Tolerances and decimal places
Tolerances and decimal places
(OP)
I would like to know what your opinion is regarding the number of decimal places of form tolerances. ASME Y14.5 says that inch dimensions and their tolerances should have the same number of decimal places e.g. .500±.125 or .3125±.0010. Now, if we add a form tolerance, say circularity. Should the form tolerance have the same number of decimal places? For instance, if the dimension is .3125 +.000/-.0030, should the circularity be .0010 or .001?





RE: Tolerances and decimal places
See para 2.3.2(d) of ASME Y14.5M-1994.
RE: Tolerances and decimal places
Also, check your CAD settings, some are set to drop the trailing zero.
Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog
RE: Tolerances and decimal places
"Wildfires are dangerous, hard to control, and economically catastrophic."
Ben Loosli
RE: Tolerances and decimal places
RE: Tolerances and decimal places
Dave D.
www.qmsi.ca
RE: Tolerances and decimal places
RE: Tolerances and decimal places
Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog
RE: Tolerances and decimal places
If you interpret this as meaning that tolerances other than positional are exempt because they are not specifically referred to, you are going to have quite a few problems applying and understanding this standard.
Please refer to para 1.1.4.
RE: Tolerances and decimal places
" For instance, if the dimension is .3125 +.000/-.0030, should the circularity be .0010 or .001? "
My understanding of the standard is that it should be:
.3125 +.0000/-.0030 cirulariy .0010
The common element on all 4 cases in 2.3.2 is that the tolerance has the same number of figures as the dimension.
KENAT, probably the least qualified checker you'll ever meet...
RE: Tolerances and decimal places
RE: Tolerances and decimal places
Hole size: .3125 +.000/-.0030 inches,
Should the circularity be .0010 or .001? As state above you agree it should me .0010. Right?
Now, if the TP of the hole is .1 and the basic dimensions locating the feature from two sides of the part are 1.0 and 2.0 respectively. As they are (.1, 1.0, 2.0), they comply to para 2.3.2(d) of ASME Y14.5M-1994. Should these be also four decimal places (TP = .1000 and 1.0000 and 2.0000)?
RE: Tolerances and decimal places
yes, circularity should be .0010
Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog
RE: Tolerances and decimal places
RE: Tolerances and decimal places
KENAT, probably the least qualified checker you'll ever meet...
RE: Tolerances and decimal places
Reduce errors, stay consistent.
Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog
RE: Tolerances and decimal places
As for the OP's second clarification, I think that if the positional tolerance can be stated using one decimal place, the associated dimensions could also be one decimal place. The decimal places of the locating dimensions would still be the same number as that of the related tolerance.
RE: Tolerances and decimal places
Let's review:
We agree that the size dimension and tolerance should have the same number of decimal places: 3125 +.0000/-.0030 (para 2.3.2(b) of ASME Y14.5M-1994).
We agree that the "tolerance can be stated using one decimal place, the associated dimensions could also be one decimal place. The decimal places of the locating dimensions would still be the same number as that of the related tolerance.". Thus, TP = .1 and basic dimension = 1.0, 2.0 is correct (para 2.3.2(d) of ASME Y14.5M-1994).
I would say that form tolerances should have the same decimal places as the size dimension of the FOS or non-FOS they define. I will call this rule "good practice" but it is not in the standard (circularity of .0010). Do you agree?
RE: Tolerances and decimal places
I have learned to keep a somewhat open mind when it comes to understanding this standard. Different situations call for different solutions and the standard does not cover every possible situation, but does define the basic groundwork on how to approach them.
RE: Tolerances and decimal places
JV1 I would go a little further and say it was implied by the standard but not explicitly stated.
KENAT, probably the least qualified checker you'll ever meet...