Limited Length 1.7.3 ASME Y14.5 M-1994

[SDETERS]

I have a place where I need to callout a limited length on a drawing. Easy enough. But the standard says I need to call out a dimension for the length. Will the dimension that calls out the length be a basic or will it have a tolerance? I guess the .200 dimension in the example PDF is what I am questioning. Thanks.

 

[ewh]

If it is basic, how do you specify the tolerance allowable?

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[SDETERS]

Well I was thinking of the dimension to be simliar to a gage dimension on a taper? It is not a critical dimension if I put a tolerance that would be ok also. I was just wanting to get the proper way of calling the dimension out.

Thanks

 

[KENAT]

It needs a tolerance, and typically I'll put a fairly loose one for most applications such as areas required to be paint free etc.

As ewh points out there is always some kind of tolerance whether it be direct or from some form of GD&T. On a gage dimension on a taper, the tolerance for the resultant surface is still there just expressed in a different way.

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[SDETERS]

Would adding a Min to the .200 Dimension work in this Example? I think this is as loose as it gets. Thanks for the feedback.

 

[KENAT]

Maybe, but by saying Min you are saying it can be anything from .200 to the entire width of the surface/part, is that acceptable?

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[ctopher]

...and datum A should be called out once.

Chris
SolidWorks 09 SP4.1
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[SDETERS]

KEnat
Yes This will be acceptable.

What is happening on this part is that there is a small amount of draft on the od. As long as the B datum per the .200 is in tolerance we will allow the rest of the part to vary per the tolerance specified on the other end. So what we are trying to accomplish is to have nore tolerance on one end of the part than the other to allow for the small amount of draft that is produce during the anufacturing process.

 

[SDETERS]

Please view pdf with all comments applied per this thread. I do appreciate the help. This drawing is a simplified.

 

[KENAT]

Should the Right hand FCF reference B for coaxiality?

Not somehting I recal ever really dimensioning though, I think it's addressed in the standard.

Posting guidelines faq731-376

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(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Belanger]

I always thought it's kind of funny how ASME allows basic dims (with no tolerance of any kind) for gage dimensions, and then they state that "established tooling or gaging tolerances apply" (para. 4.6.2 of Y14.5M-1994).

So I guess basic dims can be used to show a limited length, but it necessarily implies that the manufacturer have some documentation on hand about how accurate that needs to be.


John-Paul Belanger
Certified Sr. GD&T Professional

http://www.gdtseminars.com

 

[fsincox]

ASME Y14.5M-1994, 1.7.3 Limited Length or Area Indication
states in part ".. within limits specified on the drawing, ..". I would interperet that as saying the limits are specified. Datums are basic.

 

[ewh]

I always thought that using "established tooling or gaging tolerances" was strange also, but have to admit to taking advantage of it occasionally.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[MechNorth]

If you don't specify a +/- tolerance on the .200 dimension, then it will default ot gage maker tolerances, which may well be significantly tighter than you need. There are published values for gage maker tolerances, based on International Tolerance classes (ITs), and a default class when none is specified. A potentially expensive way to go here.

Jim Sykes, P.Eng, GDTP-S
Profile Services

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TecEase, Inc.

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[fsincox]

MechNorth,
Do you have a specification number or document reference for this, I am very interested in the uses of the "IT" system.
Frank

 

[MechNorth]

ANSI B4.4 - Inspection of Workpieces provides Gagemaker Tolerances.

Machinery's Handbook also references B4.4 and gives a goodgraphic description of the Gagemaker's zones vs overall tolerances.

Hope that helps.
Jim

Jim Sykes, P.Eng, GDTP-S
Profile Services

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TecEase, Inc.

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[fsincox]

Jim,
Thank you.
Frank

 

[fsincox]

John-Paul,
I always thought of it as kind of a: "be as careful as you can but we are not going to restrict you to a particular amount of careful, just do your best" kind of thing. I really think that is about it.
Frank