Torque spec on rings by Leupold or Nightforce - Dry or with oil?

Status
Not open for further replies.

Cowboybebop

Member
Joined
Jan 18, 2014
Messages
98
Location
East Coast, US
I have been torquing my rings to the spec provided by these companies with a drop of Breakfree CLP on the bolt threads. A friend of mine told me this method is incorrect, and I should reduce torque by ~30% when using lubricated threads, as the spec from the manufacturer is for DRY threads. Is this correct? Have I damaged anything?

Are the torque specs for scope rings for dry or lubricated threads?
 
dry as far as I know. if your Scopes are still working properly you probably haven't damaged anything you may have left ring marks on the tubes though.
 
It's confusing to me, because I watched a Leupold scope install video (from them), and the host showed that he added a drop of oil to the bolt when fastening the base to the receiver. He didn't mention the oil for the ring however. How do they expect us to know without it written down somewhere? Not to mention, wouldn't installing steel bolts into an aluminum ring cause dissimilar metal binding (galling)? Or degreased threads cause rust to form in the threads? It seems like some oil or lubricant should be used. Loctite also has a lubricant effect and I've never heard of anyone reducing torque while using that.

Keep the replies coming, this topic is driving me crazy.
 
I have always torqued dry or with Loctite 242. Aluminum and steel shouldn't be prone to galling. A dry stainless steel bolt in a dry stainless steel threaded hole is a perfect recipe for galling.

The strength of torquing is all the bolts having the same tightness.
 
Grease.

Threads tighten and hold - because they are flexed.

Torque - applied to dry threads - creates a lot of Friction, and will make the torque spec. long before deflection (and then rattle loose with vibration).

Grease - with a torque-wait-torque pattern - will have a very pronounced point of deflection, almost asymptotic.

They will tighten, and then quit moving without a very large increase of force.

And the grease, at film thickness, will act as a gasket to dampen vibration and spread the load across the thread.

It will also prevent corrosion seizing.




GR
 
Bear in mind that the lubrication of threads can be done wrong. I wouldn't recommend flying in an airplane or riding an amusement park ride that had Never-Seez applied to all the bolts when it was assembled.
 
I contacted a few companies and asked them this question.

Leupold: "lubrication has no effect on the torque values".
Trijicon: "torque specs are DRY, we do not have values for lubricated"

So now I wonder if I damaged my Trijicon MRO by mounting the plate to 12 inch-pounds with the screw threads covered in CLP.
 
What was the spec? 12 inch pounds is not very much, I would think you are Ok.
 
If you have been turning wrenches all of your life you get a good feel for tightening fasteners down tight enough but without thread damage/galling/screw stretching, but it is real hard to feel the difference between 10 in lbs and 12. A lot of people have no feel, even if they have been turning wrenches, and a lot of people simply don't do it, so torque values and a torque wrench of some sort is a real good idea. Even those with experience can benefit. Scope are expensive and we don't want to damage them, nor do we want them to slip. It is easy to over torque rings, very easy.

Sunex 10 to 50 In Lbs Torque Wrench Pic 2.jpg
 
Last edited:
Vortex recommends 15-18 inch pounds on scope rings.
I find this to be marginal in terms or holding a scope from moving.
I use 20 inch pounds on a rail and 20 on the scope rings.
Clean and dry the surfaces but do not lube, I do as stated previously add a TINY bit of blue lock tight on the base threads only.
My scopes don’t move.
J
 
borka and i think fix it sticks are popular brands of lightweight but reasonably high quality tools that are suitable for carrying in your pack or to the range.
 
i have the borka set that i bought from rifles only a loooong time ago. i don't have to use it on my own stuff too often but there's always someone at the range or match that needs help. they get used a lot
 
OK, let's talk about torque requirements.

As a nuclear engineer, though not a mechanical engineer in the field, torque requirements are essentially there to ensure proper bolt up and locking device (if any) engagement. These torque requirements may or may not actually approach the maximum design torque limit of the fastener itself. Maximum torque limits are established based on the size of the bolt and the material it is made from.

So, when a manufacturer designs something, they look at the fasteners, their location, what they're supposed to do and withstand, and they determine "this is the torque range required for this fastener to do its job properly". In real engineering drawings, these are typically dry torque values, unless the drawing itself required some sort of lubrication to be applied. In that case, it's a "wet torque".

In most commercial products, however, you don't get engineering drawings or technical specifications. What you get is, perhaps, a little booklet which says "Install this and torque to this value". Unless they TELL you it's to be lubricated in the instructions, it's a dry torque.

In the engineering world, to ensure proper minimum torque is applied to the fastener in order to acheive its design function of properly clamping components together, there are concepts which need to be applied and understood.

One is "running torque". This is the torque required to actually cause the bolt to turn. If a required bolt torque is 25 +/- 5 ft-lbs, this is the value to be applied to a bolt which essentially turns freely in it's threaded hole. However, if the fit is tight enough that it takes 5 ft-lbs of force to actually get the bolt to start torquing, then you run the risk of undertorquing the bolt if, for this example, you only apply 20 ft-lbs of torque. Since it takes 5 ft-lbs just to get the bolt to torque, this would mean the actual final applied torque to the fastener is really only 15 ft-lbs. So, in this case the PROPER torque to apply per the indication on the torque wrench would be running torque plus required torque, or 30 +/- 5 ft-lbs.

Then there's "dry torque" and "wet torque", which essentially mean "unlubricated" and "lubricated".

