# Alright. Who ACTUALLY torques their screws…



## Almost Retired (Sep 14, 2021)

i am aware of what you are talking about, proper torque does not feel correct
if you have ever worked on buss bars with bell washers, then that is the perfect example
on a buss bar with bell washers, you dont completely flatten the cupped/bell washer so that it becomes a spring that continuously keeps the connection tight at any temp

my mill had a case where a heat survey showed a Very hot point on the buss bars for a very large VFD
visual inspection showed the bell washer was flattened, more over torquing did not fix it, we had to replace the bell washer and torque it properly

60*C is 140*F ,,, 75*C is 167*F ,,, 90*C is 194*F which is nearly boiling
all of these are above normal ambient temp

when you over tighten a screw, the conductor gets crushed as it heats up, consequently it becomes too loose when it cools
you are supposed to leave room for heat expansion when you tighten a screw

to answer your question, i always get it as tight as i can in a resi panel. no torquing


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## 205490 (Jun 23, 2020)

A few AHJ's here require it to pass final.


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## joe-nwt (Mar 28, 2019)

I do on bus connections, high current applications, etc. Never have on a breaker or device.


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## matt1124 (Aug 23, 2011)

In the bad parts of town I use #2 aluminum for the service conductors. When I realized I was changing the gauge of the wire with the milbank lay-in style lugs, I started torquing them. Yes, they seem loose to me that way.

otherwise, if I’m in an unfamiliar territory and don’t know how anal they are, i swipe across the lugs with my red torquing sharpie so inspectors know it’s been tightened down


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## SWDweller (Dec 9, 2020)

I do on all bus connections. As for screws I believe I have been doing this long enough that I do not need to own a torque screw driver (50 years). Thought about finding the right torquer used by plumbers but never finished looking. To many sizes and to many values. I stick to the calibrated wrist


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## Almost Retired (Sep 14, 2021)

matt1124 said:


> In the bad parts of town I use #2 aluminum for the service conductors. When I realized I was changing the gauge of the wire with the milbank lay-in style lugs, I started torquing them. Yes, they seem loose to me that way.
> 
> otherwise, if I’m in an unfamiliar territory and don’t know how anal they are, i swipe across the lugs with my red torquing sharpie so inspectors know it’s been tightened down


AL is much more susceptible to heat expansion and there for needs torquing more than CU


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## wiz1997 (Mar 30, 2021)

Worked at the South Texas Nuclear Plant back in the 80's.

We had to sit through a class on how to properly torque bolts.

Instructor stated the average guy with a 9/16" socket and a standard socket handle could easily put 40 plus foot pounds of torque on a 3/8" concrete anchor bolt.

30 foot pounds is what they wanted.

Seem a bit light to all of us.

Over torqueing stretches the bolt and can deform the threads.


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## backstay (Feb 3, 2011)

Average guy? Is that one who sits behind a desk or one that cranks on bolts all the time?


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## HertzHound (Jan 22, 2019)

My teeth start to chatter when I hit the right torque.


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## readydave8 (Sep 20, 2009)

I've considered torque screwdriver but haven't been running into problems that it might have prevented


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## kb1jb1 (Nov 11, 2017)

How does oxide inhibitor or anti seize on bolts affect the torque values?


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## Almost Retired (Sep 14, 2021)

kb1jb1 said:


> How does oxide inhibitor or anti seize on bolts affect the torque values?


i have read that it is a no no ,,, if you want the correct torque


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## kb1jb1 (Nov 11, 2017)

Almost Retired said:


> i have read that it is a no no ,,, if you want the correct torque


So let the lugs oxidize and you will never be able to open them .


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## aidonius (Jul 10, 2018)

kb1jb1 said:


> How does oxide inhibitor or anti seize on bolts affect the torque values?


You will get a greater amount of bolt tension for the same torque when the bolt is lubricated. I think you are generally supposed to reduce the torque by 25% when the bolts are lubricated but it depends on what lubricant and who you ask.
These people say 25% but also that you should consult your friendly neighbourhood engineer to do the math. https://www.antiseize.com/PDFs/torque_specifications.pdf


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## kb1jb1 (Nov 11, 2017)

So much for anti seize.


