyjr View Post
    This is wildly speculative (never done it, just came up with the idea). Could you do a reverse thread insert? Cut threads into the cleaned-up area and use something like a Time-Sert? Or would this just weaken the whole package?

    Might as well just make a new gland if youre gona be making something like that

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    That gland nut is not that hard to make. I did one for my backhoe and it only took me half a day or so.

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    Make a new gland. There are enough good threads there.
    Keep the welder off of It.

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