Dipper ram developed a leak so took it apart to seal it. The piston is threaded onto the rod with a set screw to hold it. When I took it apart I was surprised when the piston started to turn when I was loosening the set screw. I have the factory manual & parts book, neither show a cylinder like this one although they seem to have a dozen different cylinders in the manual. So today I replaced the seals and putting it back together. Threaded the piston on and it stopped at just hand tight at the spot the allen lines up with the divot in the rod. Is this as tight as it needs to be? Doesn't seem right but that's the way it was before. This cyl has been off before at some time, looks as if it is the only one that's been off. Should have ot a shot of the piston, sorry. So, is hand tight tight enough? Or should I put the crank on it? Joe H
Don't know that ** but I do not thank any screw on piston should be free on the rod. That will allow it to bypass some fluid and hammer the threads leading to failure.
Unless it's something that's not like anything I've ever seen... tighten it according to the torque recommendation of that size thread for a grade 8 bolt, several hundred ft lbs.
Hard to tell from the closeup pic... is there something that seals the piston to the rod? like an o-ring groove.... if not then I would definitely put some torque on it like Delmer suggests. I am assuming in the closeup pic that dimple is where the setscrew was set.... I haven't done a lot of cylinders but all the ones I have done always have had the piston nut secured pretty tight.
It looks like the indent for your set screw is oblonged also, probably from the piston not fitting tight. I would tighten it like said above, but I would also drill a new indent for your set screw. It would only need to be about an 1/8th inch deep.
Gonna have another look at it today. Right now it's hand tight but bottomed out metal to metal. I don't know if I can turn it far enough to get past the existing dimple. And yes, it is a bit elongated . And yes, there is an o-ring in the piston to seal it. Joe H
I think you have two options for the allen head socket set screw. Tighten the piston to it's final position and drill a deeper detent in the rod. It will require a longer socket head set screw and Loctite. Or you can drill and tap a new hole in the piston, thread it and then drill a new detent in the rod.
If the metals bottomed out and there's an O ring I'd say that's adequate the reason for the set screw is so you don't require high torch to keep it from backing off and like suggested lock tight on the set screw.
I put the crank on it and got no movement. It's metal to metal & isn't going any further. Locktited the allen and put if back together. I'll see what happens tomorrow, no more leak I hope. I did find a similar cylinder in the ** manual, says it fits another machine but same design. Said tighten piston to 1150 ft pounds, allen screw & locktite. I'm light on the torque but the allen was back where it came apart so I'm done. Joe H