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Chris Miller
Frequent User
Username: cjm51213

Post Number: 56
Registered: 5-2013
Posted on Saturday, 17 May, 2014 - 01:37 pm:   Edit PostDelete PostView Post/Check IP

Hi Folks,

As I prepare for re-assembly, I want to leave things better than I found them, since I expect that I will be here again. Some of these parts were really stubborn, so my first thought was anti-seize. And my second thought was thread locker.

And my third thought was, maybe these are the same thing. It seems like they might be at cross-purposes, but a thread locker might also be a competent anti-seize compound.

I think Permatex Silver looks fine, but I am totally guessing.

Discuss and recommend.

Thanks for the help,

Chris.
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 3019
Registered: 4-2003
Posted on Saturday, 17 May, 2014 - 06:12 pm:   Edit PostDelete PostView Post/Check IP

Nickel antiseize is best. Be sure to reduce the torque on tightening to suit as the lubricant causes a higher bolt/stud tension for any given torque. With a new crush washer it is sufficient to take up the crush and torque to 2/3 the standard spec.

RT.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 800
Registered: 6-2009
Posted on Sunday, 18 May, 2014 - 01:23 am:   Edit PostDelete PostView Post/Check IP

I second the nickel anti-seize. The silver-colored stuff from Permatex is their nickel anti-seize lubricant. I've had a tiny tube of the stuff going for years since you don't use much.

When putting the accumulators and accumulator control valves together about the only pieces that you can use a torque wrench with are the end plug of the ACV and the adapter/crush washer that mate with the ACV body.

For the ring on the accumulator sphere you're still going to want it to be as tight as you can get it using your own body weight on the wrench.

I used anti-seize on the accumulator ring, accumulator port threads on the top and bottom, the adapter threads top and bottom, and even on the line nut threads for the various hydraulic lines. If you apply carefully it makes it so much easier for the next person who has to take these things apart again and none of these threaded surfaces have RR363 flow going over them.

Just a dab'll do ya! (Those of us "of a certain age" will get the original reference, but it still applies here).

Brian
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 399
Registered: 5-2012
Posted on Sunday, 18 May, 2014 - 05:50 am:   Edit PostDelete PostView Post/Check IP

Chris

I also recommend using anti-seize, however make sure it doesn't come into contact with any rubber parts. Take particular attention when applying it to the accumulator collar; you really do not want it coming into contact with the diaphragm.

Geoff
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Bob uk
Unregistered guest
Posted From: 94.197.122.82
Posted on Sunday, 18 May, 2014 - 06:43 am:   Edit PostDelete PostView Post/Check IP

I find copper grease ok for general stuff on suspension etc
Chassis grease also works ok

Any place where dot is I use Comma dot compatible red grease

In 1989 I greased my nuts and they are still oily 25 years later

Wheel nuts

(Message approved by david_gore)
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 61
Registered: 5-2013
Posted on Tuesday, 20 May, 2014 - 04:40 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

My original question was not well written.

Anti-seize increases the likelihood that an attachment may vibrate loose. Thead-locker increases the likelihood that you may not be able to get it off the next time you want to...

It needs to stay on until I want it off, and then it needs to come off!

Since thread-locker coats the threads, it has "anti-seize" characteristics, or at least it offers some protection against corrosion and oxidation. Additionally, some tread-lockers are designed for bolts that may have to be removed, and some are designed to make removal very difficult. For example, Permatex blue is apparently low enough strength that it requires no special consideration for later removal, but Permatex red is quite stubborn and requires heat to release it.

Some systems give clues. For example, on hydraulic nipples and fittings, I think anti-seize alone is a good choice, since anything that works itself loose will cause a drip that is easy to discover and repair. There are probably other examples.

For attachments, where things may loosen and fall off before discovery, I want to use thread locker, but not if I am making an irrevocable decision.

So, with this clarification, my question is, can I use, Permatex blue as anti-sieze to prevent vibration loosening in those cases where there would not be other clues, or should I simply stick with anti-seize, and proper torque specs.? (And now that I've said it, where do I find torque specs?)

Thanks for the help,

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 812
Registered: 6-2009
Posted on Tuesday, 20 May, 2014 - 04:59 am:   Edit PostDelete PostView Post/Check IP

The Torque Specs for everything on these cars is in Chapter P - Torque Tightening Figures, of the workshop manual.

