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Old 09-06-2011, 09:04 PM   #361
DNF
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True or false.

"When using loctite or 'oil' on threads, reduce torque by 25%."

Just read that statement and have to say I have never heard it before.
Was in an article on installing a scope on your rifle.
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Old 09-07-2011, 01:18 AM   #362
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True.

Torque values are given for dry threads, or as otherwise stated. If you lubricate the threads, you reduce friction so have to reduce the dry torque value to get to the same tension on the fastener.
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Old 09-07-2011, 01:34 AM   #363
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Quote:
Originally Posted by DNF View Post
True or false.

"When using loctite or 'oil' on threads, reduce torque by 25%."

Just read that statement and have to say I have never heard it before.
Was in an article on installing a scope on your rifle.
Not so simple. The friction of the "underhead" contact area can be higher than that of the threads, and Loctite usually isn't applied there.
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Old 09-07-2011, 04:53 AM   #364
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Quote:
Originally Posted by DNF View Post
True or false.

"When using loctite or 'oil' on threads, reduce torque by 25%."

Just read that statement and have to say I have never heard it before.
Was in an article on installing a scope on your rifle.
Then since it's not a life or death situation for a human, take a suggestion from the words from a workbench expert out of a magazine for mounting that scope you don't know from Adam.

We do know that a considerable amount of friction must be overcome from thread friction as well as under-bolt head friction.

In one of the training manuals I just looked through I see that approximately 85 to 90% of the effort used to tighten a fastener is lost to friction and only 10 to 15% of that effort is used to generate clamp load.

More monkey wrenches to ponder. Cad plated, zinc plated, stainless, black iron, inconel, aluminum, titaneum, the age and condition of the tools used to cut the threads all offer differences of lubricity which can affect clamp load.

The true or false question you pose is sort of like asking which Stones song is best. Not a right or wrong answer in my opinion, but I can tell you that if you blindly reduce torque in applications on your bike really bad things will likely happen-and I hope blood and/or catastrophic failures never enter your world.

Don't forget that when we torque bolts, we're stretching them a determined amount to induce a clamp load between two parts sufficient enough to keep them from sliding back and forth on each other.

Now, just imagine what insufficient torque is going to allow happen....all over your bike....all inside of your engine.

Dirty
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Old 09-07-2011, 08:50 PM   #365
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Like I said I had never heard this before. Interesting answers.

News to me as they say.
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Old 09-07-2011, 09:31 PM   #366
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Originally Posted by DNF View Post
Like I said I had never heard this before. Interesting answers.

News to me as they say.
Find a bolting book by Bickford and read it.
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Old 09-08-2011, 07:23 AM   #367
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Find a bolting book by Bickford and read it.
Bene-what does it say? I'm curious to know. It's a legitimate question that has been posed on the site before and sparks slightly less debate than the oil thread or the which carry gun thread. The question stumped the band somewhat. But I still wouldn't go willy nillly reducing torque by 25% on lubed threads if the book calls for torquing fasteners with dry threads.

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Old 09-08-2011, 08:18 AM   #368
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Quote:
Originally Posted by dirty_sanchez View Post
Bene-what does it say? I'm curious to know. It's a legitimate question that has been posed on the site before and sparks slightly less debate than the oil thread or the which carry gun thread. The question stumped the band somewhat. But I still wouldn't go willy nillly reducing torque by 25% on lubed threads if the book calls for torquing fasteners with dry threads. Dirty
It basically says what you and I have been preaching, but takes things much further. John Bickford has little use for torque in critical applications because of the usual high friction-caused errors.

On a different note, an interesting goodie is how ASTM A-325 structural steel bolts are tightened. Such bolts are medium strength, and are not intended for reuse. Ironworkers needed something simple to assure that beam connections were good and tight, so engineers took a good look at how rivets work. Install a red hot rivet, hammer it real hard, and as it cools in contracts, pulling the beams even tighter and permanently stretching itself. The rivet ended up stretched past its room temp. yield strength (I never use the incorrect yield point).

OK, it that worked so well for rivets, why not bolts. Good, tighten them past yield. How? By using the "turn of the nut" method. This only works on solid metal-to-metal connections with no gap in between.

What does a mechanic do with bolts that are reused, and has no way to measure actual bolt stretch (elastic stretch, not permanent plastic stretch)? He has to rely on torque, using the usual dry friction factor (FF) of 0.2 for dry threads as a starting point. I have seen numbers as low as 0.11 when using lubes with high moly disulfide content, which should result in a huge ~45% torque reduction. I don't remember for certain, but I assume that both threads and head underside were lubed.

I think I'd reduce torques by ~25% only when using a high moly grease, and ~15% when using other greases, oils and Loctite, making sure to apply it to both areas. I'm in favor of slightly overtightening critical bolts rather than under.
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Old 09-08-2011, 09:02 AM   #369
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Loctite paste

An inmate helped me out with changing my rear shock out on my KLR and when I was putting some bolts back in, he had this loctite paste stuff versus the liquid type and I am wondering if anyone has heard of this? I check several auto parts stores, but nothing, only liquid.
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Old 09-08-2011, 09:17 AM   #370
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Time for the story I referred to in msg. #334.

