Rules For Rounding Decimals
Rules For Rounding Decimals
(OP)
I have searched for rules of rounding and no luck. ANSI Z210.1 and ANSI/IEEE 268. Anyone have an idea where I might find a standard pertaining to rounding, that will satisfy ASME Y14.5 or Y14.41?





RE: Rules For Rounding Decimals
Regards,
Cory
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RE: Rules For Rounding Decimals
KENAT, probably the least qualified checker you'll ever meet...
RE: Rules For Rounding Decimals
And no, I DO NOT propose using fractional equivalents on a NEW design unless driven by tool sizes or such.
The real problem occurs when the digit following the last place to be rounded to is 5. For example .625 rounded to 2 places. Do we make it .62 or .63? At one time there was a rule which apparently is no longer existant.
RE: Rules For Rounding Decimals
There are standards regarding this kind of rounding in the Statistics principle, but I do not know what the stadards are. Though, I do not believe they are applicable to engineering drawings since (from what I understand of them) they make some assumptions that may contradict ASME Y14.5M's rule regarding the absolute nature of dimensional tolerancing.
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Rules For Rounding Decimals
KENAT, probably the least qualified checker you'll ever meet...
RE: Rules For Rounding Decimals
KENAT, probably the least qualified checker you'll ever meet...
RE: Rules For Rounding Decimals
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Rules For Rounding Decimals
RE: Rules For Rounding Decimals
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Rules For Rounding Decimals
I learnt it the way you did, and the ASTM standard says...A QC type a long while back, whose opinion I trust, noted that rounding up the 5 creates a statistical bias in the data, slight but measureable. Rounding only to the even number (i.e. rounding down on the odd numbers) means that half the time you round the 5 up, half the time down, resulting in no bias or at least a more randomized bias. Made sense to me at the time, and have used the technique ever since. Glad CoryPad could point us to the reference, a star for him on that.
RE: Rules For Rounding Decimals
Please see pg.101, 10.2.2.2.
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Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
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RE: Rules For Rounding Decimals
RE: Rules For Rounding Decimals
I accept whatever my CAD software does. Anything else would be a lot of work.
Presumably, I am rounding .625 off to .62 or .63 because I do not need the accuracy. If I actually cared about this, I would specify the extra decimals.
JHG
RE: Rules For Rounding Decimals
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Rules For Rounding Decimals
RE: Rules For Rounding Decimals
Also, if I put .63 on my drawing, I like to model .6300000..., not model .625 and 'round' to .63 at the drawing, again I've seen accumulations of this kind of thing cause issues.
KENAT, probably the least qualified checker you'll ever meet...
RE: Rules For Rounding Decimals
One of the nice things about GD&T position and profile tolerances is that you do not need to round off. You can apply a dimension of .625", and a position or profile tolerance of .05". The drawing correctly shows your model, and it shows the accuracy you want.
Basically, if I apply a dimension of .62"±.05", an error of .005" is irrelevant. I would be tempted to round the model and dimension off to .60".
JHG
RE: Rules For Rounding Decimals
Frankly .625 ±.050 is a gross example that we seldom find.
When you are dealing in 3, 4, and even 5 place tolerances which I know KENAT does as well as I in my job, sloppy rounding, (often the result of bad modeling) becomes a real problem.
RE: Rules For Rounding Decimals
KENAT, probably the least qualified checker you'll ever meet...
RE: Rules For Rounding Decimals
I think it is in compliance with the old version of ANSI Z210.1
Thanks for all the input.
RE: Rules For Rounding Decimals
It has good info.
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion