John wrote:

> Thanks for “the word” on M-F screw thread profiles.
>
> Your “Bamboo Trick” will become part of the “toolkit” for identifying internal
threads.
>


I don't know if this was true for all MF planes, but they were well established
in other fields that followed standards when they got into planes in the 1930's.
The wood impressioning trick has been seen here before from a number of people
(George first, many years ago?) I have another tool that I can use to directly
measure the pitch of small threads- an L-shaped length of rod  with 60deg
conical end on the short leg. I use this with the comparator stage by clamping
it to a magnetic base. I have actually made a few, but at the moment can only
find one. They are small and get lost.


The thread profile is as perfect a match on all the fixins' I checked as you
will find to the US standard 60 degree profile overlay at 20X.


Claudio wrote:


> Number 12 vs 1/4" confusion also


#14 is the worst, as it was 20 thread/inch. One of the shops I used to work in
had a lot of early 20th cty machinery and equipment, and one of our machinists
refused to believe there ever was a #14, despite all evidence including the
documentation for some of hte equipment. He would swear that it was a misprint
and tap 'em all out to 1/4"-20. Amazing how many failures followed this. I have
stories that will remain untold to avoid embarrassing the guilty, including me.





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many no-longer-standard taps and dies. 1/16"-64, anyone?