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## CAUSA (Apr 3, 2013)

I do,

I own 8 torque wrenches.
-fixed 6 inch pound, 1/4” drive.
-fixed 12 inch pound, 1/4” drive.
- 4 to 45 inch pound. 1/4” drive
-5 to 50 foot pounds 3/8” drive.
-30 to 250 foot pounds 3/8” drive.
- 50 to 450 foot pounds 1/2” drive.
-100 to 850 foot pounds 1” drive.
-0 to 200 digital foot pounds 3/8” drive.

And I use them all.
One thing to note on torque. If there is any corrosion, impurities, chemical reactions. This will affect the frictions in the mating surface. And it will pre-maturely reach the torque limit. This does not mean that the clamping force has been reached.

keep surfaces clean and use the proper washer for the materials and design.

torque is the best established estimate that we have so far.

And if you add any extension or angles it will change your torque value. Do not over torque.

I added a for link for the extension explanation.



https://www.terex.com/docs/librariesprovider7/tech-tips/techtip_53.pdf?sfvrsn=1371ae74_10


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## CAUSA (Apr 3, 2013)

On lubricant,

there are some situations that you will add lubricant to the threads.

example , dampers on a crankshaft, manufacturer requests that 15w40 oil be used for assembly and torquing.

On a 32”flange to use anti-seize to increase clamping force and to stretch the studs.

some situations require it and some do not.

Boils down to.

know what your working with, and disassemble/assemble with care.


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## gpop (May 14, 2018)

Helper got a torque screwdriver as punishment after he went farm tight on a vfd terminal and tore it off the drive.


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## CMP (Oct 30, 2019)

Heck, I thought that everybody nowadays just used the clutch on their impact driver. Now I don't feel so old cause I just use my old school wrenches and drivers.


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## bill39 (Sep 4, 2009)

When this topic has come up in other posts I have mentioned that we need to remember that these torque tools need to be calibrated periodically. The documentation said it needed calibrated every X number of months, not X number of uses. So you can’t just leave them laying around on the shelf. 

In my experience, it was cheaper to buy new torque screwdriver sets than pay for shipping the old ones back and forth. Buying new probably wouldn’t apply for a 3/8” or 1/2” torque wrenches.

While I realize torquing is required even on small panel terminals, switches, & receptacles I think it is overkill on low current devices.….. and we wonder why USA made products cost more than Chinese crap.


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## paulengr (Oct 8, 2017)

kb1jb1 said:


> How does oxide inhibitor or anti seize on bolts affect the torque values?


I’ve read that “thread lubricants” including never seez and even loctite help make torque more even. It doesn’t increase or decrease “torque”.


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## micromind (Aug 11, 2007)

I can't remember using a torque wrench on anything electrical.


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## paulengr (Oct 8, 2017)

CAUSA said:


> I do,
> 
> I own 8 torque wrenches.
> -fixed 6 inch pound, 1/4” drive.
> ...


I call BS.

Two reasons you can get torque loss. One is if you don’t keep everything on the same axis. Then just like a swivel you will lose torque.

Second reason is there is some elasticity in the extension. So in theory some of the torque goes into twisting the extension metal. I’m not talking about slop in the less than perfect joints. I’m talking about even if you have a solid extension it will twist. But tool steels are very hard so that is minimal by nature.

So here’s a YouTube video demonstrating how much loss you actually get. Basically if it’s there it’s not measurable.






As to electrical, there’s a good reason going crazy on torque is overkill despite tons of claims to the contrary. In an electrical joint do you think that if you have say two 1” bus bars that overlap 1” that you get 1 square inch of contact? Not even close! All electrical alloys have an oxide coating on the surface. When you squeeze the two surfaces together you crack the oxide and then you mix the two metals together in a cold weld. But it’s not the entire surface…it never is. Only what they call alpha spits actually make metal on metal contact. As you squeeze further more alpha spots form and the existing ones grow a little but only a small fraction of the surface is actually making contact. And it’s diminishing returns. If you hit about 80 PSI you’ve done about all you can do. The resistance in a joint NEVER gets close to the bulk conductor resistance.

