# Help with torquing



## Hendog (Mar 24, 2020)

When trying to torque the main breaker on a 100 amp panel the slotted lugs strips out. Not the threads but the stright slot. My torque screwdriver just goes up to 40 inch pounds but the breaker requires 50 inch pounds. When I try to finish it off with my 1/4" torque wrench it damages the stright slot. Should I be able to order replacement lugs from Schneider? I may try to find a torque screwdriver that goes up to 50 inch pounds. Any suggestions?


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## paulengr (Oct 8, 2017)

Hendog said:


> When trying to torque the main breaker on a 100 amp panel the slotted lugs strips out. Not the threads but the stright slot. My torque screwdriver just goes up to 40 inch pounds but the breaker requires 50 inch pounds. When I try to finish it off with my 1/4" torque wrench it damages the stright slot. Should I be able to order replacement lugs from Schneider? I may try to find a torque screwdriver that goes up to 50 inch pounds. Any suggestions?



50 is a bit much for a screwdriver. Use a bit with a 1/4” or 3/8” socket and then a standard torque wrench. This also lets you hold pressure on the end of the wrench so that the socket doesn’t slip.

In the old days we’d take a saw and reslot it. But obviously not allowed on Code jobs.


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## VELOCI3 (Aug 15, 2019)

Put penetrox or similar conductive compound on the lug threads. They will not bind up as much and also will give you a more accurate torque value. 


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## Hendog (Mar 24, 2020)

Wouldn't that affect the torque value? A hex screw instead of a stright slot would be a much better option IMO.


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## VELOCI3 (Aug 15, 2019)

Use what the manufacturer gave you. Also use a slotted blade that is the same or larger than the slot on the lug. The closer you are to the thickness and width of the slot will better the tools grip. 


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## splatz (May 23, 2015)

VELOCI3 said:


> Use what the manufacturer gave you. Also use a slotted blade that is the same or larger than the slot on the lug. The closer you are to the thickness and width of the slot will better the tools grip.


I agree, with slotted fasteners, a good fit is the key to getting good torque without cam-out or damage to the slot. If slotted tips fit as well as hex sockets they'd work almost as well, but you don't see people running around with a set of slotted bits in 1/64" increments like you do with hex bits. 

Also, slotted bits are usually ground so the tip is tapered, which is obviously going to make it want to cam out as the torque gets higher. They make screwdrivers that are ground with little or no taper and they work much better, gunsmiths look for these. 

Try a 1/4" socket in your torque wrench and try a bunch of different good quality hex shank slotted bits, with a little luck you'll find one that fits just right in the slot and doesn't want to cam out or mangle the set screw slot.


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## gpop (May 14, 2018)

when im working as the lower end of the torque range on a tool i like to test it on the bench a few times first to get a idea of what it feels like. On slots i also like to use snap on bits as they have teeth cut into the tip which gives a little extra grip.


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## JoeSparky (Mar 25, 2010)

My torque wrenches have 2 settings:
M12 Surge for smaller stuff 100a and less
18v Ryobi Impact for larger stuff over 100a
:devil3:


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## Kevin (Feb 14, 2017)

JoeSparky said:


> My torque wrenches have 2 settings:
> M12 Surge for smaller stuff 100a and less
> 18v Ryobi Impact for larger stuff over 100a
> :devil3:


I was taught tighten till you hear it crack, then back a quarter turn. 

Not really, I was taught to tighten them by feel. I am the torque wrench! Maybe if I did commercial I would own a torque wrench, but we only do residential so if the boss says we don't need one, we don't. 

Sent from my new phone. Autocorrect may have changed stuff.


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## Hendog (Mar 24, 2020)

Kevin_Essiambre said:


> I was taught tighten till you hear it crack, then back a quarter turn.
> 
> Not really, I was taught to tighten them by feel. I am the torque wrench! Maybe if I did commercial I would own a torque wrench, but we only do residential so if the boss says we don't need one, we don't.
> 
> Sent from my new phone. Autocorrect may have changed stuff.


I've never torqued anything in 25 years but thought I would give it a try. Always thought I was over torquing everything.


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## HackWork (Oct 2, 2009)

I am a little confused here. I just looked up a Siemens 100A panel and it says to make the feeder lugs 110inlbs, including the A and B phase on the main breaker: https://images.homedepot-static.com/catalog/pdfImages/fd/fd7d62eb-54a8-4796-835d-e0a0a5c7e85a.pdf

So how is 50inlbs stripping the head? 

Using a large screwdriver I have put a hell of a lot of torque on older straight screw head lugs to break them. Could it be bad lugs in the OP's situation (as in soft metal)?


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## Kevin (Feb 14, 2017)

Hendog said:


> I've never torqued anything in 25 years but thought I would give it a try. Always thought I was over torquing everything.


