Equivalent US thread size somewhere between M4 and M5

oGaryo

oGaryo

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Hi I need to get hold of 2 x 316 stainless domed nuts somewhere between M4 and M5 size but US imperial thread.. Would anyone know what that thread size might be please?
 
I think 4BA is very similar in pitch to M4 Quite a lot of small (under 6mm) non-metric threads are from the "BA" series. Does it look like a coarse or fine pitch? Can you use a pair of verniers to measure (say) the length of ten threads and divide by ten? That'll give a pretty good idea of the pitch.
 
There is a very easy way to check if a small thread is BA or UNC, UNF or Metric. Just look at the bolt with a magifying glass. Metric and American threads are cut at a 60 degree included angle, but BA is 47.5 degrees, much sharper in appearance and easily told apart from the others. The only other types you might encounter are old British Whitworth, BSF and Cycle threads, all of which are 55 degree included angle, and so quite close to the SAE sises, some with the same pitch, and although not ideal the nuts can be interchanged on some sizes. e.g. quarter inch BSW and UNC are both 20 TPI.
 
American SAE sizes are quite logical from quarter inch up, for example quarter UNC is 1/4 inch nominal diameter by 20 TPI.

Below quarter inch they are numbered 10-32 etc. The first number relates to diameter and the second is TPI. The chart here explains it all.
 
Norman_E said:
There is a very easy way to check if a small thread is BA or UNC, UNF or Metric. Just look at the bolt with a magifying glass. Metric and American threads are cut at a 60 degree included angle, but BA is 47.5 degrees, much sharper in appearance and easily told apart from the others. The only other types you might encounter are old British Whitworth, BSF and Cycle threads, all of which are 55 degree included angle, and so quite close to the SAE sises, some with the same pitch, and although not ideal the nuts can be interchanged on some sizes. e.g. quarter inch BSW and UNC are both 20 TPI.
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While agree with that, take care... the tpi may be the same, but as has been pointed out, the thread cuts are different, so the security of the nut is not as good as when the correct one is used... of particular concern when mating BSP with NTP, where pressure integrity may be lost.

Far better IMHO to get the right nut/thread.... they're readily available!
 
TQA said:
Only if it is a non stressed non critical application PLEASE!

The thread strength will be dramatically reduced.

Better to get a set of thread guages, identify the thread, get the right nuts AND DO A PROPER JOB!
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Really ! A 4-5 mm thread is hardly lightly to be structural.....
 
davidej said:
Is the first number AWG?

It doesn't seem to say on the chart.
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I don't think so as AWG generally refers to electrical conductors and 12 AWG is 0.0808 inches whereas a a 12 thread size is more than double that at 0.1889 inches, just over 3/16 inch in coarse thread and slightly more in fine thread.

I find the small SAE threads a bit illogical as the overall diameters are not perfect fractions of an inch and even vary according to pitch.
 
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SpottyDog5 said:
Really ! A 4-5 mm thread is hardly lightly to be structural.....
Click to expand...
Lots of things will be held by M5 bolts... such as deck organisers, clutches, smaller winches and stanchions on boats below 35`

Wouldnt want to be near when one of them detatched itself from the deck as the thread parts from the nut when under the load of for example a 3rd reefing line in a gale,
 
Phoenix of Hamble said:
Lots of things will be held by M5 bolts... such as deck organisers, clutches, smaller winches and stanchions on boats below 35`

Wouldnt want to be near when one of them detatched itself from the deck as the thread parts from the nut when under the load of for example a 3rd reefing line in a gale,
Click to expand...

Not too many of them of a 25ft Rinker mobo :)
Running a die down to create a tread is not a bodge job, of course consider the application .
 
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SpottyDog5 said:
Not too many of them of a 28ft Rinker mobo :)
Running a die down to create a tread is not a bodge job, of course consider the application .
Click to expand...

Whilst cutting a thread with a die is standard paractice to make one offs, almost all small bolts have rolled threads, for good reason. A rolled thread is considerably stronger in the small sizes, as the rolling process does not leave any torn metal surfaces to act as stress raisers. Re-cutting one thread with a different one in order to make a nut fit is bad practice and although acceptable for lightly stresses fittings it is a practice best avoided, and the correct nuts purchased..
 
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Mearly offering a solution that may have helped in the absence of the "correct" domed nuts.
Gary is no fool, he will evaluate the suitability of the solution.
He hasn't stated what the application is, for all we know it could be holding the handle on the kettle :)
 
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