Torquing bolted electrical connections

[hacim23]

Is there a general reference guide or book for torque values in electrical connections when the equipment does not have anything posted on it? Does it make a difference whether you torque on the nut side or the head of the bolt?

 

[zbang]

In general, look to the manufacturers; pretty much all of them publish torque numbers for their products. Which side you use depends on the particular bolts and equipment.

You didn't ask, but... you can only accurately measure torque when the wrench is turning. Among other things, don't use a "clicker" torque wrench on a bolt to see if it's up to spec after its already tightened. It's a popular technique but it's also wrong (then you're measuring stiction, which isn't what you want).

There have been a few topics here before on torquing bolts, the search will find them.

 

[Smart $]

Look in the back of your Code book...

Informative Annex I Recommended Tightening Torque Tables from UL Standard 486A-B

 

[K8MHZ]

In general, look to the manufacturers; pretty much all of them publish torque numbers for their products. Which side you use depends on the particular bolts and equipment.

You didn't ask, but... you can only accurately measure torque when the wrench is turning. Among other things, don't use a "clicker" torque wrench on a bolt to see if it's up to spec after its already tightened. It's a popular technique but it's also wrong (then you're measuring stiction, which isn't what you want).

There have been a few topics here before on torquing bolts, the search will find them.

Good info, right there.

 

[Cow]

Is there a general reference guide or book for torque values in electrical connections when the equipment does not have anything posted on it? Does it make a difference whether you torque on the nut side or the head of the bolt?

You want to torque the nut, not the bolt, if possible. You can imagine that a bolt through a misaligned hole may not have the proper clearances and grab slightly as it is turned. That takes extra torque to overcome that, and will give you a misrepresentation that you have achieved the proper torque when tightening.

 

[Fulthrotl]

In general, look to the manufacturers; pretty much all of them publish torque numbers for their products. Which side you use depends on the particular bolts and equipment.

You didn't ask, but... you can only accurately measure torque when the wrench is turning. Among other things, don't use a "clicker" torque wrench on a bolt to see if it's up to spec after its already tightened. It's a popular technique but it's also wrong (then you're measuring stiction, which isn't what you want).

There have been a few topics here before on torquing bolts, the search will find them.

all of that. also, depending on what you are torquing, if it's a
bolted connection, such as busbar, the SAE rating of the nut
and bolt can be used, provided that the nut, bolt, and washer
are all of the same SAE rating.

for example, a 1/2" coarse thread grade 2 bolt, and a 3/8"
grade 8 fine thread bolt have the same torque recommendation,
37 ft/lbs. the 1/2" bolt is what you will find in the bin at home
desperate, and the 3/8" one is what you'll find at an industrial
hardware store.

i've also twisted 1/2" ungraded bolts off with 37 ft/lbs. or they keep stretching
like they are made of string cheese. sometimes chinese threaded
hardware is not reassuring.

in my hypress lugs box, i also have 3/8"-24 grade 8 allen head cap
screws, washers, and nylocks, US made. oil on the threads, torque
to 37, and no problems.