[Shop-talk] Weird machine screw

[Randall]

> Is the Whitworth size just really close to the UNC size, and 
> we can get away with the mismatch?

In this case, yes.  Many (but not all) of the BSW sizes are the same thread
pitch as UNC and usually (tho again not always) there is enough slop to
allow the two to mix in spite of the slight differences in thread profile.
For threads as small as 1/4-20, I find it hard to see the difference even
with a thread gauge and a jeweler's loupe.

-- Randall