Feature control frame with basic dimension for coplanar surfaces?

[gageblockhead]

Dimensions are in mm. What would the tolerance be for the feature control frame "3.730 8x" dimension? The block tolerance on the print is +/- 0.125mm. I am told that the print block tolerance does not apply. I have never seen T.I.R in a feature control frame for flatness or parallelism with a basic dimension framed for the distance. What is the tolerance of the 3.730 8x dimension?

 

[SeasonLee]

It's very hard for us to image what it looks like for a section view only, would you mind to post a whole picture.

I have never seen not only TIR in a FCF but also the datum (-A-) and quantity (8X) callout, what standard apply for the print ? Y14.5 or ISO ?

SeasonLee

 

[Belanger]

Yes -- more info is needed. But it looks like the Y14.5 standard is being used. There are some non-standard things being done here (such as TIR). Also, the 3.730 dimension shouldn't be basic unless there is something else outside of our picture that addresses that distance (parallelism and flatness never use basic dims).

If coplanarity it desired, then profile of a surface would have to be used.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[desertfox]

Hi gageblockhead

I won't comment on Y14.5 as I am not familiar with it but here is my interpretation of the section drawing you have posted:-

TIR = Total Indicator Reading

8x = feature is in 8 different positions

So the parallel tol 0.1 for the 3.730 basic dimension means that the dimension can be 3.68 or 3.78 and that is repeated 8 times over the component.

desertfox

 

[powerhound]

JP is right about the basic dim on the parallelism. As shown, the basic dimension is incorrect, thus there is no legal interpretation of the parallelism requirement.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X4
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[flash3780]

I'm not sure why they didn't use a ± tolerance on the 3.730 dimension; perhaps there is a profile somewhere tolerance that isn't shown in this view? Maybe they left it off?

TIR is total indicator reading, but I think it's extraneous and doesn't add anything to the print.