While working at a large nuke power plant, a maintenance guy handed be a good size nut. I had some of them well enough trained to hand deliver small broken stuff to my office. This nut was a 2 1/4" one, meaning the flat-to-flat size was 3 1/2".

What made this interesting was that the nut had a broken stud inside it, filling the hole but not extending beyond either face. One glance at the fracture surface told me it was a typical fatigue fracture, caused by stresses/loads that were in excess of the stud's preload. Not good so far.

It was the other end/face of the nut where the surprise was. I discovered that someone had cut the free end of the stud off flush with the nut, and then welded a nice bead all the way around the stud/nut interface. WTF?

Seems that several of these nuts had loosened and fallen from one grated floor to the lower one, ~20'. They were used on a main steam pipe hanger, where the nut temp. was ~400+ F, too hot for long term Loctite use. What to do?

Without informing engineering (me in particular), maint. decided to use "real high temp. Loctite", aka welding. Being just bright enough not to weld on the stressed side of the stud, they "did the deed". I mean, "what's the worst that could happen", right?

Unfortunately they didn't know that bolting fatigue failures are usually caused by loss of/insufficient preload, which of course they failed to correct. So, instead of a 4 lb. nut falling 20' where it could hit someone, they added another lb. or so. The nut I received was actually the 2nd time their welded nut fell down. Seems they must have though it was just a freak event. Right.

The fix? Tighten the nuts (every one of hundreds) right to the min. yield strength of the studs at temp., and let me know before you try any other half-assed lookie-boy stuff.
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Old 09-08-2011, 12:21 PM   #371
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Quote:
Originally Posted by Benesesso View Post
It basically says what you and I have been preaching, but takes things much further. John Bickford has little use for torque in critical applications because of the usual high friction-caused errors.

On a different note, an interesting goodie is how ASTM A-325 structural steel bolts are tightened. Such bolts are medium strength, and are not intended for reuse. Ironworkers needed something simple to assure that beam connections were good and tight, so engineers took a good look at how rivets work. Install a red hot rivet, hammer it real hard, and as it cools in contracts, pulling the beams even tighter and permanently stretching itself. The rivet ended up stretched past its room temp. yield strength (I never use the incorrect yield point).

OK, it that worked so well for rivets, why not bolts. Good, tighten them past yield. How? By using the "turn of the nut" method. This only works on solid metal-to-metal connections with no gap in between.

What does a mechanic do with bolts that are reused, and has no way to measure actual bolt stretch (elastic stretch, not permanent plastic stretch)? He has to rely on torque, using the usual dry friction factor (FF) of 0.2 for dry threads as a starting point. I have seen numbers as low as 0.11 when using lubes with high moly disulfide content, which should result in a huge ~45% torque reduction. I don't remember for certain, but I assume that both threads and head underside were lubed.

I think I'd reduce torques by ~25% only when using a high moly grease, and ~15% when using other greases, oils and Loctite, making sure to apply it to both areas. I'm in favor of slightly overtightening critical bolts rather than under.
Amazon has your Bickford book. For $173.00...........
http://www.amazon.com/Introduction-D...5504314&sr=1-1

Here is a less expensive one that is a decent practical guide. It's by Carroll Smith, who is an engineer and was also Carroll Shelby's crew chief.
http://www.amazon.com/Fasteners-Plum...5504842&sr=1-1

Another by the same author that covers race prep and design in a practical sense.
http://www.amazon.com/Engineer-Motor...5505104&sr=1-1

The auto industry has been using torque to yield fasteners for awhile, notably for head bolts. They say to tighten to a specified torque value and then rotate X number of degrees. The fasteners are single use only, and must be replaced each time they are removed.

If you buy a set of competition conrods from Carrillo, they come with the proper lubricant for the bolts, and also detailed instructions on lubrication and torquing of the rod bilts. They are 12 point SPS NAS series 180,000 psi rated.
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Old 09-08-2011, 04:54 PM   #372
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Quote:
Originally Posted by Asatrur View Post
An inmate helped me out with changing my rear shock out on my KLR and when I was putting some bolts back in, he had this loctite paste stuff versus the liquid type and I am wondering if anyone has heard of this? I check several auto parts stores, but nothing, only liquid.
Thanks,
Asatrur
My favorite:
http://www.amazon.com/Loctite-QuickS.../dp/B000132VH6
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Old 09-09-2011, 04:58 PM   #373
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My damn speedometer cable just will not stay attached to the speedometer no matter how much I tighten it--it always jiggles loose within 500 miles or so. What do I use?
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Old 09-09-2011, 05:20 PM   #374
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My damn speedometer cable just will not stay attached to the speedometer no matter how much I tighten it--it always jiggles loose within 500 miles or so. What do I use?
Epoxy. Make sure it's dry.
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Old 09-09-2011, 07:54 PM   #375
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Epoxy. Make sure it's dry.
Or a blue medium strength threadlocker or low strength purple.....so long as it's metal male threads going into metal female threads.

Don't forget threadlockers will stress crack many types of plastics faster than you can scratch your nut sack.

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