I simply don't feel like going into it again, but there's a lot of formal literature out there now about the ineffectiveness of things like lock washers and that an adequately (for the purpose and environment) torqued connection should hold without any additional "fixing" methods needed.

Anti-seize lubricants actually make it easier to get the same amount of "stretch" in your connectors with less than the specified torque. Richard Treacy noted this several posts back.

I never use anything that will make getting a threaded fastener apart in the future more difficult. Anti-seize shouldn't make it any more likely that a connection will come apart unless it was inadequately torqued in the first place.

Brian
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 63
Registered: 5-2013
Posted on Tuesday, 20 May, 2014 - 05:05 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,

> I never use anything that will make getting a threaded fastener
> apart in the future more difficult. Anti-seize shouldn't make it
> any more likely that a connection will come apart unless it was
> inadequately torqued in the first place.

I hear you telling me, "Don't use thread-locker; it will cause more problems than it solves.". This completely addresses my fears and answers my question.

Thanks very much.

Chris.
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 65
Registered: 5-2013
Posted on Wednesday, 21 May, 2014 - 12:39 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

I have inadvertently discovered this, and its not clear what I should do. Richard recommends that I use 2/3 the torque spec when I also use anti-seize lubricant on the threads, and that just sounds right. Lubrication reduces the friction, which will increase the clamping pressure, or "stretch", for a given torque spec. Richard uses "Nickle" and I have "Silver", so I called Permatex to get more details on that "2/3" figure. Does it vary across "Silver", "Copper" and "Nickle"? How is "2/3" calculated and what is the tolerance?

I was shocked. Permatex says the number is not 2/3, it is 1! I was on the phone with them for a long time. I explained that my application was automotive, and it was a classic car, meaning the hardware has been in use for many years and I asked them why the lubrication of the anti-seize compound had no effect on the torque spec. They couldn't tell me, but the did give it to me in writing:

http://www.permatex.com/documents/TDS/automotive/80078.pdf




Excerpted from above:

DIRECTIONS FOR USE
1. Clean mating surfaces before application
2. For best results, apply to clean, dry surfaces.
3. Clean surfaces with Permatex Brake & Parts Cleaner.
4. Wire brush any loose surface rust.
5. Apply Anti Seize to the parts that require protection.
6. Reassemble parts using *normal* torque values.
7. Wipe off excess material.
8. Clean brush on aerosol product to make future applications easier.

Well, now I'm not sure what I should do. I am loath to ignore the experience and advice from Richard, but I am equally compelled to follow manufacturer product recommendations. So, what? I split the difference and use 5/6? (-:

What should I do?

Thanks for the help,

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 816
Registered: 6-2009
Posted on Wednesday, 21 May, 2014 - 01:29 am:   Edit PostDelete PostView Post/Check IP

Chris,

First, just for the historical record, it appears that Permatex makes at least three different anti-seize lubricants and here are links to the technical data sheets:

Copper
Nickel
"Generic" - Aluminum, Copper, Graphite [silver color]

Their broad statements about applications:

Copper
Permatex Copper Anti-Seize was designed specifically for use on stainless steel or similar alloys. It protects threaded fasteners and fittings from heat, freezing, seizure or galling at temperatures from -30°F to 1800°F. It may be used on pumps, sensors, valves, nuts and bolts where extreme conditions of heat exist. Permatex Copper Anti-Seize also provides good electrical conductivity.
TYPICAL APPLICATIONS
• Spark plug threads installed into aluminum heads
• Exhaust manifold and engine bolts
• Oxygen sensors
• Knock sensors
• Thermostat housing bolts
• Fuel filter fittings
• Battery cable connections

Nickel
Permatex Nickel Anti-Seize was designed specifically for use on stainless steel or similar alloys. It protects threaded fasteners and fittings from heat, freezing, seizure or galling at temperatures from -65°F to 2400°F. It may be used on pumps, sensors, valves, nuts and bolts where extreme conditions of heat exist.
TYPICAL APPLICATIONS
• Exhaust manifold bolts
• Exhaust system bolts
• Muffler clamps
• Tailpipe assemblies
• Catalytic converter assemblies

"Generic"
• Effectively lubricates assemblies exposed to high temperatures and heavy contact pressures
• Suitable for service up to 870°C (1,600°F)
• Reduce corrosion and seizing due to weathering or chemicals
• Permits easy disassembly of parts exposed to heat or corrosive environments
• Brush-top aerosol available
TYPICAL APPLICATIONS
• Spark plug threads
• Exhaust manifold and engine bolts
• Anchor pins on brake assemblies
• U-bolts and spring bolts
• Lubricates and permits easy disassembly of assemblies exposed to high temperatures and heavy contact pressures, such as boiler and oven parts, jet engines, and industrial turbines.
• Hinges, gears, chain, sprockets and rollers

You have the "generic" which I'd not known about before now. Any of the above would appear to be fine for putting the accumulator back together and all are applied sparingly.

The reasons for reducing torque when using anti-seize have been thoroughly discussed here, I believe, and all over the place on the web. Richard is not the only one who reduces the amount of torque.

The anti-seize manufacturers would be putting themselves in a potential legal tight spot were they to ever recommend deviating from a product manufacturer's torque specifications so they'll never do that.

In the end, do what you feel comfortable with here. For the "big threaded" areas you can't use a torque wrench anyway and the threads are robust. I used the specified torque for the ACV end cap and adapter. I made the accumulator sphere ring as tight as I could possibly get it using the wrench and my body. The ACV to sphere was hand tightened then given a gentle tap or two with a hammer to nip it up a bit tighter.

Any of the connections you can tweak if they leak after the system is pressurized should be minimally tight to begin with - just stopped with a tiny bit of additional turn with the wrench. You can always give a bit more tightening if needed.

Brian
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 817
Registered: 6-2009
Posted on Wednesday, 21 May, 2014 - 05:08 am:   Edit PostDelete PostView Post/Check IP

Chris,

I thought I had might as well go out and see if I could find what I thought were either well-supported or "pretty much definitive" references on changing torque when using anti-seize lubricant if the original torque figures presumed that no lubricant was being used. Here's what I found:

Definitive for this line of Bostik products:
NeverSeez Brochure
see also the technical data sheets for the various NeverSeez products.

From Anti-Seize Technologies, a maker of anti-seize lubricant on the need to reduce torque when using anti-seize lubricant.

Reducing Torque on mechanicsupport.com
Torque Wrench on mechanicsupport.com

While I don't agree with this guy's conclusion to "never use anti-seize on fasteners" his anecdotal experiments show that you need to reduce torque if you use them in most cases.

Thus, I retract my earlier statement about anti-seize manufacturers not recommending a change from product manufacturers torque specifications when it can be reasonably presumed that those specs were made using dry fasteners.

Brian
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 67
Registered: 5-2013
Posted on Wednesday, 21 May, 2014 - 05:38 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,


> Thus, I retract my earlier statement about anti-seize
> manufacturers not recommending a change from product
> manufacturers torque specifications when it can be
> reasonably presumed that those specs were made using
> dry fasteners.

Yeah... That is my quandary. Conventional wisdom and *my understanding of the problem* dictates that you would *have* to reduce the torque to below spec when you add a thread lubricant, because torque specs are always stated for dry fasteners, and lubrication will reduce the friction thereby increasing the clamping force.

So, now we have more confusion and disagreement: Conventional Wisdom and NeverSeez line up against Permatex. The guys at Permatex are not morons, so I can't understand their recommendation to use the original torque spec. There *must* be some unwritten understanding somewhere that I am missing, like they state somewhere else that the "original" torque specs are the "original" torque specs when you use a any thread lubricant, not necessarily Permatex. I'm going to contact them again to see if I can get a statement from engineering about why their product will not change the torque spec.

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 818
Registered: 6-2009
Posted on Wednesday, 21 May, 2014 - 05:49 am:   Edit PostDelete PostView Post/Check IP

Chris,

I doubt you will get a statement from engineering. This is one of the problems with our (read: United States) society having gone into super-litigious mode and turning to the courts whenever any moderate to major problem arises.

What Permatex has in their TDSs was certainly vetted by their product liability attorneys and there will likely be no statements, at least in writing, that contradict that by anyone in the company. They're also one of the few companies that are marketing their products to the general public rather than "to the trade."

Clearly, for the reasons specified in the documentation I supplied, your understanding of the problem is the correct one. Manufacturers who are supplying these products "to the trade" clearly indicate that torque reduction is mandatory if you don't want to risk breaking fasteners.

Some things are far less likely to reach the breaking point than others, but if you're able to use a torque wrench for a fastener I'd definitely reduce the torque within the ranges specified by the other manufacturers for the similar product in their line. These lubricants are "not rocket science" and are relatively similar within their classes.

