Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
(OP)
Where in ASME 14.5 does it state we can add & subtract Basic Dim's. without tol. accumulation? I know we can, I just can not find a direct statment in the Std. (Venders say no).
Thanks All,
Thanks All,





RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
There are definitions and explanations that when considered in concert with one another support the outcome of the statement.
1.3 Definitions > 1.3.9 Dimension, Basic … used to describe the theoretically exact...
1.4 Fundamental Rules (a)… (or indirectly in the case of basic dimensions), …
5.2 Positional Tolerancing (a) … (theoretically exact) …
5.2.2 Application to Base Line and Chain Dimensioning … For positional tolerancing, unlike plus and minus tolerancing …
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
Powerhound, GDTP-T
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
I do not think there is a mention anywhere in ASME Y14.5M-1994 about adding and subtracting basic dimensions. Why should there be? The standard explains what they mean, and you can apply this to your arithmetic.
True position tolerances and profile tolerances usually relate each feature to common datums. It is bad practise to show feature to feature dimensions on such a drawing, but the tolerances are from the datums, regardless. Your addition and subtraction of the basic dimensions is exact. Tolerances are not accounted for.
If you have a bunch of holes located to true position, the distance between any two holes varies by the true position tolerance. This can be verified by simple geometry.
JHG
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
It sounds as if your vendors want to get out of a situation that they find uncomfortable, and are grabbing at straws.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
Gary, I will be 72 on October 10th using GDT since 1953.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
I don't see the connection. I think that would still be considered double dimensioning, whether it is a basic dimension or a toleranced dimension. It would only serve to obfuscate the drawing if it weren't a reference dimension, datum or not.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
We had a magnified detail on a printed circuit board where the basic dimensions showed up again and we could have made them reference for double dimensioning, or not.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
They are theoretically exact. The tolerance comes from the position, profile or other tolerance of the feature/datum target itself.
If you are basically talking about relating one hole to another or that kind of thing then you can add and subtract them all day and the resultant value is theoreticaly exact.
It is sometimes necessary to add/subtract them when doing tolerance checks, designing mating parts etc. Normally for inspection I'd hope you were measuring the actual dimension but I suppose this may not always be possible/easy, however, your measurement accuracy would take a hit.
In what context is the Vendor saying you can't add/subtract them, is it related to inspection?
KENAT, probably the least qualified checker you'll ever meet...
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
Thanks all for your comments.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
This callout does not refer to a datum to hold the profile relative to?
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
Are you saying you have a profile which as a basic dimension to it ie a radius for instance, if so there should be a tolerance given for the radius of that profile,
you cannot ask a manufacturer to produce a component to an exact dimension and not give a tolerance.
regards
desertfox
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
What is the context of your question? If you are calculating the nominal distance between two features controlled by basic dimensions, there is no tolerance. If you are calculating the distance between two as-measured features controlled by basic dimensions, there is a tolerance. Each feature is controlled from the datums you specified.
If you are specifying profile tolerances, datums are mandatory.
If you have a copy of ASME Y14.5M-1994, take a look at Figs_6.20 and_6.21. These show methods of calling up nominally co-planar surfaces.
JHG
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
A simple circular pattern of features may be specified 5X with a basic diameter of xx.xxx and an angular displacement of 5/360 with one feature shown coincident with the centerlines… or displaced xx.xxx degrees from it. That specification would yield X and Y basic coordinates for measurement that are not directly specified.
On angled or compound gun-drilled passages in structures designers often detail the end-points with basics normal to the plan views where the passage intersects other features (spot faces, ODs, IDs, surfaces, etc.) rather than rotating and specifying the basics normal to the gun-drilled hole itself albeit for expedience sake. Inspectors must figure the basic displacements normal to the specified feature with respect to the DRF to measure the hole’s position deviation and then convert the axial displacements at each end of the hole where they would intersect the basic value of the intersected feature just so their “basic value displacements” match up with those specified by the designer. All of this is to satisfy an edict from an STA that the measurement results relate directly to the “ballooned” basic dimensions
There are so many other reasons why the basics are specified in ways other than the way they must be figured with respect to the specified DRFs (if there are position requirements to multiple DRFs to limit stack accumulation, etcetera, etcetera, etcetera) but they all describe the exact theoretical form, location and/or orientation relative to the basic contour and/or DRFs they are scrutinized to so they can be manipulated mathematically all day long to accomplish the scrutiny that one is interested in performing!
Paul
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
For the profile question see: http://www.cmmtalk.com/welcome.htm > GD&T > profile_surface_coplanar.
Paul
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
Have a look at this site:-
http://ww
RE: Where in ASME 14.5 does it state we can add & subtract Basic Dim's.
http://ww
How do we post a PDF (or other) file or part of a Drawing or Sketch as part of posting a question-it would be a great tool. Can it be done?
Thanks all for your input-it helped in determining that there is no place in ASME 14.5 Std. that states directly that we can add & subtract Basic Dim's. but other statments support it.