Cylinder piston/rod bolt torque values

[DirtyHoe]

Greetings,
I was helping a friend rebuild a boom cylinder on a 580D. The bolt is a 1 inch grade 8 fine thread. The service manual says on page 4090-3 to torque the piston bolt to 475-525 foot pounds. But the general torque values on page 1051-2 says the grade 8 bolt should be torqued from 900-1100 foot pounds. Why such a big difference especially since this connection is prone to coming apart? Also should I use some blue loctite for extra insurance?

Thanks,
Steve

 

[DirtyHoe]

Those page numbers are out of the 580C manual, but the 580D manual(page 1001-5 and 8090-3) has the same torque values.

 

[Tinkerer]

I think that a dry threaded bolt has a much higher torque value than a lubricated one,as much as twice the torque. Locktite would be considered a lubricant in that situation.

 

[Billrog]

The last boom cylinder I did called for 12,000 torque and black locktite. This was on a 580 CK .

The correct bolt is very important someone had used the wrong bolt it broke and my boom came down with a crash . I'd just put up a 45' power pole and fortunately nobody was injured.

 

[catskinner 10]

It should have had lock-tight on it previously.
I always use blue lock-tight when rebuilding a cyl. They left the factory with it.
You should have to use a little heat when removing to break the bond
If it was done properly before.
Tom

 

[mikebramel]

Yes always use the blue thread lock. Use the lower torque value. Using the higher value pre loads the bolt too much and you will end up like the broken one pictured

 

[DirtyHoe]

Billrog,
It looks like the broken bolt was a grade 8. What's the difference between the broken bolt and the correct one? The parts book specifies grade 8.

Steve

 

[John C.]

Judging from the crud on the broken bolt, it came out of a scrap bin or a cubby hole somewhere. Did it actually come out of the subject cylinder? Judging from the fracture pattern on the broken bolt I would guess that it wasn't seated on a hard washer with a bevel relief cut into the inner circle.

If I used thread locker on a bolt it was the red. The blue is meant for items that might need to be re-torqued in the future. The doesn't hold for a bolt operating inside a hydraulic system where so many other components can be damaged in the event of a failure. When there is a question about torque you always default to the factory specification. The same goes when replacing parts in critical components.

 

[jimg984]

bad bolt was threaded all the way, good bolt has a shoulder and is stronger

 

[Edward yeo]

Greetings,
I was helping a friend rebuild a boom cylinder on a 580D. The bolt is a 1 inch grade 8 fine thread. The service manual says on page 4090-3 to torque the piston bolt to 475-525 foot pounds. But the general torque values on page 1051-2 says the grade 8 bolt should be torqued from 900-1100 foot pounds. Why such a big difference especially since this connection is prone to coming apart? Also should I use some blue loctite for extra insurance?

Thanks,
Steve

If you are still interested look at page 5 for piston nut torque setting and gland head bolt settings.

https://sealum.com/pdf/full/CylindersFull.pdf

 

[Tinkerer]

Welcome to HEF, Edward !
Are you affiliated with Sealum ??
The torque specifications of a different cylinder manufacturer cannot and should not be used on a different one.
Every individual cylinder has torque specs recommended by the manufacturer that made it.

 

[Billrog]

The correct bolt, torch and black lock-tight was what I got from the 580 CK repair manual.

 

[Coy Lancaster]

What is this torque specs y'all are talking about? The bolts always torque to 2-4 grunts with a 3/4" breaker bar (depending on bolt size) and a five foot cheater pipe, with red loctite lol.

 

[Birdseye]

…seriously, you don’t have a 2500 ft/lb torque wrench in your toolbox ?

 

[Coy Lancaster]

…seriously, you don’t have a 2500 ft/lb torque wrench in your toolbox ?

Doesn't everybody

 

[JL Sargent]

I've built a doz cylinders and they all had to have the locktite cooked out of them with heat. That's the RED type. I use the RED to lock in the new installs too like John mentioned and I have not had a repeat. I think Black is akin to Super Glue. I haven't used that.

 

[Welder Dave]

I don't know if any OEM's use Nord Lock washers but seems hydraulic piston nuts or bolts would be a good application for them. Not affected by oil, don't need heat to remove and better for vibration than Loctite. They can be a little hard to remove sometimes because of their design but wouldn't need to remove them too often on a cylinder.

 

[Birdseye]

Nord Lock washers seem like an excellent alternative to using the various grades of Loctite. Need more information on the pros cons . I’m sure someone has tried them in this application of hydraulic rod to piston bolt. After reading about them, the only negative I can think of would be if the surface of the aluminum piston is too soft or the steel of the bolt is too hard/brittle, but I doubt either of these conditions exists is the case of a hydraulic cylinder .

 

[John C.]

A bolt used in a properly designed application and torqued to the design value will not come loose. A bolt coming loose is being stretched. They don't come loose by turning on their own.

 

[Birdseye]

The problem for most of us diy folks is that we don’t have access to the precession gear to set the torque accurately. Using thread adhesive that requires a ton of heat to disassemble isn’t particularly good for the steel. Those special Nord Lock washers seem like a good compromise.