Now if you loosen things something interesting happens. It has hysteresis…the alpha spots are true welds. Resistance readings stay about the same until just before the joint falls apart. In addition the coefficient of expansion is 11-13 for aluminum alloys, 9-10 for copper alloys, and around 6-7 for steels for a 10 F temperature rise. So copper and aluminum expand at a faster rate than steel, actually increasing the force in a joint when it heats up.

Now over in the structural world they have come up with some much better ways of doing torquing. Specifically measuring joint tension. They have some special bolts that change color on the head and they have “squirter” washers that squirt out some colored stuff when you hit the right tension. This is vastly better than torque and here’s why. About 80% of the torque is just overcoming thread friction. Only about 10% actually goes into joint compression. So torque is a terrible way to measure things.

In practice joint failures are very rare. If it was truly a problem we would have much higher failure rates.


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## kb1jb1 (Nov 11, 2017)

paulengr said:


> I call BS.
> 
> Two reasons you can get torque loss. One is if you don’t keep everything on the same axis. Then just like a swivel you will lose torque.
> 
> ...


You always come up with some interesting factoids. Sometimes it get a bit to technical for me but welcomed just the same. Maybe dumb it down sometimes.


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## macmikeman (Jan 23, 2007)

Loose connections cause the majority of electrical fires. This has nothing to do with the fact that I bought and use a torque screwdriver to make device connections. My hand connections before using a torque screwdriver were just about exactly the same pressure as my tool shows me now. It's because if I am in court I can faithfully testify I used my torque driver to tighten my connections on the device screws. And that, ladies and Jellybeans is called covering your ass.......


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## CAUSA (Apr 3, 2013)

paulengr said:


> I call BS.
> 
> Two reasons you can get torque loss. One is if you don’t keep everything on the same axis. Then just like a swivel you will lose torque.
> 
> ...


So what term are you using BS as?
1- British standards?
2- Bachelor of science?
3- untrue talk?

so there is no mention of items 1 or 2, so it has to do with item 3!

ok so What part of the post is untrue???


I agree with all the items you mentioned but no mention of grading of materials. Over torque a material not rated for the friction and clamp force and yes it will fail.

so is it the torque extension formula, to calculate the readjustment to prevent over torque?

What about bar flex in the torque application?

In all measurements there is always a +- to the reading. So we have to say that torque is the best estimate. Best as in cheap and tried tested and accepted throughout all the world. Is this untrue?

Or is it the fact that, I spent 10s of thousands of dollars in the 35years in the multiple trades over the years on calibration and tools?

when you call someone out for being untrue.

try to be specific on the area that is untrue.


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## oldsparky52 (Feb 25, 2020)

SWDweller said:


> I do on all bus connections. As for screws I believe I have been doing this long enough that I do not need to own a torque screw driver (50 years). Thought about finding the right torquer used by plumbers but never finished looking. To many sizes and to many values. I stick to the calibrated wrist


My wrists used to be powerful and I overtightened ever breaker connection lower than #2 wire for all of my working life. I wonder how many fires I started.


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## oldsparky52 (Feb 25, 2020)

CAUSA said:


> I do,
> 
> I own 8 torque wrenches.
> -fixed 6 inch pound, 1/4” drive.
> ...


Do you have them calibrated and if so, how often?


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## CAUSA (Apr 3, 2013)

oldsparky52 said:


> Do you have them calibrated and if so, how often?


The smaller ones, once a year.
To keep cost down.
the large ones, a month before the job completion and work it in to the costing of the job certification/commissioning process.

very costly to do them all at the same time.


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## paulengr (Oct 8, 2017)

CAUSA said:


> So what term are you using BS as?
> 1- British standards?
> 2- Bachelor of science?
> 3- untrue talk?
> ...


As far as materials sure I can twist a nylon bolt right off or strip out aluminum parts easily. Overtorquing is an issue. It’s an issue if I take a 1/2” drive 200 ft-lb impact wrench and use it on 1/4” bolts. I can snap the heads off like snapping the ends off beans.

