Help identifying a thread type?

[Sawdust=manglitter]

Could someone please help...

I’ve been brought up on metric threads, so dont have much experience with the various alternative imperial thread types.

I need to get a nut for a bolt which has a thread pitch of 16tpi with an outer diameter of 12.5mm and a shaft of diameter of 11.0mm. I’ve looked at various charts of thread types on the web and cant find anything close to these dimensions, so if anyone can help then it would be greatly appreciated

 

[ovenpaa]

1/2" UN maybe?

UN imperial screw thread calculator may be of use.

 

[LJM]

1/2” bsf, I think

 

[shed9]

I suspect the 1/2" BSF is the likely culprit. You could always pop into a local fasteners supplier and get them to check and supply the appropriate nut at the same time.

 

[Sawdust=manglitter]

Thanks all for the suggestion!

 

[J-G]

12.5mm is just shy of ½" (12.7mm) and within the normal tolerance that one would expect - even for a pristine thread.

At 16 tpi it falls exactly into the BSF standard - Whitworth form, fine pitch series. UNF would be 20 tpi but the left-pondians are happy to call any dia. pitch combination a 'standard'

The 11.0mm 'shaft dia.' is probably irrelevant but the root dia. of ½" BSF would be 0.42" = 10.668mm so it is possible that the 'shaft' has been machined down to that (close enough) -- and a nut would normally have a core dia. of 11.1mm so should become 'free' once past the thread on the bolt, potentially making the bolt semi-captive.

 

[sploo]

1/2" and 16tpi? Definitely 1/2" BSF (Metric, Metric Fine, BSW, BSF, UNC, UNF and BA Thread Dimensions). The one that tends to get me is 1/2" BSW (12 tpi) vs 1/2" UNC (13 tpi); just close enough that you have to be very careful!