Number of Threads Engaged on a Lug

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quantum

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Is there any place in the code that states how many threads need to be engaged on a nut when securing a lug to a stud? The cables in question are current carrying conductors. I've had no luck locating anything yet.
 
quantum said:
Is there any place in the code that states how many threads need to be engaged on a nut when securing a lug to a stud? The cables in question are current carrying conductors. I've had no luck locating anything yet.
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Try the manufacturer. It may be part of the lug's listing.
 
quantum said:
Is there any place in the code that states how many threads need to be engaged on a nut when securing a lug to a stud? The cables in question are current carrying conductors. I've had no luck locating anything yet.
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I would say that the stud would have to extend past the nut or at least be flush.
From what I have been taught, to get the proper tighening strength, the length the nut needs to be engaged is at least the width of the bolt.
Fo example, a 1/4" bolt would need 1/4" of thread in the nut. Most nuts are about the thickness of their bolt threads.
 
quantum said:
Is there any place in the code that states how many threads need to be engaged on a nut when securing a lug to a stud? The cables in question are current carrying conductors. I've had no luck locating anything yet.
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We dealt with consultants and some had "interesting" specifications.
One for a project for the Middle East. Seven variable speed drives, all 1MW plus.
About five pages of electrical performance requirements - and a 40-page section on how to make the packing cases for shipping them. Including the "correct" angle to drive the screws in.
But back to your topic. Bolted connections had to have two visible threads protruding beyond the nut. And the mandatory number and type of washers had to be adhered to.
 
petersonra said:
I think as long as the torque is correct it probably does not matter.
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No the threads need to be past the fastener, I can't find the why but its probably to develop the correct torque and not deform the threads.
In the naval nuclear power program we allowed three threads.
 
tom baker said:
No the threads need to be past the fastener, I can't find the why but its probably to develop the correct torque and not deform the threads.
In the naval nuclear power program we allowed three threads.
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that is a naval nuke requirement perhaps.

if it is able to develop the correct torque what difference would it make?
 
tom baker said:
No the threads need to be past the fastener, I can't find the why but its probably to develop the correct torque and not deform the threads.
In the naval nuclear power program we allowed three threads.
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Three is the number I've heard in the past, but I couldn't recall/find a source. That's why I suggested checking the listing to see if the instructions might lend insight.
 
5 full threads engaged is our company standard, which pretty much means 2 threads showing.
 
ASME B31.3, 335.2.3 "Bolt Length. Bolts should extend completely through their nuts. Any which fail to do so are considered acceptably engaged if the lack of complete engagement is not more than one thread."
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There are several national specs that say something like this.
 
Wouldn't the first step be to determine what the minimum size of fastener is required?

If you have a 3/8" bolt/nut when a 3/16" would have been sufficient you may not need as many threads engaged as you would have needed for the 3/16 bolt.

I would think the characteristics of the fastener come into play in determining minimum required as well - hardness, type of metal (alloy) number of threads per inch, etc.
 
kwired said:
Wouldn't the first step be to determine what the minimum size of fastener is required?

If you have a 3/8" bolt/nut when a 3/16" would have been sufficient you may not need as many threads engaged as you would have needed for the 3/16 bolt.

I would think the characteristics of the fastener come into play in determining minimum required as well - hardness, type of metal (alloy) number of threads per inch, etc.
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That seems like over thinking it to me, but then the whole thread seems kind of like over thinking.

I gotta ask - If the OP is worried about having enough threads engaged, why not just get a longer bolt?
 
along with the size of the bolt and number of threads past the nut, the grade of the hardware is important too, especially for heavy loads or rigging. grade 5 I think is standard those some things require an 8 or 10. I've even seen grade 11, they were titanium alloy, with a breathtaking price.

For conduit fittings, two threads is enough. Look how thin locknuts are.
 
steve66 said:
That seems like over thinking it to me, but then the whole thread seems kind of like over thinking.

I gotta ask - If the OP is worried about having enough threads engaged, why not just get a longer bolt?
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That's much too sensible here.............:D
 
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