shop press puzzle

jmc · Nov 20, 2009

Hello,

I volunteered the TBN brain trust to help a friend disassemble his (imported) 5 ton hydraulic press cylinder, picture attached. It's a single acting cylinder with an internal spring return. The picture shows the cylinder with the end completely unscrewed, and a pair of shims holding the rod out against the internal spring pressure. Obviously there could be a lot of different designs for these things but based on what you've seen in the past:

Question 1- Is the stop collar (sitting on top of the shims) assembled to the rod with a press fit or is it threaded?

Question 2- Is the return spring a compression spring on the rod side of the piston or a tension spring on the pressurized side of the piston?

Question 3- Will this be difficult to reassemble because of the spring tension?

Thanks,

John

AKKAMAAN · Nov 21, 2009

jmc said:
Hello,

I volunteered the TBN brain trust to help a friend disassemble his (imported) 5 ton hydraulic press cylinder, picture attached. It's a single acting cylinder with an internal spring return. The picture shows the cylinder with the end completely unscrewed, and a pair of shims holding the rod out against the internal spring pressure. Obviously there could be a lot of different designs for these things but based on what you've seen in the past:

Question 1- Is the stop collar (sitting on top of the shims) assembled to the rod with a press fit or is it threaded?

Question 2- Is the return spring a compression spring on the rod side of the piston or a tension spring on the pressurized side of the piston?

Question 3- Will this be difficult to reassemble because of the spring tension?

Thanks,

John

I have never opened one of these before, but I give you some input that I think is possible...It is hard to tell when one dont have the hands on it, but take it as is......

Answer 1- The stop coller is not made to come off. The spring and the rod will come out in one unit. Spring will come off after taking apart piston from rod.

Answer 2- I go for the first alternative, compression spring on the rod side.

Answer 3- Depends on the design of piston and rod connection. But think about manufacturing process, it must be made so it is somewhat easy to assemble in manufactoring.....I wouldn't say chinese are lazy, but they are smart enough to make an easy day at the factory.....

Anyway keep unscrewing that threaded thing around the rod and pull it out....and please tell us whats happening...more pics please.....
Thats my 2 cents....

Wayne County Hose · Nov 21, 2009

I would be extremely careful disassembling this. Personally, in my shop, I don't take these in for repair. I like my head to stay on my shoulders where it is now. I have seen these things fly apart and destroy anything in it's path. For a lot of these, they have a jig that they lock it into for assembly.

jmc · Nov 22, 2009

OP here. Thanks for the replies. He decided to take it to a hydraulic shop to see if they could fix it economically (since it's an inexpensive press to begin with).

It would have been nice if everything disassembled as a unit but with the end completely unscrewed, they were still under spring tension.

John

AKKAMAAN · Nov 22, 2009

jmc said:
OP here. Thanks for the replies. He decided to take it to a hydraulic shop to see if they could fix it economically (since it's an inexpensive press to begin with).

It would have been nice if everything disassembled as a unit but with the end completely unscrewed, they were still under spring tension.

John

good, please keep us updated about how it was internally designed...

Brad_Blazer · Nov 24, 2009

Check out page 11 here:
http://www.harborfreight.com/manuals/94000-94999/94681.pdf

If the spring goes between pins 6D and 15D, it looks like you would have to remove the bottom nut, rotating the cylinder in unison to avoid twisting the spring, then remove pin 15D to release the spring.

jmc · Nov 25, 2009

Brad,

Thanks for the research. In the meantime, he found the cylinder manual and called the manufacturer. Their technical support said the cylinder was not repairable and a replacement is $180. (He only paid $200 for the WHOLE press in 2005, w/ free shipping.) We're waiting to see the hydraulic shop's response.

John