Error of rounding basic dimension 2

[SeasonLee]

Please ref to “NASA Engineering Drawing Standards Manual” (you may download it from here

http://mscweb.gsfc.nasa.gov/543web/files/GSFC-X-673-64-1F.pdf).

Page 90 last paragraph b. Rounding Basic Dimensions.

To convert basic dimensions of drawings from inches to millimeters, the converted value shall be rounded to three decimal places since this shall provide a maximum conversion error of 0.00002 inch.

I am interested to know where this figure 0.00002” comes from. Thanks for your help.

Season

 

[CheckerHater]

It's 0.001mm divided by 25.4 and then divided by half

 

[SeasonLee]

Thanks CH, divided by 2, why.

Season

 

[cowski]

When you round to the nearest .001mm, the most you will "lose" due to the rounding process is .0005mm.

www.nxjournaling.com

 

[CheckerHater]

So, it's divided by 2 first and then divided by 25.4

 

[dgallup]

Division is an associative operation, the order is unimportant.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[CheckerHater]

It's not the order of mathematical operations, it's the order of logical steps:
First we come to realization that "When you round to the nearest .001mm, the most you will "lose" due to the rounding process is .0005mm."
Then we convert 0.0005 mm to inches by dividing by 25.4.
Then we attach smiley face to it as a warning that the whole statement shouldn't be taken very seriously.