On 2008-10-13, Phil Kangas wrote:

[ ... ]

So what I'm reading is the information given on this gauge is pretty
much a waste of time. Why give double depth of thread when the compound
rest only affects the radius.

a) *Some* compound feed dials read in diameter, not radius.

b) Way back when (when the thread gauge was designed) lathes
did not always have a compound anyway.

It would be far more handy if that chart
gave the actual compound rest movement required for a given thread.

At what compound angle? Even just sticking with 60 degree
threads (since this is a 60 degree center gauge, not a 55 degree for
Whitworth threads, or a 28 degree for Acme threads)? It is common to set
the compound at 29 degrees or 29.5 degrees (both a little below half the
thread angle) -- and each of those requires a slight adjustment of the
compound infeed.

And
the four most common threads (14, 20, 24, 32) ?

Back when it was designed those probably were the most common
thread pitches.

Thread pitch gauges are
far more useful than the scales given.

Certainly -- but not everyone has thread pitch gauges in an
early shop -- but everyone was expected to have the center gauge.

Enjoy,
DoN.

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