Grades of bolts for lug termination

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JJWalecka

JJWalecka

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New England
Is it grade 5 or 8 that should be used with Belleville washers for lug, busbar transformer terminations?

Can you please provide a chart or reference material that states this?

Thx
 
I used 304 SS. I never considered the need for grade 5 or 8. but I didn’t do a lot of transformer connections. Does the transformer mfg have a requirement?
 
Any of the above should be fine, but I would say avoiding grade 2 is wise, too easy to shear off.
 
If the torque is above 18lbft i use 8's. Even 5's will snap.
Now you can use grade 5 but you would need to have the correct length unthreaded portion of the stud because its the thread that makes it weak.
Thats why generally any configuration of grade 8 is a guarantee that it will hold forever because you dont need the exact length..
I even stock grade 8 1/4-20's as well- execpt for piddly non crictical stuff..
What is my concern is a rookie cranking a cheap bolt on the lug and stressing it where one good knock on the gear will snap it.. seen it!
 
tom baker said:
I used 304 SS. I never considered the need for grade 5 or 8. but I didn’t do a lot of transformer connections. Does the transformer mfg have a requirement?
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Tom, I advise against the use of stainless steel in most applications. Aluminum and stainless are a very poor combination, being far apart in the galvanic series. Stainless is also subject to galling, not nearly as strong, and more expensive so I just really can't see any reason to use it.

I don't think grade 5 versus grade 8 really makes much of a difference. I do like high quality hardware though and grade 8's are pretty 😍
 
electrofelon said:
Tom, I advise against the use of stainless steel in most applications. Aluminum and stainless are a very poor combination, being far apart in the galvanic series. Stainless is also subject to galling, not nearly as strong, and more expensive so I just really can't see any reason to use it.

I don't think grade 5 versus grade 8 really makes much of a difference. I do like high quality hardware though and grade 8's are pretty 😍
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Good comment. But I always use antiseeze on SS. The first CT install I did the POCO required silicon bronze fasteners for the CT lugs
 
rambojoe said:
If the torque is above 18lbft i use 8's. Even 5's will snap.
Now you can use grade 5 but you would need to have the correct length unthreaded portion of the stud because its the thread that makes it weak.
Thats why generally any configuration of grade 8 is a guarantee that it will hold forever because you dont need the exact length..
I even stock grade 8 1/4-20's as well- execpt for piddly non crictical stuff..
What is my concern is a rookie cranking a cheap bolt on the lug and stressing it where one good knock on the gear will snap it.. seen it!
Click to expand...
It seems to me that minimizing the unthreaded length will minimize elongation for any given tension, but, applying the weakest link of chain principle, it should have no effect on the failure tension. Any thread at all will be the potential failure point.
 
As I understand it, the only thing that really matters is that you use a torque wrench. The manufacturers instructions will tell you what to torque it at and you can look at the spec of the bolts to see if the bolt is up to it. I think you will find that you are properly twerking these things you won't break them off. I think you will also find that you need two or three threads past the nut to get a proper connection.
 
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