Torque Confusion

[Traveler 45C]

Correct me if I’m wrong.

It is improper to torque a greased bolt to full specs if those specs call for a dry install, right? Something about the lube causing the bolt to actually be over torqued? Ok, so how much less does one torque a greased bolt if it’s spec’d for a dry install?

IOW’s, specs calls for 20ftlbs dry. Bolt gets greased to prevent corrosion and make getting it out easier (HE install, possibility of salt water intrusion). How much torque should be applied to that bolt? Is there some percentage or is this one of those ‘by feel’ standards?

I know we’ve been over this before. I can’t find the old posts.

 

[67hat34c]

Try to google wet torque, dry torque table.

 

[67hat34c]

ok i did some looking for you,

TYPICAL PERFORMANCE
An anti-seize lubricant used on a bolt helps to develop greater
clamp load for the same torque compared to an unlubricated
bolt. An additional benefit is greater uniformity in clamp load
among a series of bolts. The relationship between torque and
T = K x F x D
· T = Torque (in-lb, ft-lb, N-m)
· K = Torque coefficient or nut factor
· F = Clamp Load (lb, N)
· D = Nominal diameter of bolt (in, ft, m), determined
experimentally.

K Factor:
K factors are obtained on Grade 8, 1/2” steel bolts and Grade 5
nuts by a test procedure which measures torque tension
properties. Lubricant was applied to the bolt threads and both
faces of the washer. See properties chart for the torque
coefficient or K value for the anti-seize compounds. We feel
that this data fairly represents performance to be expected.
However, the manufacturer makes no warranty of specific performance
on any individual fastener. In critical applications, it is
necessary to determine K values independently.
Properties Typical Value
Torque coefficient, k on steel nuts and bolts .15
Type 304 stainless steel .16
Torque coefficient, k (solvent cleaned, not

 

[Traveler 45C]

Try to google wet torque, dry torque table.

That is so COOL!!! Thanks!

Now I can study up on how to build floating modular bridges for Army Tanks to use… I can’t wait to look through all of these pubs!

 

[Traveler 45C]

T = K x F x D
· T = Torque (in-lb, ft-lb, N-m)
· K = Torque coefficient or nut factor
· F = Clamp Load (lb, N)
· D = Nominal diameter of bolt (in, ft, m), determined
experimentally.

Ah! That explains it, thanks!
Cool stuff!

 

[spartonboat1]

GM stipulated that head bolt threads on Olds V8's were to to be "dipped" in motor oils before inserting and torquing, so lubricated threads are not unheard of, see the above posts.

 

[egaito]

OK, are we geeky or what?

I love this bar...I mean place....

 

[Traveler 45C]

OK, are we geeky or what?

Perhaps...

The torque tables are cool but they apply to the bolt, not the material/application that they are used in.
For my water pump install, DD specs are for the studs to be tightened to 20ft lbs and I'm assuming dry. How much torque should be applied if they go in wet?

 

[luckydave215]

Here's a useless tidbit for you.
The highest quality bolted assemblies (racing engine rod bolts or spacecraft structural hardware for example) aren't torqued in the first place. They're tightened until a cetrtain amount of "stretch" is measured with a micrometer.
The whole idea of bolted assemblies in the first place is to have a known amount of preload.
Torque is the easiest way to measure the preload in most cases, but when it really matters........

 

[Trojan]

Torque coefficient of a unknown lube and structural fastener is unmeasurable. The only way to come close is with a load cell and a multi series of test using the same material and fasteners for breakage and thread stripping. The formula does not mean Jack. You can get close on the torque using the Mike and stretch method. The stretch method is the best, but on bolts in blind holes it won't work. Lubed applications are a bear. There are too many variations. Lubed head bolts are one of the few applications, But these are special bolts. Torque is only a means to measure the clamping force of a joint. If you must tighten a lubed bolt be extra careful. Water is not a lube.



BILL

 

[spartonboat1]

OK, since this can of worms has been opened, there are a whole range of issues, some already addressed, related to this issue. If I did not know for a fact that lubed or in some other manner, treated threads were stipulated, I would utilize threaded fasteners that were as clean and dry as possible on both the bolt and the threaded base material. Also, if the thread quality is in doubt, "chase" the threads with tap/die so they are not rough and have a good profile.

Remember that the load is carried by the cross sectional area of the interface between the two mating threads, so factors include the overall length of the threaded interface, quality of threads, threads/length, i.e. fine or course threads, plus the threaded "materials", be they aluminum, brass, ferreous, etc. Then there are the many grades of bolts, etc.

My old British MG sports car ("Morris Garage", don't you know") had brass hold My down bolts for some engine parts, so when I overtorqued them, which I did, then they would strip out, not the more important bolts in the engine. Also, the various automakers specify an oilpan bolt that is "softer" than the pan. Overtorque? pan survives. Why do I know? Because a dealer replaced my pan bolt with a "steel" bolt, then proceeed to overtorque that bolt, stripping out the pan...yeesh.

Quick note on a patented thread profile at one time manufactured by the defunct Cheboygan Tap & Tool, Cheboygan, MI, that was slightly "off" vs. the ideal profile. As the nut/bolt was run in or down, a slight interference fit occurred that acted as a "locker" effect. This eliminated the need for other forms of locking materials or techniques. Don't know why did not take hold in the market.

yada, yada...

 

[bateau beau]

Ive always been told to "Tighten it up until it strips- then back it off half a turn... .

 

[Maynard Rupp]

In marine applications I always use an anti-sieze coating on threads. That is not really a grease or lube. I just use the torque values as published. You don't want to break the bolt, have it come loose, or distort the parts you are bolting together. You also surely need to be able to get the stuff apart later. Common sense, not formulas needs to be the rule here.

 

[Trojan]

The torque for a bolt/nut for a given application is derived by the amount of compression that is needed in the joint. Most bolts whether grade 5,8 or special all have 2 standard torques and compression ranges for the bolt or nut. One for a hard joint make up and one for a soft joint. Bolt grade is usually selected by its shear quality or the need to hold in a high compression situation. Adding oil increases the joint compression and the threads are usually 3 times the bolt diameter and are a grade 8. The torque is usually always lower then what the bolt size calls for. The oil prevents thread gaulding in a high compression joint. One of the hardest joint compression and torque applications to control is the U-bolt nut on a leaf spring and axle assembly. This is an extremely soft joint. Grade 5 is usually used in an application where the bolt size is greater than the compression needed. This lessons the torque and increases the shear of the bolt. Where compression is not the holding requirement a lock washer is used and it's compression will hold the bolt from coming loose. Making a bolt hold tight is not just cranking on the bolt or nut until it won't turn any more. Its trial and error testing with a torque wrench, a load cell and little thought. In some cases a real pitb. Proper torque is not as simple as people think.
BILL

 

[Nonchalant1]

Perhaps...

The torque tables are cool but they apply to the bolt, not the material/application that they are used in.
For my water pump install, DD specs are for the studs to be tightened to 20ft lbs and I'm assuming dry. How much torque should be applied if they go in wet?

I think DD specs are for oil dipped bolts.

Doug

 

[Traveler 45C]

Doug, I didn’t see that anywhere in the DD manual. I’ve got the ’85 version (I think, I’ll have to check) with all the changes, hard copy. What section is it in?

 

[Trojan]

I don't think DD has a wet torque. Head bolts are usually the ones. There aren't many applications for a wet torque. All most all bolts have a small amount oil an them. I know of no application where you must remove all oil from the threads. But that does not mean there aren't.

BILL

 

[yachtsmanbill]

I rebuilt an old pump with a 3-53 and DD wanted the headbolts coated with permatex liquid. Its mandatory that all the bolts be wire wheeled clean, washed in solvent and the holes tapped and washed and blown clean as well. Your only doing a half fast job if you dont anti seize the stuff. Why do you think they call it dope? Anti seize ESPECIALLY if the parts are aluminum with steel bolts. At that point you may want to run a drill through the alum to clean the corrosion crap outa the hole that the last jerk put together without anti seize. ws