Raimy;
A long time ago one cold winter afternoon I decided it would be more interesting than watching the idiot tube & I sat down with a programable calculator & played with the gauge vs dia chart from the Britisf proof house, which went down to the 172.28ga @ .300". I also have an early German chart which gives the same figures. I found that for every gauge to "Round" to the nearest 3 decimal place found on the chart it was necessary to carry the 1 ga to 6 places. Going to 5 places 1.66928 is too small & 1.66929 is too large. 1.669285 if cubed, divided by the gauge number then the cube root taken (your formula) will round to the 3 place dimension of every gauge on the chart from 1 to 172.28. Any other gauge can of course be determined by the same formula, which is how I derived at .295" for 181 & .266" for 248. I now have a calculator with 1.669285^3 (4.65148337) stored in memory on the desk by my computer. All I now have to do is pick it up & turn it on, hit MR, divide by a gauge # & take the 3√ & have the dia. To find the gauge of a given Dia I simply hit MR & ÷ D^3.
If you just take any one dia off the chart some others may be in error by as much as a "Whole .001") due to rounding error. Big deal I know, but it was more fun than watching some stupid TV show.
