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galal_elden
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Join Date: Jan 2010
Location: pipe line project - KSA ( welding inspector - CSWIP 3.1)
Posts: 36

How many threads have to be appeared over the nut

06/03/2010 3:43 AM

Is there any code states about the number of thread over the nut ( for flanges with B.F valve), is it "D" of the bolt or 3 threads for all diameters.
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user-deleted-1105
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#1

Re: How many threads have to be appeared over the nut

06/03/2010 4:43 AM

We had this very question a few weeks ago, I think the conclusion was that there are recomendations or requirements from some customers but no actual standards.
from a mechanical point of view, as long as all the threads in the nut are engaged that's all that matters.
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rakesh_semwal
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#2

Re: How many threads have to be appeared over the nut

06/03/2010 9:58 AM

Half of the diameter of the bolt, Thats my common sense formula, Not a standard code.
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Gannet
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#3

Re: How many threads have to be appeared over the nut

06/03/2010 6:50 PM

In aircraft applications a minimum thread protrusion beyond the top of the nut in one complete thread beyond the lead in chamfer on the thread. If not, then the bolt should be replaced with a longer one. Also, we have a maximum of three thread protrusion. We actually have gages for measuring thread protrusion because of the quantity of fasteners involved.
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farmatt
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#4

Re: How many threads have to be appeared over the nut

06/03/2010 7:13 PM

It also depends on what type of nut you are using. Some types of lock nuts dont require any protrusion. When welding nuts to permanently fix them to bolts, (theft prevention) I leave the bolt slightly recessed so the weld is harder to grind off. Under some extreme circumstances when I have had no choice, I have even threaded a ny-lock nut on upside down because there was not enough bolt.

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farmatt
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#5

Re: How many threads have to be appeared over the nut

06/03/2010 7:16 PM

As to the code on flange bolts, I am not totally sure but a millwright I once worked for would require bolt protrusion equal to the diameter of the bolt.

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Padmanabhan Iyer
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#6

Re: How many threads have to be appeared over the nut

06/04/2010 4:53 AM

3 threads to b visible out side as a gud engineering practice.
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farmatt (2); Gannet (1); Padmanabhan Iyer (1); rakesh_semwal (1); user-deleted-1105 (1)

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