Hardness in design?
Hardness in design?
(OP)
Hi all,
I'm an engineer fresh out of college and I'm doing some design work.
I need to figure out if the ABMA standard for locknuts is sufficient for my application of it or if I need a hardened nut.
The standard that this locknut is going by is that it has to have a tensile strength of atleast 25000PSI and Rockwell B hardness of 82.
In my application I will be tightening the nut down to 13.5 ft-lbs and applying a 1000 lb load to it.
I know that with the given tensile stress it should be able to handle about 3000 lbs of load (calculated from the futek bolt calculator). But what about the hardness? How will that affect the performance?
What I'm worried about is the threads in the nut deforming and eventually stripping from the ammount of load.
Thanks much!
I'm an engineer fresh out of college and I'm doing some design work.
I need to figure out if the ABMA standard for locknuts is sufficient for my application of it or if I need a hardened nut.
The standard that this locknut is going by is that it has to have a tensile strength of atleast 25000PSI and Rockwell B hardness of 82.
In my application I will be tightening the nut down to 13.5 ft-lbs and applying a 1000 lb load to it.
I know that with the given tensile stress it should be able to handle about 3000 lbs of load (calculated from the futek bolt calculator). But what about the hardness? How will that affect the performance?
What I'm worried about is the threads in the nut deforming and eventually stripping from the ammount of load.
Thanks much!





RE: Hardness in design?
If the nut is too hard, all the load will be carried by one thread, which will shear, and then the next thread will take up the load, etc, and the nut will strip by pulling a nice triangular wire out of it.
I swear that used to be in engineering textbooks.
Mike Halloran
Pembroke Pines, FL, USA
RE: Hardness in design?
Are there any equations or rules of thumb to go by in determining what hardness should be used with a certain load/application?
Thanks again.
RE: Hardness in design?
If you don't have experience with bolted joints, you can educate yourself with some of the free information on the Internet:
FAQ725-215: Where can I find info on fasteners on the Internet?
or from better sources:
FAQ725-600: What are good fastener references?
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Hardness in design?
RE: Hardness in design?
Typically for regular bearing types the bearing balls or races will complain long before the nut. A nice detail is to have a shaft shoulder positioned to handle the usual or heavier thrust load