My point about extensions is that yes I will agree there is torque loss but at the torque required the torque loss is within the accuracy of the tool. Frequently electricians must work with stupidly long drivers and extensions because the fasteners are intentionally recessed (guarded) to prevent accidental contact. So saying that you can’t use extensions because of accuracy problems is simply untrue. Sure the torque loss formulas exist but when it is within the accuracy limit of the tool so we need to apply a 1% adjustment to a tool that is at best accurate to 2% immediately after calibration? And how many are actually calibrated every few hundred uses? So my point is that the extension argument is typical engineering noise. If I routinely put capacitors on every three phase motor for power factor correction I can reduce power bills, too. But you will never see a change on your bill for usage (demand is another matter!!)

Even with a torque wrench the actual fastener force accuracy is +/-25%. This has been documented repeatedly. This is as opposed to +/-50% which is often reported for hand tightening. So this is like using a vernier caliper to measure the length to cut green lumber that has not been kiln dried….measuring the wrong thing that is only vaguely sort of related to what we need. We align motors with Babbitt bearings to ISO standards which often call for 1-2 mil accuracy. You can visibly see it change by several mils just by tightening the base bolts on a motor. That’s where precision and torque wrenches (granted it might be 3 feet long with a 3:1 torque multiplier) matter.

There are times where more precision is required. On high torque mechanical connections for instance super bolts and super nuts do a great job. Using ultrasonic length measurement allows very precise control over bolt tension and thus pressure measurement knowing the modulus of elasticity. A lot of structural jobs now require various pressure indicating washers. It’s not that they need the precision but they need the assurance.

The vast majority of electrical work is simply not that accurate and doesn’t need to be. There are exceptions. One that comes immediately to mind is mounting power electronics. You need a specific amount of pressure to hold an SCR or IGBT or similar devices. The range of pressure required really doesn’t even work well with torque wrenches. The most reliable techniques involve using hydraulic instrumented rams or using the torque wrench to snug a fastener then turn a specific amount of turns (turn of nut technique) to apply a very specific amount of bolt stretch. Turn of nut works about 80% of the time.


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## Yankee77 (Oct 5, 2020)

paulengr said:


> I’ve read that “thread lubricants” including never seez and even loctite help make torque more even. It doesn’t increase or decrease “torque”.


I agree.
One would think 10 ft/lbs is 10 ft/lbs, regardless if it has peanut butter and jelly on it. What weighs more 100 lbs of steel or 100 lbs of feathers?


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## joe-nwt (Mar 28, 2019)

The easiest method to obtain the proper torque is with a paint marker.


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## paulengr (Oct 8, 2017)

macmikeman said:


> Loose connections cause the majority of electrical fires. This has nothing to do with the fact that I bought and use a torque screwdriver to make device connections. My hand connections before using a torque screwdriver were just about exactly the same pressure as my tool shows me now. It's because if I am in court I can faithfully testify I used my torque driver to tighten my connections on the device screws. And that, ladies and Jellybeans is called covering your ass.......


Everything gets blamed on looseness but it’s just poor forensic analysis. Every time you inspect a failed connection it will be “loose”. If I put torque on a terminal I’m putting stress on it. It acts like a spring. The metal crystals actually unwind themselves and you can see it under a TEM microscope.











As you heat metals they anneal…they relax and stress relieve themselves. The crystals reform their chemical bonds in new configurations to eliminate the stress we created in the metal. We are NOT melting anything here and annealing goes on even at room temperature. If you have a torque wrench try this. Tighten a bolt to torque. Come back tomorrow and see how much farther you can turn it. It will lose a surprising amount of torque, imagine what happens above room temperature.

Now if I heat up a connection it will anneal the metal. All those dislocations we put into the crystals will disappear much faster. So now my connection is loose. And any temper is lost and allots that harden under heat and case hardened are now over hardened and brittle. Although the drama you hear about loose connections isn’t as dramatic as you hear, it will lose tension raising the resistance. If we are already overheating a joint this can create a looseness/overheating thermal runaway. Plus even if none of this happened except with solid core cables there are air gaps between strands. If a cable partly melts those air gaps close up as the cable shrinks. The mechanical compression reduces this but it’s not gone.

