True Position of holes, without Diameter symbol in Control Box??

let me lay this out for you guys and gals the best I can:

I have Datum A wich is a inside Circle recessed into the top of the part. We will call this "Datum A"

I have another recessed circle on the bottom of the part. We will call this "Hole"

"Hole" has a dimension callout that reads as follows: Dia. 7.06"
[T.P./.010/A] Notice there's no Dia. Symbol in the Cntrl Frame

I have never seen this callout before without the Dia. Symbol in the control frame when in reference to a datum that is a circle or cylinder, have you?

If I run this with both features as Circles, I get a measurment of 0 (ZERO)

If I run this with both features as Cylinders, I get some actual numbers, but I don't know if they are correct.

If I run this with Datum A as a Cylinder and Hole as a Circle, I get 0(ZERO)

I am confused as to which way i am supposed to do this. Is the callout on the drawing messed up, or am I giving Pcdemon incorrect features to calc this dimension?

Any help would be greatly appreciated.

Sam

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Wes Cisco over 12 years ago

So your saying that if datum_A on my part is only .060" thick and there are 30 holes spaced out over that plane Xactmeasure won't let me position them? With material that thin creating a cylinder is pretty much a time sink, both in programming and in execution. I've never NOT been able to report them with Xactmeasure.

I am aware of the standard but honestly with a touch probe the CMM is never truly measuring the entire length of a feature. Even with a scanning probe if that feature is not a thru hole you can't probe it right up to the surface it intersects. The point could be argued and in my opinion my information was not incorrect.

Material that is only .060" thick is not typical of most situations. In that case your assessment is correct from a cost effectiveness perspective.

I just checked v2011mr1 and you are correct it does allow circles. When I took the Pc-Dmis GD&T class in Oct. of 2010 circles were not allowed. I have pulled my course book and reviewed my notes from the instructor stating just as I did previous why there were no circles allowed for position.

The standard was not written with the intention that Co-Ordinate Measure Machines would be the main tool used to evaluate whether or not parts were compliant with drawing requirements. Rather the standard expressly anticipates surface place, height gage, & dial test indicator inspection. (This is key to why Pc-Dmis does not evaluate Concentricity per the standard BTW.) It is up to us CMM programmers to find ways to use the CMM to meet the standard's requirements.
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Wes Cisco over 12 years ago

So your saying that if datum_A on my part is only .060" thick and there are 30 holes spaced out over that plane Xactmeasure won't let me position them? With material that thin creating a cylinder is pretty much a time sink, both in programming and in execution. I've never NOT been able to report them with Xactmeasure.

I am aware of the standard but honestly with a touch probe the CMM is never truly measuring the entire length of a feature. Even with a scanning probe if that feature is not a thru hole you can't probe it right up to the surface it intersects. The point could be argued and in my opinion my information was not incorrect.

Material that is only .060" thick is not typical of most situations. In that case your assessment is correct from a cost effectiveness perspective.

I just checked v2011mr1 and you are correct it does allow circles. When I took the Pc-Dmis GD&T class in Oct. of 2010 circles were not allowed. I have pulled my course book and reviewed my notes from the instructor stating just as I did previous why there were no circles allowed for position.

The standard was not written with the intention that Co-Ordinate Measure Machines would be the main tool used to evaluate whether or not parts were compliant with drawing requirements. Rather the standard expressly anticipates surface place, height gage, & dial test indicator inspection. (This is key to why Pc-Dmis does not evaluate Concentricity per the standard BTW.) It is up to us CMM programmers to find ways to use the CMM to meet the standard's requirements.
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