Most of those sizes are pretty standard, in a 60 degree form, but several of the
taps are intriguing. The 12-20 is not quite 7/32-20. Depending on the thread
profile, it could be quite useful. The #16-20  would have been real handy on a
job I did back in about 2005. 8-40 shows up a lot in some older precision tools,
as well as in firearms.


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    On Saturday, January 25, 2020, 12:21:45 PM EST, Bill Ghio 
wrote:
 
 

> On Jan 23, 2020, at 10:56 PM, John Ruth  wrote:
> 
> Regarding Bill’s antique tap & die set, Erik wrote:
>> I would be unsurprised if there are some uncommon items in that set. I await
the details with great interest.
> 
> Hmm, Erik! You’ve given me something to think about.  ( I have an inexplicable
fascination with obsolete threads and threading systems. )

> SNIP

> So, the 1902 founding date for American Tap and Die brings them into the
United States Standard era, which yet mean that it could contain some that
aren’t National Standard or Unified National Standard.  Also, Tap & Die sets
tend to acquire “stowaway” passengers who weren’t in the original set!
> 
> ... (38 lines removed)>
16-20
12-20    AS
12-24    NC
12-24    NC
12-24    ASME    NC
10-32
10-32    NF
10-32    NF
8-40        NS    HSG11
8-40        NS    HSG11
5-40        NC
5-40        NC
5-40        NC