This discussion has come up before. If you torque the lugs as tight as the manufacturer says to on the older aluminum wiring from the 70's, there won't be anything left of the wire because it's so soft compared to today's aluminum wire.

Unless my boss tells me otherwise, I will continue with my hand torque method. Over 200 services without an issue, so it must work.

Sent from my new phone. Autocorrect may have changed stuff.


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## HackWork (Oct 2, 2009)

Hendog said:


> I've never torqued anything in 25 years but thought I would give it a try. Always thought I was over torquing everything.


Yeah, I was always under the impression that the specced torque was too loose.


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## macmikeman (Jan 23, 2007)

One of the few times I torqued in a 100 amp breaker properly with a torque wrench, I got scolded by a field captain from the poco cause he says to me the conductor almost fell out when he tugged on it. After that I'm back to my good old method- till it is as tight as it will go by hand. Then shake the wire, and tighten some more. 




Brian John is gonna be really pissed off to read this I just know it. 


Those posted torque numbers from the manufacturer's are probably coming from tech's who smoke dope on a regular basis....................


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## VELOCI3 (Aug 15, 2019)

HackWork said:


> Yeah, I was always under the impression that the specced torque was too loose.



Wrong torque shows up in IR scans and you’re right it does seem too loose. Last breaker I torqued was a SD 2000 amp and it showed 35 ft lbs on the sticker. Felt loose. It’s on the IR list for next year so let’s see if it passes. 


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## gpop (May 14, 2018)

VELOCI3 said:


> Wrong torque shows up in IR scans and you’re right it does seem too loose. Last breaker I torqued was a SD 2000 amp and it showed 35 ft lbs on the sticker. Felt loose. It’s on the IR list for next year so let’s see if it passes.
> 
> 
> Sent from my iPhone using Tapatalk


New copper or aluminum is annealed so its hard to really say torque is correct when the material changes over time. (new wire bends easier then old wire).

The guy who trained me insisted that we torque then leave for a few hours then back off and torque again. he said that gave the wire time to relax. Either way it also meant that we got a extra quarter to half turn with out breaking the rules.


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## Kevin (Feb 14, 2017)

gpop said:


> New copper or aluminum is annealed so its hard to really say torque is correct when the material changes over time. (new wire bends easier then old wire).
> 
> 
> 
> The guy who trained me insisted that we torque then leave for a few hours then back off and torque again. he said that gave the wire time to relax. Either way it also meant that we got a extra quarter to half turn with out breaking the rules.


We do this with residential services. We land the wires in the lugs, then proceed to do other things while waiting for the POCO. When POCO shows up, we tighten them again before they liven it up.

Sent from my new phone. Autocorrect may have changed stuff.


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## varmit (Apr 19, 2009)

I have personally seen several instances where the manufacturer torque values would not work- either too loose to make good connection or would be so tight that the lug would break if pushed to the listed value. Sometimes a calibrated arm/hand is still the best method.

Note: If the lug threads are lubricated, this will lessen the torque value needed for proper tightness.

It seems that there is a variation in the hardness and compressibility of conductors that effect true torque values. Yes, screwdriver fit is very important for slotted screws. I have found some lug slotted screws, that even if correct tools and methods were used, the slotted head would distort.


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## splatz (May 23, 2015)

I have never had an issue in strictly mechanical stuff lubing threads, but I am afraid to do it with the set screws on lugs. Unless the manufacturer's instructions called for it. 

I feel like the friction in the threads is what's keeping that wire compressed, and lube works both ways. You'll compress the wire more at the spec'd torque with lube, but it will also spring back and loosen more easily. 

But then again, you always lubricate spark plugs before installing them and they are under quite a bit more stress than most lugs.


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## VELOCI3 (Aug 15, 2019)

splatz said:


> I have never had an issue in strictly mechanical stuff lubing threads, but I am afraid to do it with the set screws on lugs. Unless the manufacturer's instructions called for it.
> 
> I feel like the friction in the threads is what's keeping that wire compressed, and lube works both ways. You'll compress the wire more at the spec'd torque with lube, but it will also spring back and loosen more easily.
> 
> But then again, you always lubricate spark plugs before installing them and they are under quite a bit more stress than most lugs.



Spark plugs have a crush washer to secure it


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## Wirenuting (Sep 12, 2010)

gpop said:


> The guy who trained me insisted that we torque then leave for a few hours then back off and torque again. he said that gave the wire time to relax. Either way it also meant that we got a extra quarter to half turn with out breaking the rules.


For me it was tighten, wiggle the wire and retighten, repeat as needed. 
Then we go to a torque wrench and just torquing doesn't seem to be enough. 

Do we wiggle the wire to help seat or not?


