Tool Design Environment: Is anyone using Geo Tol true position of zero at MMC to locate mating details? Opinions?
You can. However, since it is applied to a hole you should have the diameter symbol in front of the value which defines the form of the locating region. When using MMC you are no longer defining the axis of the feature but rather the outer profile/wall.
Newell-good info. How would you call it out? Would you give tolerance (ie .0004) at RFS?
Newell Voss wrote: .... When using MMC you are no longer defining the axis of the feature but rather the outer profile/wall.
Newell Voss wrote:
.... When using MMC you are no longer defining the axis of the feature but rather the outer profile/wall.
That isn't actually true Newell. You tolerance still applies to the axis. It is just that, now the tolerance changes based on that actual measured size of the hole.
If you hole size tolerance is .250"/.258" and you have a position tolerance of Dia .005" @ MMC, then your position tolerance now changes based on the actual measured size.
So, if the measured size of the hole comes to 0.250, then your positional axis tolerance is a diameter of .005".
If your measured size is 0.255, then now your positional axis tolerance is a diameter of 0.010" (.005 + the diameter MMC shift of .005")
If your measured size is .258, then now your positional axis tolerance is a diameter of 0.013" (.005" + the diameter MMC shift of .008")
So, using a positional tolerance of Dia 0" at MMC, it just shifts your smallest holes size to a tolerance of 0"
I've seen the zero a few times on medical component prints.
Newell is correct on the diameter symbol.
The real problem comes when you need to PPaP the part and need to produce the hole as close to mean as possible. Good luck holding a cpk on that one.
That is the hardest part about using this tolerance callout.
The diameter symbol is an omission. To be clear, this is for fixture/gaging not product. Jig grinding is usually used to achieve
We have a Production part in which the customer has this on the print:
Needless to say....this was a nightmare until we developed a good process for it. temperature controlled the entire way.
I'm surprised the perpendicular has only a primary datum.
If I find the prints with the located within zero callout I'll post a picture.
A side issue, but is the lower right hole not dimensioned yet or should the dim in question be 2X?
Also, ASME's Dimensioning and Tolerancing Principles for Gages and Fixtures, standard Y14.43 - 2011 may provide further insight for your requirements.
Y14.43 - Dimensioning and Tolerancing Principles for Gages & Fixtures - ASME
Without any data on the mating part, GD&T replies to the OP question will be mainly supposition.
As Dan correctly pointed out, at MMC you get no breathing room...zero slop. Is this a requirement for the mating part?
Attached is the mating detail. It's located by a standard dowel.
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