Torque

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FionaZuppa said:
[copy paste as the timer ran dry on that last post]
and just to note, i did not argue that a torque spec is not the right spec for the given fastener/application. i did mention as a Q if the torque specs shown on a ocpd paper accounts for dry or not, etc. in other words, the paper says 20in-lb which relates to perhaps real 18in-lb in tension, etc. in other words, lubrication will always make real torque (tension) match the tool setting better, etc. how the spec is derived and written to paper is something completely different.

and yes, N∙m is not the same as m∙N

i think most will live with ft-lb when it comes to torque and not really worry about the work part ;)
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For most of us here our concern is electrical connections - I have yet to see mechanical lug that has instructions to lubricate the thing before tightening, I would assume their tightening torque recommendations are to tighten it as is with no additional lubricating.
 
171014-2109 EDT

FionaZuppa:

kwired's comment is correct for electrical connections. My expectation is that somewhere theory, practical needs, and extensive experiments resulted in the specifications for torque.

To lubricate a thread, and, then use a torque specification for that thread that is based on an as is thread (meaning how the spec was developed) is likely to cause unwanted results.

The video you linked to is interesting. I am not sure how the experiments were run and therefore how I would use the displayed data. The conclusion I drew from the video was that this company has developed a thread lubricant that can provide a small random variation in the prediction of bolt (stud) tension relative to applied torque.

For applications requiring accurate control of bolt tension this capability is important. But the torque specifications to be used must be based on tests performed on threads with this lubricant applied.

.
 
kwired said:
For most of us here our concern is electrical connections - I have yet to see mechanical lug that has instructions to lubricate the thing before tightening, I would assume their tightening torque recommendations are to tighten it as is with no additional lubricating.
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Aluminum lugs/screws are often gonna get NoAlOx all over them. Not a lubricant?
 
gar said:
171014-2109 EDT

FionaZuppa:

kwired's comment is correct for electrical connections. My expectation is that somewhere theory, practical needs, and extensive experiments resulted in the specifications for torque.

To lubricate a thread, and, then use a torque specification for that thread that is based on an as is thread (meaning how the spec was developed) is likely to cause unwanted results.

The video you linked to is interesting. I am not sure how the experiments were run and therefore how I would use the displayed data. The conclusion I drew from the video was that this company has developed a thread lubricant that can provide a small random variation in the prediction of bolt (stud) tension relative to applied torque.

For applications requiring accurate control of bolt tension this capability is important. But the torque specifications to be used must be based on tests performed on threads with this lubricant applied.

.
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I would add that the people who did the testing and made the video are trying to make money selling thread lubricant. Makes me suspicious.
 
kwired said:
Does instructions say to coat the screw threads of the mechanical connector or to just coat the aluminum conductor being terminated?
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I'm merely acknowledging that it is quite common that the threads get some during the process, especially in a difficult bend/insertion situation. It takes a tiny amount on just a couple threads to maybe make a difference, IF this difference is worth worrying about, as some say.

Perhaps I shouldn't have said "all over them," but that does remind me that there have been several times, I've completely removed the screw from the lug to make it easier to get the conductor into it, and the threads definitely got plenty in the process. Never thought about that at the time.
 
GoldDigger said:
"The recipe for perfect toast
Is easy to express.
Toast it till it burns, and then
Twenty seconds less."
---Piet Hein​
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hah, i thought it was

"The recipe for perfect toast
Is easy to express.
Toast it till it burns, and then
scrape off with a butter knife."
 
You'll need 3/8" and 1/4", because larger lugs are outside the usable range of 1/4".

Pay attention to the difference between in vs ft; lbs vs oz
 
GoldDigger said:
When I do that I end up with lots of burnt crumbs in the next portion of butter. :slaphead:
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ah, your method is off. its scrape scrape scrape all the slices with a dry knife 1st (because there is no time to rethink the timer), then go back for big swath of butter, applying just enough to each slice quickly, so that when you get to the end of the slice stack all the butter on knife is gone, this way you are only in the tub once ;)

somehow i have learned that efficiency method, and nobody complains that the butter tub is full of burnt bread crumbs. :blink:

ok, this thread has been beaten to death a few times.
cheers.

 
ActionDave said:
I was taught you tighten until you are one quarter turn away from stripping the threads and then back off an eighth.
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Okay, let's switch to a different horse.

Assuming you have learned exactly what point of the turn would strip the threads before doing so, why stop at 1/4 away and then back off 1/8? Why wouldn't you just stop at 3/8 away?

Taking that concept to even measured torques, what happens if you over-torque and then take some off? Have you squished the conductor to the higher value and have less connection now? Negligible?
 
And then you have some of the torquing specifications for engines like Caterpillar. Torque to a certain value, then tighten the bolt an additional amount of degrees!
 
But back to the original subject, the only torque wrenches I have are the 3/8" and 1/2" craftsman ones I bought 45 years or so ago.

and yeah I pretty much already know how much to pull on a wrench to snap the bolt off.

So, what are other people using and what seems to be practical to use for obtaining the proper torque on fasteners?
 
FionaZuppa said:
in automotive, about 50% of the nuts/bolts on the vehicle have some sort of thread locker on them, which also serves as lubrication when tightening to spec.

so although i dont disagree with you, i would say "it depends".

and i didnt say you dont get accurate torq if its dry, but its way more complex to do accurately because so many other factors are involved. perhaps in the lower in-lbs range the dry friction makes no big diff, or they added a few in-lb to the spec?

and to lubricate i might choose a dry spray perhaps, or a thread lock paste or liquid, but typically not an oil.
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And, in the auto trade, lug nut torque is different when a lube like Never-Seez is used.
 
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