I hope you take this the same way as you hoped I’d take what you wrote and keep an open mind. I have become very thick skinned as I’ve heard your “arguments” more than once. Anyway, What would be the point of a discussion forum if all were in agreement?
I agree, I also like the discussion, it keeps our minds sharp.
If you find rounding off dimensions a difficult task, then serious problems must be almost insurmountable obstacles. When I'm figuring out when and what to round up or down, I always take the tolerance size into consideration. I'm often going from inches to metric and vice versa.
Sorry if I did not make myself clear here. I should have attached

to the statement. As for rounding direction, the resultant should never be beyond the thread tolerance which would always leave a finished thread which would gage correctly.
As you write,1/4"-20 UNC-2B has specified tolerances as per ANSI. Anything deviating from that is simply not to standard and must not be specified as such. If 1/4"-20 UNC requires a different pitch diameter than 2B then it must be specified and marked on the gauge and is certainly not 2B.
My original point here was that the different pitch diameter required in many cases is due to engineer error. The extra cost of special tooling could/should be avoided if the thread was correctly designated on the part drawing. The battle I am fighting is that too many engineers, or maybe their detailers, do not have the knowledge of the correct thread specifications nor do they go back to the standard to get the correct information. They just guess, or copy another drawing, or look in some inaccurate non-codified source. This lazy/uneducated approach causes problems for everyone using the drawing for the life of the drawing, which could be a hundred years.
That’s the advantage of measuring pitch diameter – you know where you are. As I also remarked, if a thread gauge is used, then the pitch and thread profile should also be OK.
I agree that measuring pitch diameter is a nice thing, but can not be the only check made of a thread. I did find your statement referenced above in your 21st August 2008, 03:44 AM post in the thread titled:
Measuring minor diameter of internal threads - How To?
My personal opinion on making the "perfect" thread is to use a combination of solid thread plug and/or ring gauge and pitch diameter measurement. A good thread is in the middle of the pitch diameter tolerance.
I can agree with this statement as a good way to measure a thread; however; it does require some skill on the part of an operator. This is why GO/NOGO thread gages are popular. Using GO/NOGO gages for checking of a manufactured thread is simple.
If only gauges are used to inspect a thread then a possible inspection has no way of knowing how much of the tolerance the machine actually requires and how reliable the process is – probably one of the major factors in quality control and assurance.
Again I agree. If you want to control the thread manufacturing process, additional measurements beyond using GO/NOGO gages are needed. With the tool you have designed, or tri-roll gages, measurements can be documented and SPC can be implemented. This process still does not require the rounding of the parameter values.
Working where you do, and with the products you have, may make you slightly biased

Maybe even a wee bit one-eyed.
I’ll leave “nano”-philosophy to the guys in the white coats and their cotton gloves in their temperature controlled environments.
In a "Calibration" related [forum], I'm probably with people who work in temperature controlled environments - my target "audience" is machinists and production technicians in general who measure machine produced components.
The people reading this forum for the most part are the white lab coat guys. What you are promoting, I believe, is still best implemented at the local level. I agree that it can be very useful in the machining process; however; if some one chooses to round, it needs to be their decision and their calculation so that they can defend it.
Publication of thread data should always be fully accurate. Any competent machinist looking at the accurate data would be able to do any rounding in his head. I still contend that publishing erroneous data only exacerbates the spread of bad information, and that creates problems which are far reaching.
In the countries using the metric system ... a standard 6 inch caliper is referred to as a 150 mm caliper. You must admit it would be daft to call a 6 inch caliper a 152.4 mm caliper or a 150 mm caliper for a 5.9055 inch caliper.
Sorry, this example does not hold. It is apples to oranges. Thread specifications are published on drawings, which are then taken as the final word, regardless of how erroneous they appear. No one would specify a 6" caliper on a drawing. And that is the point. I can foresee discussing a drawing with an erroneous thread specification and hearing the engineer’s defense as: “but I have this chart that I found on the internet.”
To me it's a question of knowing when to use common sense.
I agree with you so many times. This is another time.
I notice in ASME B1.1 a typical dimension is given as 0.003969" - when are dimensions to 6 decimals actually needed? I'm guessing it's only given that accurately so that it can be used for calculating purposes.
What you have said is correct. That is the precision that the B1 committee has gone to assure receptive accurate data whenever someone calculates the data.
Try going on to a shop floor and talk about dimensions and tolerances given to 6 decimal points. You'd get some very funny looks

in most places.
The person on the shop floor should not have to worry about the 6 decimal places. They have to look at the thread chart, or the drawing, or the thread engineering software, or the pitch diameters marked on the gage and work from there.
In summary, the tool you sell is useful if used in conjunction with, at a minimum, a GO gage, but the chart you have published is ripe for unintended abuse. If a chart is published that proposes to assist in calculating thread pitch diameters, regardless of the disclaimers printed on the chart, the data should give the most accurate data. Publishing thread pitch diameters that are “close enough” is just assisting the spread of error.
Whew! This much typing and thinking all in one day is too much like WORK.