Increasing thread length
Increasing thread length
(OP)
I have a quick question about threads. I am trying to design a part with a threaded connection and it needs to be able to handle up to 1800 ft*lbf of torque. After doing this, I am only getting around 1200 ft*lbf. Would increasing my thread length help me reach the 1800 ft*lbf that I am trying to design for. I cannot change the size of the threads.





RE: Increasing thread length
Chris, CSWA
SolidWorks '15
SolidWorks Legion
RE: Increasing thread length
(Or if you don't like PDF https://www.fastenal.com/en/78/screw-thread-design.)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Increasing thread length
Consider thread form for instance, I suggest you research terms such as "buttress thread"; "square thread" and "trapezoidal thread".
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Increasing thread length
RE: Increasing thread length
We need a lot more information like the size/grade of fastener and the materials clamped in the joint that are being used,a bit more information about the application.
Also what is happening to the joint at at 1200lbsft? Are the threads failing?
If the joint is failing then you would be better off changing the materials either the fastener or the materials within the joint,depending on which as failed.
In theory increasing the thread engagement would increase the torque that the joint could withstand however that's only true if you assume that each thread takes an equal share of the load, in practice once the thread engagement as reached about 1.5 to 2 times the bolt diameter there is little to be gained after that.
Another way to increase the joint strength might be to fit a helicoil insert but this would only work if it's the female thread that's failing.
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: Increasing thread length
Just FYI looks like the OP has been edited but the original version indicated the OP might be a student. It's an interesting enough question that I asked site mgmt to give some leeway but we should probably try to phrase our responses in a way that gets the OP to do some digging on theory etc. them self.
(Note, just my 2C doesn't reflect site management opinion or policy etc.)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Increasing thread length
RE: Increasing thread length
Have you got a diagram of your system? All sorts of things could be generating torque. We have no idea of what you are doing.
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JHG