SAE o-ring fittings - how tight?

[UncleBuck1]

This may be a dumb question, but I'd rather ask now than find out the hard way: when using SAE o-ring hydraulic fittings, how tight am I supposed to screw it in?

I'm not looking for torque settings (I could never fit a torque wrench under the hood of my tractor!), just whether I just make it snug on the 0-ring or really wrench it down and deform the o-ring.

 

[s219]

If manufactured right, the relief cut into the female side and the washer (or nut) on the male side will compress the o-ring to the proper amount when the washer/nut contacts the outer metal portion of the female side. So definitely get the washer/nut all the way down. From there, additional tightening only affects the threads, not the o-ring (it's already squashed the right amount between a rock and a hard place and isn't going anywhere).

For adjustable fittings, I normally snug the nut and washer down gently to compress the o-ring all the way in the desired position. Then give the nut an additional hard pull when I am sure everything is right and positioned properly. If you don't tighten enough, the fitting can rotate when hoses are moved/pushed, so you do need a pretty healthy wrenching on the nut.

The threads are the same as JIC fittings, which I also crank on pretty hard.

 

[s219]

Some good illustrations here, showing the o-ring fully squashed into that relief: http://pressureconnections.com/customer/prcoco/customerpages/literature/Steel_O-Ring_Boss.pdf

 

[kennyd]

A good "snug" usually does it for me.

 

[SPYDERLK]

Finger tight will not leak, but it will loosen with vibration and pressure cycling. Then it will blow out the oring. So tighten them up so youll never have to worry about it.
larry

 

[timster2]

Use silicone oring lube to help the oring seal on the fitting. No silicone use petroleum jelly and make the fitting tight. If subject to extreme vibration use some removable locktite on the threads

 

[Ford850]

Surplus Center has good specs listed for each fitting type. Here's the O'ring sheet. See the "alternate assembly method" if you don't want to use a torque wrench.
http://www.surpluscenter.com/images/techhelp/ORFS.pdf

 

[murphy1244]

A good "snug" usually does it for me.

Agree, you will feel it stop.