This all sounds like I’m making a case for looseness. The end result of every joint failure is ALWAYS looseness. But how it got there is not the case. If someone undersizes a cable or say with 3 conductors per phase puts them in conduit AAA, BBB, CCC, or cuts strands or uses the wrong lug or insulation is partly or fully under the contact point or there is contamination, corrosion, fretting, or pulling so hard on the cable it stretches or pulls out or anything else happening that causes a joint failure will appear in the burned and melted carcass that remains. Often the cable is so loose you can pull it right out. That doesn’t mean it was ever loose to start with though.

Finally as I said earlier electrical contacts have a lot of hysteresis. This is easy to see with a micro-ohm meter and a wrench but high accuracy Kelvin bridges are very expensive. In a decent mechanical lug you might see 50-250 micro-ohms of resistance if properly installed. The resistance is high at first and drops but then you quickly reach diminishing returns as you tighten. Now as you loosen though it will NOT simply return to the same value. The points where we made intimate true metal-on-metal contact are true welds with chemical bonds and don’t want to break loose. So it takes a much looser joint than it did tightening to reach the same contact resistance. Last weekend I was testing breakers. Some were truly awful in terms of contact resistance for various reasons. On good new ones I usually get around 50-150 micro ohms on draw outs over about 1000 A. As they get worn or pitted contact resistance goes up to 250-350. These were in rough shape. Some were around 1 milliohm and when that happens the contact resistances were wildly uneven and contact tips shot. One actually hit 1 ohm. Yes, 1,000,000 micro ohms. This isn’t measurement errors. When we get “bad” results we clean and reseat the probes just to make sure it’s not just a loose meter issue. I checked the one ohm contact including tripping and reclosing the breaker. Yet the plant was running just fine and these ticking time bombs were silently failing. But the point here is that even with extremely bad contacts these 800-2000 A breakers were still operating. It takes a LOT of looseness to fail a connection.

So I don’t believe that looseness is actually the major problem with connections. It’s just poor connections from poor technique. It is also easily preventable and you don’t need a torque wrench. That is just one issue.

I believe in doing every termination as good as possible but even if you can do 99% right, nobody cares. They only care about the 1% that are wrong. Give every cable a good tug. Look in the ends of mechanical lugs. On questionable ones if possible remove the set screw and look. Pay attention if all set screws are the same depth once tightened. Hold the wire in your hand, NOT pliers. Do you feel or see it move as the lug starts to load up tension? Does it feel like it “bottomed out”? Can’t tell this with a torque wrench. If you actually used a stripping gauge like you are supposed to is the amount of bare copper sticking out the same on every lug? After tightening do you go back and put a little tension on each one to check? The amount of extra time here is minimal but your 99% can get to 99.99%.


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## CAUSA (Apr 3, 2013)

See below in your post.




paulengr said:


> As far as materials sure I can twist a nylon bolt right off or strip out aluminum parts easily. Overtorquing is an issue. It’s an issue if I take a 1/2” drive 200 ft-lb impact wrench and use it on 1/4” bolts. I can snap the heads off like snapping the ends off beans. Yes, I hate when a grade 8 bolt shears like a grade 5 bolt torque setting.
> 
> My point about extensions is that yes I will agree there is torque loss but at the torque required the torque loss is within the accuracy of the tool. Frequently electricians must work with stupidly long drivers and extensions because the fasteners are intentionally recessed (guarded) to prevent accidental contact. So saying that you can’t use extensions because of accuracy problems is simply untrue. (I did not intend to imply this assumption.) Sure the torque loss formulas exist but when it is within the accuracy limit of the tool so we need to apply a 1% adjustment to a tool that is at best accurate to 2% immediately after calibration? And how many are actually calibrated every few hundred uses? So my point is that the extension argument is typical engineering noise. (It is meant to adjust the tool setting to accommodate the length of extension, to try to have some level of accuracy to the torque procedure. To not over torque or under torque.) If I routinely put capacitors on every three phase motor for power factor correction I can reduce power bills, too. But you will never see a change on your bill for usage (demand is another matter!!)
> 
> ...


This is not meant to be disrespectful in any way please read objectively.