Then there are torque multipliers. Then there are special hollow core bolts designed to be preheated with an inserted heater prior to torquing, which dramatically increases the applied torque once the bolt cools back down to it's normal operating temperatures. (Reactor vessel closure head bolts, for example, are torqued this way resulting the the equivalent applied torque in the millions of ft-lbs.)

Damage or no damage?

With respect to the OP's question about backing off 30% for lubricated (wet) torque...this would ONLY be a requirement in this case if there were an actual technical requirement written somewhere. In other words, the instruction booklet contains words to that effect.

You will NOT cause any damage to the screws on your scope mounts by applying the full manufacturer's torque value because the fastener itself is designed to handle it based on its size and material strength. Wet or dry, ONLY if you exceed the material's design limits will it break. You MAY be more likely to leave a deeper mark in the material where the fastener tip is pressing against when you torque it, if it's that kind of fitting. If it's on a clamp ring, then all you'll be doing is getting a better clamp. You'll cause no damage.
 
Last edited:
I took mechanical engineering technology at Purdue a long time ago. We were taught that, in general, the threads should be lubricated to torque them.

A bolt actually holds by stretching lengthwise. Think of it as a spring that gets stretched and is pulling on the threads. A torque wrench actually measures the stretch of the fastener

Think about it. Why does a 3/4” bolt take more torque than a 1/2”? Because it takes more pulling force to stretch the bolt

Now, worst case suppose you have a bolt and/or threads that are rusty/dirty. You may apply full torque but not have enough turns to stretch the bolt. Anyone who has assembled a car engine knows you lube head bolts, at least that was our instructions back in the 60’s and 70’s

Or, as an acquaintance used to say “tighten it until the head snaps off, then back off 1/4 turn”
 
Last edited:
Keep in mind that adding a lubricant to the threads (CLEAN threads, mind you...) does other things than just make the metal parts slide across each other easier.

Lubricants are required for certain conditions/materials and sometimes it really has nothing to do with torquing, per se. Stainless steel components, for example, are extremely susceptable to galling with metal-to-metal contact. This is why lubricants such as neolube (colloidal graphite suspended in alcohol) are added to the threads. Tightening/loosening CRES (Corrosion Resistant Steel, or stainless steel) components initially causes microscopic galling of the thread surfaces. This rapidly becomes visible galling with repeated unlubricated use. Eventually it can get so bad that merely attempting to turn the bolt/component in either direction will literally cause pressure welding of the galled surfaces together.

Lubricants are also added as thread protection against future corrosion while installed. This makes them easier to remove at a later date without causing thread damage which must be repaired before reuse.

Since it was brought up, "torque" isn't the force which holds the bolted components together. It's bolt tension felt between the angled threads and the head of the bolt. As @redneck2 said, the force being applied to the bolt actually causes the bolt to elongate. It's the fact that this is an elastic deformation of the bolt material which causes the compression felt by the bolted up components. This elastic deformation ONLY occurs if the bolt actually turns while the torquing force is being applied...because it's the force of the threads pulling against the bolt head through the shaft of the bolt which causes this elongation. No turnie-turnie, no stretching.

Applying a lubricant will allow the bolt to turn easier than on dry threads...therefore it's easier to get that elongation for a given torque.

As I said earlier, the wet/dry torque requirements are typically specified in engineering drawings. But not everything we deal with has, or requires, that level of engineering specificity.

BUT...reducing a torque value by a given amount without understanding the engineering requirements behind it is not good. Every lubricant is different, which means the amount you may be able to reduce the torque value by will vary. And going by "some guy heard you should reduce the torque value by (X-amount) when you apply lubrication" may be a recipe for disaster when the components later catastrophically disassemble themselves under load.

SO...which is better? Wet torque or dry torque?

The answer is "THEY'RE QUALITATIVELY THE SAME"...with the caveat being "IF YOU FOLLOW THE ENGINEERING SPECIFICATIONS". If the engineering specification includes both a wet torque and a dry torque, either will provide the SAME bolt up tension if you apply them correctly.

If the engineering specification is "dry torque", then apply the specified dry torque.

If the engineering specificaiton is "wet torque", than apply the correct lubricant per the specified method and then apply the specified wet torque.

Here's an excerpt for nuclear mechanical joing make-up instructions from one of the shipyard procedures where I work:

"If no specific torque value is given in applicable technical manuals and no guidance is profided for fastener lubrication, the fasteners are to be lubricated with graphite in isopropanol per MIL-L-24131. This is not to be confused with when a torque IS given, but no lubricant is specified. In that case, teh fasteners are to be torqued dry (see paragraph 3.2.9.2.5.3)."

"Per Submarine Overhaul Specification (reference 2.1) and Surface Ship Overhaul Specification (Reference 2.2), Sections 9090-3-b and 9090-3-j; 'Where class drawings specify torque values for fasteners without reference to the application of a lubricant on the threads, the intent is to torque the fasteners in a "dry" (non-lubricated) condition.'"

In the world I work in, these things DO make a difference. And we don't arbitrarily apply a lubricant and reduce torque values because of it without written authorization because of this.

In the world of mounting a scope onto a rifle, the same rules in general apply: if a torque is given with no lubricant specified, then torque it without lubricant. However, in THIS world, you are not likely to cause any direct physical damage by choosing to apply a lubricant and either applying the same torque OR reducing the torque to some lower value.

Rebuilding a 350 four-bolt main? Probably ought to know these details.
 
Status
Not open for further replies.
Back
Top