screw length in connection with clamping screw

[999]

Hello.
I wanted to know if there was a rule in general to determine the screw length in a connection with the clamping screw, i.e. the minimum length of the screw part that must "take" on the screw. provided that depends on many factors such as the materials of the pieces to be connected as they explained to me, according to the information that provided me the teacher should be between 0.8d and 1d (nominal diameter) that sincerely in some cases seems to me a too low value. I found nothing on the text about it and seeing a little around I found a generic value of 1.5d.

 

[tortellino]

Then:
the screw thread is considered as a beam: a curved beam, but still a beam. a free framed beam, to be precise.
the load acting on the beam is equal to the force with which the screw is tightened.
Now: this force exercises a moment inflating the beam: you know the length of the beam that is (average diameter -hazel diameter)/2.

multiply the force applied to the arm I told you and find the moment flenching to the socket. By the way: this force is applied on the average thread diamer.
then:
mf/wf= admissible sigma.

wf revenues (which then is the bending resistance module of a rectangle whose height is given by the thread geometry to the attack with the hazel) and known that you get the length of the curved beam.

2* lazy * hazelnut diameter * thread number= length

revenues the number of threads, add a couple for safety and deliver the task.

I hope I've been quite clear, given the time.

 

[999]

absolutely clear, indeed thanks to the answer also in virtue of the late hour.
the subject is "assisted drawing by computer" and we say that at the moment they gave us more than any of the guidelines to correctly represent the connections through autocad, omitting many of the information you provided to me, and that I hope will be given in the university process by means of more specific subjects.
anyway thanks again.

 

[meccanicamg]

If you do a search in the forum you find my demonstration and my mating length formula according to the screw breaking loads and mothervite.