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## TheLivingBubba (Jul 23, 2015)

Wirenuting said:


> Do we wiggle the wire to help seat or not?


I always give it two or three shakes, anything more and you're just playing with it. 

I've always wiggled copper out of habit.


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## just the cowboy (Sep 4, 2013)

Wirenuting said:


> For me it was tighten, wiggle the wire and retighten, repeat as needed.
> Then we go to a torque wrench and just torquing doesn't seem to be enough.
> 
> Do we wiggle the wire to help seat or not?


We are old school, we saw the results too many times by not wiggling it. 
If everything was great in real life and wires were perfect fit in line with lug then no. But wiggle seems to help realign wire.

Cowboy


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## HackWork (Oct 2, 2009)

Wiggle it, just a little bit...


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## mofos be cray (Nov 14, 2016)

VELOCI3 said:


> Put penetrox or similar conductive compound on the lug threads. They will not bind up as much and also will give you a more accurate torque value.
> 
> 
> Sent from my iPhone using Tapatalk


Accurate with relation to the force applied to the conductor but the torque wrench don't care, it breaks when it hits its spec. So lube will only affect the conductor and whether it is adequately affixed or not. It will not help a screw that is intended to be torqued to one value and breaks before reach that value. That's just crap manufacturing


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## paulengr (Oct 8, 2017)

mofos be cray said:


> Accurate with relation to the force applied to the conductor but the torque wrench don't care, it breaks when it hits its spec. So lube will only affect the conductor and whether it is adequately affixed or not. It will not help a screw that is intended to be torqued to one value and breaks before reach that value. That's just crap manufacturing



Torque wrenches don’t measure bolt/screw tension. They measure nut torque which is about 80% overcoming thread friction. Everybody is infatuated with torque wrench accuracy but miss the fact that it’s a lousy way to measure bolt tension. Thread lube of any kind helps overcome thread friction so it improves consistency. They do NOT get it looser or tighter but seem to help consistency. At the end of the pull the liquid will just get forced out of the joint anyway. I’ll throw in loctite and never seez too that also do a good job for other applications.

One thing that has been proven over time is that so called loc washers can either do nothing or at worst actually promote looseness. Most machine tests prove helical spring washers (split washers) make it worse. Belleville’s might help maintain pressure with heating/cooling. The wavy ribbon ones do nothing. The star washers promote cracking. Lock nuts whether nylocks, or various messed up threads all work but nylocks are less than max electrical temperatures. See NASA RP-1 or the bolttech web site.

The big thing torque wrenches do is make electricians more consistent in tightening. They do little else. There is an IAEA report that shows pros are not any better than amateurs at “feel”.


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## mofos be cray (Nov 14, 2016)

Sorry Paul, I'm afraid I dont understand what you mean by bolt tension as opposed to nut torque.


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## Kevin (Feb 14, 2017)

paulengr said:


> Torque wrenches don’t measure bolt/screw tension. They measure nut torque which is about 80% overcoming thread friction. Everybody is infatuated with torque wrench accuracy but miss the fact that it’s a lousy way to measure bolt tension. Thread lube of any kind helps overcome thread friction so it improves consistency. They do NOT get it looser or tighter but seem to help consistency. At the end of the pull the liquid will just get forced out of the joint anyway. I’ll throw in loctite and never seez too that also do a good job for other applications.
> 
> One thing that has been proven over time is that so called loc washers can either do nothing or at worst actually promote looseness. Most machine tests prove helical spring washers (split washers) make it worse. Belleville’s might help maintain pressure with heating/cooling. The wavy ribbon ones do nothing. The star washers promote cracking. Lock nuts whether nylocks, or various messed up threads all work but nylocks are less than max electrical temperatures. See NASA RP-1 or the bolttech web site.
> 
> The big thing torque wrenches do is make electricians more consistent in tightening. They do little else. There is an IAEA report that shows pros are not any better than amateurs at “feel”.


What about nord-lock lockwashers?

Sent from my new phone. Autocorrect may have changed stuff.


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## paulengr (Oct 8, 2017)

Kevin_Essiambre said:


> What about nord-lock lockwashers?
> 
> Sent from my new phone. Autocorrect may have changed stuff.



Yes and no.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900009424.pdf

See page 10. Also the bug version is on page 8. They work as far as some anti-loosening but they damage the surfaces and promote cracking and corrosion.

Self-loosening is due to the Jost effect. Essentially the bolt gets shaken so hard that it bounces. Then if you get a sideways torque it can twist a little as it lands. This can only happen if:
1. The bolt is undersized for the opening.
2. It is ridiculously loose. Properly torqued bolts cannot do this.
3, it is in shear vibration (sideways).

It’s trivially easy to ensure item 1 and 2. Just use the right size bolt (fill the hole) and torque to 85%+ of breaking strength.


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