Help identifyiny hydraulic cylinders with dutch keys.

[midlifecrisis]

I have a John Deere 690 excavator that has non-JD boom/mast cylinders. The piston is secured to the rod with a dutch key. I removed the bolt and tried to unscrew the piston from the rod with no avail. I'm 99% sure the piston is treaded on to the rod. If anyone has experience with this setup, I would appreciate any info. Any torque specs, thread size/pitch, LH/RH, was Loctite used, mfg of cylinders, etc.

 

[wdchyd]

Pix??

I've seen them with keys

 

[midlifecrisis]

Thanks wdchyd, I really want to try narrow down the mfg so I can order repair parts. Every schematic for every mfg I've looked at so far uses a large nut to hold the piston to the rod. I also need to remove the piston from the rod for further repair. If I find out who made it I will have a better chance to fix it.

The machine is at my farm about 80 miles from me and I didn't take any pics. Maybe next trip.

 

[wdchyd]

If JD parts don't fit then you'll be visiting a local hyd shop to match seals. Not sure your gonna have any better luck than that.

JD 690 has different series of cylinders, some with keys

 

[Tractor Seabee]

leaning on 60 year old experience I am not sure about the term "Dutch Pin" I believe it is what we used to call an axial pin, if that is the assembly technique then you need to look for that pin and figure out how to remove it. Some I saw had a threaded end you could put a nut on and pull with an impact puller. Get those pictures.

LOL, Ron

 

[midlifecrisis]

Thanks Ron, you are correct, a Dutch key (or Scotch key) is an axial key. This particular one had an allen head bolt screwed into the end of the piston/rod. It was simple to remove. My problem is removing the piston from the rod. I'm guessing the piston is threaded onto the rod but not sure. I tried removing the piston with the limited tools and equipment I had with me, to no avail. I need the piston off the shaft so I can remove the cylinder head to replace the gland seals in the head. The yoke has been welded to the rod so the only way to replace the seals is to remove the piston from the rod. This sounds a little confusing and I hope you can understand the predicament I'm in. We just got snow and cold so this project might be delayed a bit.

 

[Tractor Seabee]

Thanks Ron, you are correct, a Dutch key (or Scotch key) is an axial key. This particular one had an allen head bolt screwed into the end of the piston/rod. It was simple to remove. My problem is removing the piston from the rod. I'm guessing the piston is threaded onto the rod but not sure. I tried removing the piston with the limited tools and equipment I had with me, to no avail. I need the piston off the shaft so I can remove the cylinder head to replace the gland seals in the head. The yoke has been welded to the rod so the only way to replace the seals is to remove the piston from the rod. This sounds a little confusing and I hope you can understand the predicament I'm in. We just got snow and cold so this project might be delayed a bit.

Mid- I am not a cylinder repair expert. especially older stuff. Do you have a hydraulic shop close by. They will probably be able to help you. I often take things to the experts. Winds up costing less than you think and gets rid of the hassle factor. The guys I go to are very helpful even if they don't get much $ out of it. I get accessories and fittings from them whenever I need to. If I had your cylinder that is where it would go. They are good at matching up internals on non-identifiable cylinders and other parts.

LOL, Ron

 

[Nutria57]

I had the same issue of getting the piston off a 2" rod. I removed the allen screw and attempted to unscrew. I ended up using heat and giant pipe wrenches. Finally got it off and discovered it had a second allen screw in the same hole as the first one. Thats right, a screw on top of a screw. If I would have taken the second screw out I bet the piston would have easily unscrewed off.

 

[stuckmotor]

Nutria57
Were the allen screws used like jam nuts?

 

[Nutria57]

Nutria57
Were the allen screws used like jam nuts?

Well, at first after removing the first screw I incorrectly assumed the screw kept the piston from rotating (coming unscrewed) while being used. I never thought to look down in the hole or run the allen wrench back down in there to check. Either the assembly folks had extra set screws and put a second one in or maybe by design acted like a jamb nut, either way I backed that sucker off with heat and brute force. And yes, the threads on the rod were all chewed up. There was enough left to chase them and put the piston back on fortunately.