Disassembly torque required for a torqued and glued bolt
Disassembly torque required for a torqued and glued bolt
(OP)
Hi everyone,
I have a question here concerning the interaction of different locking devices while used together in an assembly. For example, what would be the required torque to disassemble a bolt if it was torqued at assembly to a value of 500 lb-ft and if we added a threadlock glue (loctite) that requires a torque of 1000 lf-ft to disassemble, if used by itself. Does these two values add to make a total of 1500 lb-ft? Or does the larger value (here 1000lb-ft) rules the disassembly?
I need help to understand the behavior of this assembly. Thanks.
I have a question here concerning the interaction of different locking devices while used together in an assembly. For example, what would be the required torque to disassemble a bolt if it was torqued at assembly to a value of 500 lb-ft and if we added a threadlock glue (loctite) that requires a torque of 1000 lf-ft to disassemble, if used by itself. Does these two values add to make a total of 1500 lb-ft? Or does the larger value (here 1000lb-ft) rules the disassembly?
I need help to understand the behavior of this assembly. Thanks.





RE: Disassembly torque required for a torqued and glued bolt
This assumes that the Loctite didn't get on the faces.
RE: Disassembly torque required for a torqued and glued bolt
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Disassembly torque required for a torqued and glued bolt
So if I understand, there is no direct relation between the two locking methods (like 1+1=2). On the other hand, both locking methods must be overcome in order to disassemble the part, so that the overall torque required to disassemble the part will be over 1000 lb-ft. Is that right?
Similarly, if we torque a bolt to a certain amount of torque (500 lf-ft) and than drill a hole through the part and the bolt and than insert a pin to prevent rotation, would the same theory apply (if the torque required to shear the pin is 1000 lb-ft)?
RE: Disassembly torque required for a torqued and glued bolt
Had a case once where a big 2" dia. nut (thread size) kept working loose because of insufficient preload. The heavy nut would fall 30-40', and could've killed someone. Maintenance decided to fix it without telling us in engineering. They WELDED the far end of the nut to the threads after cutting the bolt off flush. Sure enough, the bolt broke via fatigue, and when it dropped it made a bigger dent in the floor because it weighed more with some of the bolt still inside! TWICE!
Also, in vibration service your preload MUST be higher than the service loads, or you can get fatigue cracking without any fretting-related loss of preload.