Threads

[mgrenier1]

I need to add some threads to Inventor's thread.xls file and I'm wondering something, it's not really a question about Inventor but I'm not sure where to ask it.

What makes a thread UN-UNC-UNF-UNEF-UNS? I get that a UNF thread will have more TPI than a UNC one of the same diameter but where to draw the line between the two?

Every chart I found online stops at 4 inches and so does the one in the machinery handbook

Wikipedia doesn't really help much

I found a calculator on Engineer's Edge but it lets me choose the thread designation no matter how much TPI the thread has.

I need to add 7 1/4'' and 7 1/2'' to the file and I cannot find out if it's UNF, UNC, UN or UNS.

Hope I make sense.

[swalton]

I suspect that you will need to get a copy of ANSI/ASME B1.1 which defines the UN, UNC, UNF, UNS series threads.

A source is:

https://www.asme.org/codes-standards/find-codes-standards/b1-1-unified-inch-screw-threads-un-unr-thr...

My guess is that 7 1/4" and 7 1/2" threads will be one of the constant pitch UN series threads.  Maybe the 4 or 6 TPI families. 

If the ANSI standard does not go as large as the threads you want, I guess you get to design your own thread form.

[NigelHay · Accepted solution]

There's a PDF version here https://pppars.com/wp-content/uploads/2021/08/ASME-B1.1-2019.pdf

As Swalton says, the larger sizes seem to be in the constant pitch series.

[mgrenier1]

Thank you very much