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265716 Erik Levin 2018‑04‑14 Re: Brown and Sharpe 870 (circa 1905 to WW-I)
Troy Livingston offered: 


>As a fellow hoarder of odd things thready, I checked my out of date tap
>and die list and found taps but no dies of the correct size. However I
 
>recently pick up a stash of such things and in a proper Galootish time
 
>frame have dug through and found a single 8-40 die. If you haven't given
>up and made one already I would be happy to put some threads on a bit of 
>steel rod and send it your way. Then all you would have to do is fit the
 
>knurled knob.


I never followed up on this thread as weather, work, and life have been keeping
me occupied for the last several weeks.


I got some input off list with a few leads, and went through the early B&S
catalogs, Machinery's 5th edition, a few other early handbooks-- I don't have a
world class collection, but I did load test the book case to 150lb/running foot
when I built it-- I found a best match that is odd, but plausible: Not #8-40,
unfortunately. I found a screw in another tool, tested it, and no go. The size
was more of a 7.6-40. I got really good measurements by heat softening a
dinosaur-based polymer and using the hole as a mold.

The thread seems to be a Cycle Engineers thread-- CEI, the original, pre-
adoption as a british standard, which is BSC and is different. I have not found
consistent information as to when the changes occurred, and the names seem to be
used inconsistently on the web, so I went with the numbers in Machinery's 5th
edition (P1027, pub 1914) and the best fit of 0.154-40.


No die being available, I single pointed the thread on a piece of rod and press
fit a knurled bronze head that looks a good match but will never be mistaken for
original.



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