Brian, who still thinks this is much ado about nothing since most of the things we're talking about are going to have to be tightened "by feel" anyway. In other situations, not so much.
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Bob uk
Unregistered guest
Posted From: 94.197.122.74
Posted on Wednesday, 21 May, 2014 - 07:28 am:   Edit PostDelete PostView Post/Check IP

Engineering common sense is required with this subject

Bits do not fall off rolls royce

Oily threads allow more of the torque applied to go into the clamping force

The torque figures given are fine to use

To break a bolt by over torqueing requires a lot more torque than the tables for that bolt

When the bolt is tightened it stretches

When the bolt is loosened it should return to its original length

If the bolt is over tightened then it will be stretched beyond its critical point at which point it's utensil strength rapidly deminishes and when released it will be stretched and not spring back to its original length

The bolt then continually comes loose until it breaks

On the bolt head are numbers say 8.8

This is the strength of the bolt

No numbers means ungraded bolt

Nuts are far stronger because the force is compressive and the threads strip first

Screw threads are like a wedge wrapped around a cylinder

The finer the wedge the more clamp you get

Torqueing bolts to the tables is the safest way

Once one has the feel gained from using a torque wrench then for general stuff hand feel is fine

(Message approved by david_gore)
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David Gore
Moderator
Username: david_gore

Post Number: 1384
Registered: 4-2003
Posted on Wednesday, 21 May, 2014 - 08:55 am:   Edit PostDelete PostView Post/Check IP

I have been following this discussion with great interest and my contribution is as follows:

It is my impression two points of view are represented in this discussion:

1. Using sufficient torque to prevent the fastener undoing in service.

2. Using sufficient torque to tension the fastener to a required preload to suit the application.

I am having some difficulty reconciling the reasoning behind lubricating the threads allowing the torque to be reduced as the essential stressing of the fastener to provide long-term retention is achieved by the elongation of the fastener induced by the engaged thread; the only effect of the lubrication is to reduce the friction during the tightening process making it easier and quicker to complete the fastening process.

My procedure for torquing fasteners has always been a 3 step operation:

1. initial torquing to 1/3 the specified torque to settle things down.

2. torquing to 2/3 the specified torque to achieve some elongation to fully engage the components being fastened.

3. torquing to the specified torque.

The only times I have encountered problems with fasteners becoming loose in service has been when I have taken short-cuts during the torquing process by deleting the intermediate torquing and not lubricating the threads. This resulted in friction-induced loads triggering the torque indicator before the fastener had been fully tensioned to the specified torque.

Contrary to some comments in previous posts, I would expect torque specifications to be based on lubricated threads and not dry threads due to the variations in actual stress induced in the fasteners by the variations in torque required to overcome the friction associated with dry threads. Lubricated threads are the only way that I can see for the required elongation in the fastener to be uniformly and consistently achieved in practice.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 819
Registered: 6-2009
Posted on Wednesday, 21 May, 2014 - 10:04 am:   Edit PostDelete PostView Post/Check IP

David,

Please go out and do some digging and you'll see that, with specific exceptions, virtually all torque tightening figures are noted as given for dry threads. It's noted again and again in many documents.

I actually would have expected this since, in practice, I've seldom seen fasteners routinely lubricated before connecting. There are, of course, specific applications where lubrication was routine, and I'd expect those figures to take that into account.

Your procedure sounds ideal. That being said, I've seldom seen that going on in the many garages I've frequented over the years. I always hope that what's generally done in practice is what's been considered when reading specs rather than what's done in an ideal situation.

Brian
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David Gore
Moderator
Username: david_gore

Post Number: 1386
Registered: 4-2003
Posted on Wednesday, 21 May, 2014 - 12:50 pm:   Edit PostDelete PostView Post/Check IP

Hi Brian,

We will have to agree to disagree in this instance as I will stand 100% behind my last paragraph.

The torque specification is based on the torque required to generate a stress in the fastener which is below the yield stress/proof stress for the grade of fastener being used. This stress is created by the "ramp effect" of the thread stretching the bolt shank the required amount to generate this internal stress to lock the components together.

