Tolerance of Position - Pattern of Holes at MMC - Datum Feature Reference

[optomist1]

Hi To All,

When using a a tolerance of position control on a pattern of holes at MMC and using this as a Datum Feature Reference, must a diameter symbol be used in the tolerance portion of the feature control frame?

Seems rather obvious, I need to be sure....

Regards,
Marty

 

[True Position]

Re: Tolerance of Position - pattern of holes

Hi To All,

When using a a tolerance of position control on a pattern of holes at MMC and using this as a Datum Feature Reference, must a diameter symbol be used in the tolerance portion of the feature control frame?

Seems rather obvious, I need to be sure....

Regards,
Marty

If you wish the tolerance of the pattern to be a circular zone are around the basic dimensions, yes.

 

[David DeLong]

Re: Tolerance of Position - pattern of holes

Hi To All,

When using a a tolerance of position control on a pattern of holes at MMC and using this as a Datum Feature Reference, must a diameter symbol be used in the tolerance portion of the feature control frame?

Seems rather obvious, I need to be sure....

Regards,
Marty

Marty:

If the pattern of holes are round, then the diametrical tolerance zone symbol is most appropriate. When I see a drawing with a pattern of round holes without the diametrical tolerance zone symbol in the feature control frame, I just feel that the Designer made an error.

If the holes are not round, let's say slotted, then the diametrical tolerance zone is not appropriate and should not be use.

 

[optomist1]

Re: Tolerance of Position - pattern of holes

Thank you David and TruePosition,

Studying for the Technologist exam...so I need to be clear. If given the previously described scenario; if a Diameter symbol is NOT USED, is the call-out technically incorrect?

Or is there a grey area?

Thanks again

Marty

 

[David DeLong]

Re: Tolerance of Position - pattern of holes

No, it is not wrong if we are still talking about a round hole. It means that the tolerance zone is square (X & Y axis) rather than round.

Good luck on the exam. It is really quite tough.

 

[optomist1]

Re: Tolerance of Position - pattern of holes

Thanks David....