screw/bolt material & torque

[cloonypan]

Hello,
I have a bolt as which need to be confirmed tighten torque. The said bolt picture is as enclosed. I need some help. Thank you.

http://files.engineering.com/getfil...69c2-4ca0-a21b-7de4034510d8&file=DSCN0933.JPG

 

[desertfox]

Hi cloonypan

I think we need a lot more information before we can give any guidance on a torque figure.

1/ Materials to be clamped and appropriate yield stresses

2/ Environment and any temperature influence

3/ What is the joint doing?

I am certain there will be other things but that's a starter for now.

Who wrote on the head the torque figure shown in the picture and why aren't you tightening to that?

desertfox

 

[hydtools]

Burndy terminal

http://www.drillspot.com/products/676846/burndy_ya31-2n_compression_terminal_cable_lug

Burndy recommended torque
See attached datasheet pdf file

Ted

 

[Guest102023]

More information needed. Torquing is never one-size-fits-all (if that is not mixing metaphors).

What is the coating on the part to be clamped? I am guessing it is a terminal lug, thus fairly critical.

 

[MiketheEngineer]

Call the mfg??

 

[cloonypan]

Hello,
I am the original poster. a electrical engineer.
My question is a about a electrical power cable terminal to be tighten on flat-shaped copper bus of a electrical panel. Per the panel install instructions, the M12 bolt tighten torque should be 44.1 Nm. However refer to other information on web, the torque of M12 bolt are recommended much higher than 44.1. Therefore I am curious why such big differences.
If the torque is not enough, the contact surface may result high contact resistance than cause over-heating.
Thanks your replies.

 

[Tmoose]

I have not researched your application but for a previous bus bar application I found that the recommeneded range of contact pressure for electrical contact ( copper, aluminum, other relatively weak materials) was pretty low compared to the structural joints I was used to dealing with.

 

[hydtools]

Did you not look at the Burndy, the manufacturer, information I posted above? Torque recommended would be adequate for electrical contact, not necessarily to structural capacity on the capscrew.

Ted

 

[drawoh]

Hello,
I am the original poster. a electrical engineer.

...

It helps us if you correctly classify yourself. Your profile says "structural", at least as of 2012/05/02.

If you look up torque for a screw or bolt, you get something based on the yield or proof stress of the screw or bolt. If we design something with the bolt in it, we may have to base our torque on the tapped hole, or on something that is being clamped.

I don't know my bolt markings very well, so I cannot tell what steel that bolt is made of. 44N.m is not that far out of line for grade[ ]5.8[ ]steel.

JHG

 

[desertfox]

Hi cloonypan

The reason that the torque on the internet is different to what you are seeing in the installation manual is probably because the torque specified is based on the strength of the bolt material which would be much greater than that of the copper or aluminium making up the electrical joint.
The torque specified in the installation manual should have been calculated by the manufacturer to prevent the material in the electrical joint from becoming overstressed after the bolt is tightened