To my simple mind, the following equation should apply:

Torque required to stress bolt + Torque required to overcome friction = Specified Torque

As the torque required to overcome friction is variable and the torque required to stress the bolt is constant and engineers are invariably conservative risk takers; I find it very hard to believe specifying engineers would accept a situation where variable friction loads could result in unpredictable lower or higher internal stresses. There is no easy way of determining the friction component due to the large number of variables contributing to the friction load such as relative dimensions of the male/female threads, engaged length of the thread, thread height, surface roughness, ambient temperature etc. Thread lubrication reduces the extent to which these variables can affect the induced stress to a level where reproducibility of the desired internal stress is within acceptable limits.

The observation in your last paragraph is correct however it must be seen in the context of Bob-UK's comment that experienced mechanics can tighten by feel rather than having to use a tension wrench. In my own case, I prefer to use the tension wrench for the added confidence that "I have got it right first time" and I lubricate all threads with oil or Nickel anti-seize grease depending on the working environment to be certain the fasteners function in the way the designer intended. I have endured enough instances of "acting in haste and repenting at leisure" from taking short-cuts that resulted in future problems.

I would be interested in knowing what procedures apply in the aviation industry as I expect the safety considerations involved would require "best practice" at all times.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 821
Registered: 6-2009
Posted on Wednesday, 21 May, 2014 - 01:31 pm:   Edit PostDelete PostView Post/Check IP

David,

I shall ask my friend, the airplane mechanic and instructor in aviation repair (developed the program, actually) at our local community college. He's been "in the biz" for decades, so he should know. I shall report back once I've heard from him.

Brian
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Bob uk
Unregistered guest
Posted From: 94.197.122.73
Posted on Thursday, 22 May, 2014 - 07:31 am:   Edit PostDelete PostView Post/Check IP

The torture figures I'm tables are for dry CLEAN threads

Oil does make a difference

Where the job is critical like say the fan on a jet engine then tis becomes important

Something like a cylinder head, then as long as the bolts are evenlying tortured and within say 5# of the correct figure, then the job a good'un

(Message approved by david_gore)
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 825
Registered: 6-2009
Posted on Thursday, 22 May, 2014 - 09:03 am:   Edit PostDelete PostView Post/Check IP

Direct from my friend the aviation maintenance instructor:

In my experience, and generally accepted, aviation torques are dry unless otherwise specified by the manufacturer. Modern aircraft maintenance manuals are written with a chapter called "Standard Practices" that addresses torques and other tasks. If the torque is lubricated, tightened then loosened, or whatever, it is usually spelled out in instructions specific to the individual event.

This is utterly consistent with the vast majority of documentation I've read. The General Information on Torque Specification sheet from AST Industries that I posted a link to earlier stated, "Values: Most torque values are based on non-lubricated fasteners." It wasn't the only reference making this statement, but I wasn't going for a flood of links.

Brian
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 826
Registered: 6-2009
Posted on Friday, 23 May, 2014 - 12:30 am:   Edit PostDelete PostView Post/Check IP

I also thought these bolt torque charts were very informative, too:

at repairengineering.com

at Portland Bolt & Manufacturing Company

at raskcycle.com

It was also interesting to read that the bolt head, and whether it's lubricated on its underside or not, plays an additional critical role in how much torque should be applied to get the desired clamping force. Several online articles/blogs make reference to this and all use the article on helicopter rotor drive plate bolt failure as a reference:

What Do Torque Wrenches Measure?

How Antiseize Changes Bolt Torque

See "Failure of bolts in helicopter main rotor drive plate assembly due to improper application of lubricant" by N. Eliaz, G. Gheorghiu, H. Sheinkopf, O. Levi, G. Shemesh, A. Mordecai, H. Artzi, Published in Engineering Failure Analysis #10, 443-451, www.sciencedirect.com

Brian
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 69
Registered: 5-2013
Posted on Friday, 23 May, 2014 - 01:07 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,

Really excellent exhibits.

I looked at RepairEngineering.com which has a lot in that chart. I picked "3/8"-16 as representative. If I'm reading this correctly, if looks like the torque spec with lubricant is 3/4 the "dry" spec., which lines up with the "2/3" factor that has been suggested.

Portland Bolt is apparently using "1/2", but their article, "Tension vs. Torque Explained" is informative. Here I see the formula that Permatex gave me "T=KDP/12". Portland Bolt's value for K is interesting. They use "0.20" for "untreated" and Permatex uses "0.18" for their anti-seize, which tells me that Permatex Anti-Seize is a marginal lubricant, so their "use original torque specifications" recommendation now sounds reasonable.

