Straightening a hydraulic cylinder rod (JCB 212s, backhoe bucket cylinder)

OK some success. I did the other side front curl cylinder, and besides a stuck rod pin (not the small piston pin) everything went well. The piston pin came right out.
Today I did the rear bucket curl cylinder, the one that was bent. I managed to straighten it a fair bit, it's not perfect. I got it from this:



To this:



This is the setup, I set it on some blocks of wood with a half circle cut out, that I had laying around, 20 ton press. Used a piece of aluminum to press on the bar.



Before cranking down on it I threw some 1" plywood on either side so if things went sideways the big chunk of steel didn't come flying at me

Most of the bend was toward one end. So I had to reposition it, this was the final try.


Went up to about 9 US tons. Unfortunately I can not report yet if it worked. The cylinder is back together but I'm still trying to fix my screw up from last week. I have to take that rod to a machine shop to get the remaining pin drilled out. I haven't been able to do it. It's hardened and my drills just dull.

you don't give up easy, get some masonry bits and sharpen the carbide to a little sharper point, those will wear through nearly any steel.

greg9504 said:

Today I did the rear bucket curl cylinder, the one that was bent. I managed to straighten it a fair bit, it's not perfect.

Click to expand...

There is an out-of-straightness tolerance specification for cylinder rods. They don’t have to be absolutely straight. I can’t remember what it is off-hand but can look it up if you like.

Your battle is real, the shop I brought my 212s slew cylinder to for rebuild ended up just drilling the pin out and threading it for a grub screw. Took them an extra hour but I figure that was better than the day I would have spent cussing at it.

Latest update, 2 broken end mills and one broken center punch later, and the broken bit of pin has been drilled out. The cylinder is back together.

However it's another case of one step forward, two backward. More on that later...

OK so everything is back together now. All 3 cylinders were 40mmx70mm and used the same seal kit. The kit had an extra o-ring that I couldn't figure out where it went, so I just figured it was a generic kit and that I could ignore the extra piece... until I was assembling the last cylinder. Then I finally figured it out. It was a backup ring. I stupidly assumed that "if 3 things come out, only 3 should go back in". Plus the parts diagram only showed 3 seals: large 0-ring, the scraper at the top and then the inner oring.


While assembling the last one (the one with that had the broken pin) I noticed that the "extra" ring fit perfectly within the top of the inner o-ring, and it was made of a harder material. I'm guessing it was a backup ring. So I had to completely disassemble the 2 other cylinders I had already completed to put the ring in. It was even colour coded Doh!

At least I hope that is what it was for, seems to fit perfectly. Any job worth doing, is worth doing twice

Yep, that’s exactly where they go.
Great job.