Torque Values for Retaining Rings?
Torque Values for Retaining Rings?
(OP)
Does anyone have a good reference for acceptable torque values for retaining rings?
For fasteners it is pretty straight forward to calculate the stress on the screw for a given torque, and there is a lot of information online about it also. An example is on this site:
Link Some of our screws are vented, and we just calculate the new cross sectional area (because of the vent hole in the screw) of the screw and then this changes the stress (F/Area).
One of my colleagues mentioned (jokingly) that a retaining ring is just like a screw with a large vent hole.. I think that the limiting factor for retaining rings will be the stress in the threads and not the axial stress in the cross sectional area of the retaining ring. I am not sure how to go about calculating what we should use for torque values.. We were thinking of getting a force gauge and just testing it ourselves. Any body have ideas?
For fasteners it is pretty straight forward to calculate the stress on the screw for a given torque, and there is a lot of information online about it also. An example is on this site:
Link Some of our screws are vented, and we just calculate the new cross sectional area (because of the vent hole in the screw) of the screw and then this changes the stress (F/Area).
One of my colleagues mentioned (jokingly) that a retaining ring is just like a screw with a large vent hole.. I think that the limiting factor for retaining rings will be the stress in the threads and not the axial stress in the cross sectional area of the retaining ring. I am not sure how to go about calculating what we should use for torque values.. We were thinking of getting a force gauge and just testing it ourselves. Any body have ideas?





RE: Torque Values for Retaining Rings?
When you use a retaining ring to secure a component in a pocket, you are basically using whatever housing design is present as the tension member in the system- the retaining ring functions as a nut would, and is governed by the same rules- failure is controlled by shear stress in the thread, not axial stress in the main body (as you have already stated).
If the goal is to apply accurate preload with a retaining ring, you have a tricky problem on your hands- because to do that, you really need to know how stiff your enclosure or housing is along the axis through which the ring applies tension. You can get half way there by calculating simple applied forces due to torque and the thread pitch, but it's also important to remember that a retaining ring usually has very large diameter threads, so frictional losses are much, much larger than they would be for a nut-and-bolt assembly, meaning that the simple calculation method is not going to be accurate.
The simplest way is *probably* to measure directly, using either a force gauge, or measuring the change in length of a part based on torque applied to the retaining ring- with the caveat that this 'test part' must be simple enough that its strain rate can be very easily and accurately calculated.
RE: Torque Values for Retaining Rings?
RE: Torque Values for Retaining Rings?
I've done some calculations on retaining rings and yes I've based it on the threads being sheared.
Formula's for thread shearing can be found at http://www.roymech.co.uk/Useful_Tables/Screws/Thre....
Now regarding the axial load I've used the general formula F= T/(0.2*d) and ignored the hole in the centre of the ring.
So basically in my application the retaining ring is holding a plug in place which is subject to pressure on one side, so step 1 I calculated the axial force on the plug from the pressure and then used this force to stress the threads using the formula on the roymech site above.
Finally I used F= T/(0.2*d) to determine the minimum required torque for the ring.
hope this helps
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein