rounding off to 10mm

[Walterke]

Is there a way to round off numbers to the nearest 10mm?
As in 2776mm becomes 2780mm.

Second: while searching this forum for an answer to this, I found this (from 2007):

When rounding, examine the figure following (i.e., to the right of) the figure that is to be last. This figure you are examining is the first figure to be dropped.

If it is less than 5, drop it and all the figures to the right of it.
If it is more than 5, increase by 1 the number to be rounded, that is, the preceeding figure.
If it is 5, round the number so that it will be EVEN.

The thread in question, however, does not make a reference to any standard on this. I'm interested to know if this is the same way for ISO.

Thanks.

NX 7.5
Teamcenter 8

 

[pmarc]

CH,

"As long as you stick to same rules you get same results"

Wasn't it the reason why Walterke actually asked the question? Didn't he ask for the standard in order to see if there is an official ISO document forcing everyone to stick to the same rules while rounding off, always (at least in ISO world)?

And referring to your latest example - please look to the link.

http://www.hartnell.cc.ca.us/faculty/shovde/chem22s/roundingrules.htm

If you follow the rules from it you will not always get the same results like you are saying (example with .375). But even knowing this, the method from the link itself is not the key here. The key is that there are different round off methods, so different final results may occur due to that. Which one is correct and which is not is the other side of the story.

 

[CheckerHater]

Dear pmarc,
Can you please reference the standard that says this particular rule applies to how we round dimensions?
And when it comes to different ways to do the same thing; I suggest you research “Indiana Pi Bill”. Just because something was approved unanimously, doesn’t always make it right

 

[pmarc]

Dear CH,
Can you please reference the standard that says "your" rule applies to how we round dimensions?...

...I will repeat, there are different rules because there seems to be no standard clearly saying how to round off and in consequence making other rules illegal or at least not preferred in certain applications (i.e. technical drawings).

Please don't get me wrong. For your example I would round off in exactly the same way like you did, but not because of a standard, but because we were obviously taught the same during math classes. However even then I wouldn't say for sure that our standpoint was the only one absolutely correct. I am far from relying on wikipedia, but when you look to the following link you will easily see how many different rounding methods exist:

http://en.wikipedia.org/wiki/Rounding

I used the previous link just to show you that even for such a fundamental thing (I will never ever say "simple") someone may use different approach to ours and the final result of rounding operation will be different. And it is interesting that I found at least couple of websites supporting this method. All were not referring to any standard. It is even more interesting that the webistes standing behind our method did not mention anything about the standard too.

 

[CheckerHater]

Pmarc,

I agree. Do you think it deserves further investigation? The standards mentioned in connection to rounding problem are numerous, but none of them actually addresses the issue directly.

Some examples are:
ASTM E 29 - 06 Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications – operative words “test data”, not exactly drawings.
IEEE/ASTM SI 10 American National Standard for Metric Practice – named “primary” US metric standard the other standards should comply with. (I think I may be getting a copy)
Other “metric practice” standards like ANSI/IEEE 268 which is probably outdated by now.
ISO-31-0 apparently has “my” way of rounding somewhere in Appendix B Rule B.
None of them are drafting standards though.

The closest thing would be ASA Z25.1-1940 which is simply called “Rules for rounding off numerical values”, but I’ve had no chance to see what’s inside.

There are also lesser rules on the “urban legend” level, like “radius rule” – You round everything to even number because you may have to divide it by 2, like when calculating radius given the diameter.
“Ford ruler” – when Ford introduced decimal inches in 1932 the rulers were graduated in 1/50th of an inch because 1/100 would put too much strain on the eye. So second decimal must always be even, .38, not .37.

More input anyone?