UNEF Threading Above 1-11/16"?

[Packermanfan]

Hi all,

We are having quality problems regarding 2" OD male threading. We get a "pass" result with our no-go gauge (not even a full turn on), but the customer is getting a "fail" when using their gauge. However, they specifically stated their gauge is from "G4988 2-16UNEF-2A Thread Plug set". As far as I know after every Google search I could think of, UNEF stops at 1-11/16" diameter, beyond that there is only UNC coarse threading. Does anyone know how or why they would have a gauge labeled as such? Is it a typo or is there some extended standard I'm unaware of?

 

[3DDave]

Sometimes the thread specs have an underlying formula to determine allowable clearances that can be extended beyond the typical uses.

See

https://www.machiningdoctor.com/cha...rts/#limits-of-thread-dimensions-unc-unf-unef

for what are likely to be the formulas (the real reference is ASTM B1.1)

 

[hydtools]

Packermanfan, your go gauge should go the length of the complete thread to pass. I'd call less than a full thread a fail.

Ted

 

[Brian Malone]

hydtools - I am interpreting the OP post as their "no go" gauge does not thread on past a partial turn thus indicating the thread they are cutting passes the no go condition of not accepting the no go gauge, while the customer's no go gauge is threading on multiple turns thus indicating the male thread is undersized, thus a fail condition.

Packermanfan - have you had your gauge and their gauge inspected by an independent metrology lab? I kind of missed your question on the UNEF designation - I don't work with large threads commonly so I had to do some searching, too - I only see 2-16 UN threads listed. Possibly, your customer has put in a typo?

 

[Brian Malone]

Parkerman -

I just found this link for thread forms specifically using 16 threads per inch. It is a UN extra fine thread series for special applications.

https://www.gewinde-normen.de/en/16-un-thread.html

Maybe this is the basis for your customer's gauge?