Tolerance question
Tolerance question
(OP)
I recently came across the drawing with 2 decimal tolerance on 3 decimal dimension, eg: .567 +/-.01,it is a machine part, I can't see the logic having 2 decimal tolerance here, am I missing something? (the tolerances specified on drawing are .XX +/-.05 and .XXX +/-.005), thank you for your input





RE: Tolerance question
"Where bilateral tolerancing is used, both the plus and minus values and the dimension have the same number of decimal places."
So you're right; they should have stated .567 ± .010.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Tolerance question
RE: Tolerance question
RE: Tolerance question
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Tolerance question
RE: Tolerance question
FYI -- They ain't cheap! For either the PDF version or the traditional paperback version, the Y14.5 standard is $170.
Which makes me think of another question for the group: Has anyone else noticed the PDF version for real cheap on eBay? It's like 29 bucks -- are those illegal Chinese knockoffs?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Tolerance question
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Tolerance question
May I ask : same number of decimal places you referred to is standard Y14.5 1994 or 2009 version, its true for 1994 version, I am not quite sure are there any changes in 2009 version, I don't have 2009 standard on hand.
But, I know there is a change on feature control frame callout in 2009 version, geometric tolerances and the basic dimensions may have unequal decimal places. For example :
POS|Ø.010 circle M|A|B|C-----1994 version
POS|Ø.01 circle M|A|B|C-----2009 version
SeasonLee
RE: Tolerance question
I see that the 2009 edition didn't change the rule for ± tolerances, though.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Tolerance question
RE: Tolerance question
There may be a good reason to have 567+-.010. Without knowing the application it's not possible to say. You can't just use rules of thumb that 'if it has a significant figure at the third decimal it must need a tight tolerance' or similar.
I'll sometimes do a 3 place decimal conversion of a fractional size, say .375 for 3/8, however may only need +-.010 or even looser on it functionally and will specify that.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Tolerance question
The designer had determined that the part won't function correctly if that feature is smaller than .557 or larger than .577.
RE: Tolerance question
This is what I would understand if the dim callout says .567+/- .010, but does .567 +/- .01 really imply .557 to .577 and not .55X o 57X?
RE: Tolerance question
RE: Tolerance question
.567+.01=.577
RE: Tolerance question
However, the fact this is causing confusion shows one reason for the rule in the first place which hadn't really occurred to me before.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Tolerance question
Thank you, I had not noticed that change yet either.
Frank
RE: Tolerance question
Not:
"shall have the same number of decimal places"
"should be shown with the same number of decimal places"
"must be written with the same number of decimal places.
It's
"have the same number of decimal places"
Shown or not, assume that the insignificant trailing zeros are there and do the arithmetic.