Actually your 39.37 meter to inches figure is the approximation. It's
closer to 39.3700787402. 1 inch = 0.0254 meters is exact.
John KK9A
Richard Karlquist N6RK wrote:
I have had a pet theory about off shore threads, may or may not be
valid:
If a manufacturer in Asia has screw machines calibrated in metric
threads,
there is a double dilemma: metric threads are given in mm per thread
while imperial threads are given in threads per inch. Thus there is a
reciprocal relationship in addition to the factor of 2.54. Along with
this,
there is the problem that any errors accumulate and get worse with more
turns of engagement. Also, the factor of 2.54 mm/inch is only an
approximation. The official conversion is that there are exactly 39.37
inches in a meter. This translates to 2.540005 mm/inch. I don't know
if that is part of the problem.
I could quite possibly imagine a case where Chinese SO-239 threads fit
Chinese PL-259 threads perfectly if they were made on the same screw
machine, but would not mate with Amphenol parts.
---
Rick Karlquist
N6RK
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