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Join Date: Jan 2010
Posts: 3

BSW Instead of UNC

07/27/2017 4:19 AM

CAN WE USE BSW INSTEAT OF UNC STUDS IN SIGHT GLASS IN U STAMP VESSEL ... IF YES THEN DO WE NEED TO SUBMITT CALCULATION FOR SAME... IF ANYBODY HAVE BSW ROOT AREA PLEASE SHARE ITS 1/2" BSW

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#1

Re: BSW INSTEAD OF UNC

07/27/2017 4:26 AM

Please stop SHOUTING!

The only individual who can answer this is the one that signed the approvals box on the "for construction" drawing. The name of that individual cannot be seen from here, as the "for construction" drawing cannot be seen from here either.

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Anonymous Poster #1
#2

Re: BSW INSTEAD OF UNC

07/27/2017 4:34 AM

Sure. Go ahead. But if it goes wrong it's your fault. OK?

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#3

Re: BSW INSTEAD OF UNC

07/27/2017 4:51 AM

Do you mean the studs go into threaded holes? If so, no. 1/2" UNC has 13 TPI, BSW has 12. If you have bolts and nuts I'd be surprised if BSW is a problem, but it might be worth rechecking the calcs. Whether or not you need to submit them to somebody depends on your contract and where you are in the world.

I'm surprised that you can source BSW more readily than UNC, you might consider M12, possibly easier to obtain.

Anyway, stress areas, in2 on my data are

BSW 0.1385

UNC 0.1438

M12 0.1307

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Guru

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#4

Re: BSW Instead of UNC

07/27/2017 8:31 PM

Most BSW bolts (55deg) will fit into a UNC (60deg) tapped hole, with the exception of 1/2". You can readily get a thread chart via Google.

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#5

Re: BSW Instead of UNC

07/28/2017 6:06 AM

Both of these thread types are use for imperial thread.
BSF and BSW are Britisch measurement systems, while UNF and UNC are American measurement systems.
BSF and UNF are the fine thread systems, while BSW and UNC are the coarse thread systems.

The difference between BSF/BSW and UNF/UNC is dual:

  • The thread angle
    The BSF/BSW have a thread angle of 55° BSF-BSW thread angle The UNF/UNC have a thread angle of 60° UNF-UNC thread angle
  • The thread profile
    The BSF/BSW have a wave like thread profile. BSF-BSW thread profile The UNF/UNC have theorically a flattend crest and root in the thread profile, however to aid the manufacturing proces they are slightly rounded inside a maximum outline. UNF-UNC theoretical thread profile UNF-UNC practical thread profile

Be aware that although they look similar, they should not be used as full replacements or be mixed with each other!

  • UNF and BSF have completly different thread per inch value. So they don't fit.
  • UNC and BSW have the same thread per inch value, accept for the 1/2" size. Theoretical it would be possible to interchange them as they have the same amount of threads per inch. However due to the difference in thread angle, the connection would not be as strong as when using the proper combinations.
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Anonymous Poster #1
#6
In reply to #5

Re: BSW Instead of UNC

07/28/2017 7:53 AM

accept except

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Associate

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#7

Re: BSW Instead of UNC

08/01/2017 9:54 AM

As you refer to a "Sight Glass" in a Vessel I am assuming that you are working in a area where some kind of plumbing is being used ( ship, boat, chemical / oil plant) hence your use of British Standard Whitworth threads. This area is about the only one left where the Whitworth thread pattern is still used as a standard.

Depending if the product you wish to secure is covered by some form of Safety practice or regulations, I would think you would need to submit a Load Calculation if you are changind an existing specification shown on a drawing or other official document (Pressure test etc).

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