Thread callouts

Here is what the standard says.
.250 - 20UNC - 2B
First nominal diameter in decimal, then dash, then threads per inch/lead, then thread form and series, then dash, next class fit designation, then finally any qualifying information ex. MOL, SPL, LH.
This was pulled directly from the ASME code book.

My vote would be for #5-- if you want to specify a source other than Y14.6 to justify yourself, you could use Machinery's Handbook as an authority.
That said, I suspect that any of the 6 callouts would work just fine--is this really a battle that you need to fight?

Its just a symptom......
First its thread call-outs...... Then revision schema..... Followed by Title Blocks...... Summed up nicely by file naming conventions and classifications......
Using a known standard removes the "ego" from the equation. And for whatever reason there appears to be a fair amount of it in any company.
Eliminates the "this is the way its always been done around here" or the "I remember when...."
Don't know how many times I've heard managers ask if the PDM I use can control file names and locations (i.e. prevent somone from doing an end run and putting files on their local drive -- for archiving purposes of course!"
Been caught in his dilema more times than I want to remember.
Good luck.
Len
Michael wrote:

Steven,
I agree with SWX-VAR-JP, except I think the spaces are not needed. I don't have the official ASME Y14.5M-1994 standard, but I have a good reference book (which I recommend) called "Design Dimensioning and Tolerancing", by Bruce A. Wilson, which is based on the latest ASME standard. It says the minimum amount of information that must be given for a thread is the "nominal size, threads per inch, thread form, and thread class". It shows an example as ".750-10UNC-2B" for threads that go through a part, or if thread depth needs to be called out, such as for a blind tap, then the example is ".625-11UNC-3B (insert depth symbol).62", where the depth symbol is a "T" with an arrowhead pointing downward. Also, the book notes that nominal size for Unified National Course threads is equal to the maximum size limit of the major diameter on an external thread. Lastly, it notes that additional information can be found in ANSI Y14.6.
Hope this helps settle your differences, although I would stress that in my experience, most shops have a practicing set of standards that are "what the guys on the floor are used to", and the official standards don't always have to be followed to the "T", especially if drawings are for "in-house" purposes. I would choose my battles in deciding what is best for your place of work, and in some cases just go with the established precedent.
Cheers,
-JOSH