Obviously the steps (or similar) that were taken when the dimensions were converted in the past. Can't say whether they used 25.4 or some other inch definition from the time.
The point is that with the record dimensions what they are, it shows that they were converted and rounded to the nearest fractional size within acceptable tolerances. They were never made to match the name they were called? The only problem with 32-nds though is they are not found on standard fractional inch based rulers and thus it may be difficult to measure in 32-nds. I've seen some rulers that have 32-nds, but with the lines so close and cluttered, you have to have super human vision not to be off a mark or two. If you lived in the 1920s (or earlier) , then you would have had to use tables and slide rules. Wouldn't that have been fun? Metrication would be a lot simpler if some engineers in the US really understood significant figures and tolerances and would do the inverse of what the record industry did. Simply convert the dimension to millimeters using the 25.4 factor then round to the nearest whole millimeter. Then factor in the original tolerances and see if the nearest whole millimeter does fall within those tolerances. If it does, then make that the new number and adjust the metric tolerances to suit. If not, then go to the nearest 0.5 mm and try again. The idea is to have as few digits to the right of the decimal point as possible. Jerry ________________________________ From: John M. Steele <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Sunday, April 5, 2009 11:01:26 AM Subject: [USMA:44385] RE: Records Mathematically: 1) Convert to decimal inches, by dividing by 25.4 mm/in 2) Record and subtract the integer inches to deal with only the decimal. 3) Multiply by the largest denominator I am willing to entertain (8, 16, 32, etc) 4) Mentally round to closest integer If I get a result that is even, I can simplify the fraction. If I feel the number is too far from an integer, I can go to the next denominator choice in step three by multiplying by 2 again (and I can repeat until I am satisfied, but I have to remember what I am doing to the denominator). When I am satisfied with the vulgar fraction, I can check my work by computing decimal inches, then millimeters. I'd hate to do it with a table of logarithms, but with a calculator, it is not bad. --- On Sun, 4/5/09, Jeremiah MacGregor <[email protected]> wrote: From: Jeremiah MacGregor <[email protected]> Subject: Re: [USMA:44375] RE: Records To: "John M. Steele" <[email protected]>, "U.S. Metric Association" <[email protected]> Date: Sunday, April 5, 2009, 10:52 AM How does one accurately express a rounded millimeter value in a vulgar inch fraction and stick to either 8-ths, 16-ths or 32-nds? For example, if you were an engineer in the 1920s and had to convert a European metric spec for American use, how would you do it and still retain the same original dimensions in the converted value? Jerry ________________________________ From: John M. Steele <[email protected]> To: U.S. Metric Association <[email protected]>; [email protected] Sent: Sunday, April 5, 2009 10:34:35 AM Subject: Re: [USMA:44375] RE: Records Your dimension of 302 mm is correct, more correct than the nominal 12". However, Steve's assertion that it is inch based is also correct, as written in the specification. Since the International size is claimed to be 300 mm, and 302 mm differs from it by a few multiples of the tolerance, as an engineer, I have to say they were engineered to be different sizes, even if they are "close." Assuming the International size has a similar tolerance, they will not overlap. --- On Sun, 4/5/09, Jeremiah MacGregor <[email protected]> wrote: From: Jeremiah MacGregor <[email protected]> Subject: [USMA:44375] RE: Records To: "U.S. Metric Association" <[email protected]> Date: Sunday, April 5, 2009, 9:59 AM John, Thanks for verifying what I have said. We now have proof that I am correct and Stephen is wrong. But I highly doubt Stephen will change his position and continue to spout error. The RIAA spec is very interesting as it butts up against an interesting problem in converting millimeter dimensions to fractional inches. I would say that in 1963 when the spec was made (possible from an older spec) that decimal inches were rare and not popular and it was common to express all (or most) inches in fractions. So, how do you convert a rounded metric number to a fractional inch and then come up with a usable fractional size that is in either 16-ths or 32-nds? Anything smaller is not practical. 302 mm converts to 11.89 inches. The nearest fraction is 11.875 mm which is 11-7/8 inches. This however is only 301.625 mm. The reason for the asymmetrical tolerances is to accommodate rounded numbers in both units, the 302 mm in metric and the 11-7/8 in inches. If we add the 1/32 tolerance to 301.625 mm we get 302.42 mm. The average of the two is the 302.02 mm you noted, which for all practical purposes is the 302 mm intended. However, in inches there is no common fraction to equate to 302.02 mm. So the closest common fraction was chosen and the tolerance was made asymmetrical. If the RIAA spec were ever to be updated it could simply drop the 0.02 mm extra you noted and simply make it 302 mm +/- 0.4 mm. Would you agree? I do find it interesting that the RIAA wanted their records to be an extra millimeter in radius bigger then the standard 300 mm. Could be they wanted to have extra leader space at the beginning. As a side note I wonder if the 1963 spec was an update to an earlie spec and how far back the spec really goes? If so, and the inches were in fact not post 1960 inches, then how would pre-1960 inches or even pre-1900 inches affect the outcome of the conversions? At least we now know that the dimensions are what is intended and that the reference to shrinkage is just wishful thinking. It just goes to show that the extremist propaganda that claims everything in the past started out as inch based is wrong and that there are many examples that actually started out as metric based and were later corrupted by the English world in inches and the metric history was forgotten. It is time to revive the truth about products that originally were metric to begin with. Jerry ________________________________