There is nothing, with the possible exception of a fire, or the whistle to quit work, that can break up a conversation as quickly as a guy who actually knows what he is talking about.

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 827
Registered: 6-2009
Posted on Friday, 23 May, 2014 - 01:36 am:   Edit PostDelete PostView Post/Check IP

Chris,

I also found it quite interesting, and utterly unsurprising, that this statement was made in the Results and discussion: Secondly, although the helicopter’s maintenance manual requires that the nuts be torque-wrenched while holding the bolts, it has become common in the field to wrench the bolts while holding the nuts (for convenience reasons).

This harks back to my previous comment, " I always hope that what's generally done in practice is what's been considered when reading specs rather than what's done in an ideal situation." I guess I really should have said, "when writing specs," or, "when formulating specs." I've almost never seen someone torque the nut and hold the bolt (when a nut and bolt are involved) but holding the nut and torquing the bolt is almost universal. Yes, you can write specs (and, clearly, it's done), that makes the opposite presumption but that's simply bad practice when you know that field practices are to do something routinely that you've chosen to ignore.

Although it's got nothing to do with torque, I've learned this lesson in both my tech support business and my time as a speech-language/cognitive therapist. If you don't come up with something that the client wants to use in light of how they actually go about their lives it is almost destined to fail. There are those occasions where you can teach something that causes "a lightbulb to go on" and changes practice because it actually makes things easier, but these are the exception rather than the rule. If you're "the outsider" then you better gain some knowledge of how "those on the inside" actually do things and work within those parameters whenever possible.

Brian
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Chris Miller
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Username: cjm51213

Post Number: 71
Registered: 5-2013
Posted on Friday, 23 May, 2014 - 03:51 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

My (excerpted) response from Permatex is:

"... The directions say “reassemble parts using normal torque values”. ... the procedure is to torque to the manufacturer’s recommended torque. The clamp load will increase, but not enough to cause any damage."

Chris.
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David Gore
Moderator
Username: david_gore

Post Number: 1387
Registered: 4-2003
Posted on Friday, 23 May, 2014 - 07:55 am:   Edit PostDelete PostView Post/Check IP

OK - I surrender but in a state of concern that engineers have accepted a practice that does not control a variable that in practice can significantly influence fastener clamping force.

It further concerns me that most torque tables do not include separate specifications for lubricated and non-lubricated fasteners which results in various "rules of thumb" which may not be accurate being used where ease of future disassembly after the initial repair/maintenance is an important consideration. The current practice serves to facilitate automated production line assembly but we all know the problems encountered when trying to remove these fasteners for maintenance purposes especially if they have not been touched since the original assembly process.

For Brian's comment about the workshop practice of using the bolt head instead of the nut when tightening a bolt and nut assembly; I suggest this is a result of the person being too lazy to get a long socket from their tool box for the nut to ensure the emergent bolt thread does not disengage the socket during torquing. It also reflects the changes in training practice over the years; 50 years ago I recall seeing apprentices being severely and publicly castigated by experienced tradesmen for not following specified procedures to train them for their future when they were qualified and responsible for their work; today such castigation would not be allowed as it would be seen as a form of workplace harassment. However, it did result in persons who took pride in their work and in doing it properly.
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Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1204
Registered: 6-2006
Posted on Friday, 23 May, 2014 - 06:04 pm:   Edit PostDelete PostView Post/Check IP

David I agree with the problems caused by modern teaching practice where how somebody feels is more important tha getting the facts driven home :-(

Regarding tightening bolts not nuts, How could anybody think that would work, especially in sutuations where situations where the bolt is binding or something is is hanging on the bolt. You wouldn't tighten the bolt with your fingers and hold the nut, you'd spin the nut on. Why? Because the torque needed is next to zero.

Torque measurements tend to be a measure of fixing tension before it stretches to a deformed state.

Newer fixings to things like cylinder heads do stretch the bolts to beyond that point. This means torquing down to remove any gap, then rotating the fixing through a set angle (usually in steps as you would with a torque wrench) and this angle stretches the fixing by a set distance determined by the angle turnes x the thread pitch.

I love the way the RR manuals instruct you to tighten down straight 6 and earlier head gasket fixings. As tight as you can with a 6" spanner ..... no matter if your 5, 25, or 95. :-)

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