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## CAUSA (Apr 3, 2013)

For those interested in other torque adapter design.



https://www.jimsusa.com/wp-content/uploads/2019/09/922-IS.pdf



note: the formula is for tool settings adjustment, for the error rate that can be encountered. Whenever using extensions. This can be in the over or under torque range.


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## matt1124 (Aug 23, 2011)

Yankee77 said:


> I agree.
> One would think 10 ft/lbs is 10 ft/lbs, regardless if it has peanut butter and jelly on it. What weighs more 100 lbs of steel or 100 lbs of feathers?


Feathers. You have to live with the weight of what you did to those poor birds.


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## emtnut (Mar 1, 2015)

I know I've told this story before, but it's true and relevant.

When the trucking industry mandated the torquing of wheel lugs, that's when wheels started flying off of the trucks 

Engineers sat down (again), and then said you need to re-torque 1 week later.
Still some wheels falling off.
Engineers sat down (Again !), and came up with the visual markers for the circle check .

I'll stick with goot and tighten.


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## micromind (Aug 11, 2007)

emtnut said:


> I know I've told this story before, but it's true and relevant.
> 
> When the trucking industry mandated the torquing of wheel lugs, that's when wheels started flying off of the trucks
> 
> ...


Whenever the words 'mandate' and/or 'engineer' appear, disaster will almost always follow.


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## Greg Sparkovich (Sep 15, 2007)

CMP said:


> Heck, I thought that everybody nowadays just used the clutch on their impact driver. Now I don't feel so old cause I just use my old school wrenches and drivers.


That's close to what I do. I only do residential, so twerking is mostly in panels. I measured proper torque and then used the torque setting on my cordless drill to match for different sizes / lbs. per inch. So, for example: in my 100 amp panels, circuit breakers are torque setting "5" and feeders are "8". I wrote the torque values on the drill so I wouldn't forget. I spot check a few connections with the torque wrench for every panel, but so far battery drain does not seem to affect torque values (unless of course the battery is so obviously drained that it's not properly functioning anyway).


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## kicmeinjimmy (Aug 9, 2013)

I hear you should have on truck. My one eye spins when right. I go to inspectors meetings. They do bring up on occasion. They even have said outlets as well now.


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## CAUSA (Apr 3, 2013)

Just though that I would show the latest addition to the collection. A, T Handel preloaded 6#. Will be great and fast for all those connections that require the 6# touch.

got it from a motor company on sale. Very good price.








Can be calibrated and comes with manufacturer certification for preloads setting.


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## Wirenuting (Sep 12, 2010)

Ok so it’s,

insert, torque, wiggle, torque, wiggle, torque?

Go get coffee?

asking for a friend.


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## CAUSA (Apr 3, 2013)

Wirenuting said:


> Ok so it’s,
> 
> insert, torque, wiggle, torque, wiggle, torque?
> 
> ...


No,

First coffee, order the apprentice to tighten all the connections. Finger tight. Watch him look at you shaking his head.

after he is done you pull out the T Handel and put on the right bit. And work it like a ratchet till it hits the preload limit and then move on to the donut. And finish the coffee.


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## Wirenuting (Sep 12, 2010)

CAUSA said:


> No,
> 
> First coffee, order the apprentice to tighten all the connections. Finger tight. Watch him look at you shaking his head.
> 
> after he is done you pull out the T Handel and put on the right bit. And work it like a ratchet till it hits the preload limit and then move on to the donut. And finish the coffee.


Luckily I’m old enough to feel the arthritis click as I reach the correct value.


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## kicmeinjimmy (Aug 9, 2013)

I thought the eye twirl was good, I'm 53 arthritis click works to. Lol


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## Slay301 (Apr 23, 2018)

kb1jb1 said:


> So much for anti seize.


It’s a wasted step anyway just get a lug that’s aluminum rated anyway


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## brian john (Mar 11, 2007)

I have been using a torque wrench since the mid 70's, BUT on small gauge wires particularly in terminal blocks, receptacles, and switches, I think the push for torquing is overblown. If this was a real issue there would be a heck of a lot more fires from overtightened connections. 

When I worked we had customers that insisted on torquing all connections so we complied.


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