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 if the cylinder is say 1.00" deep and is not a thru cylinder/Ø and you probe that cylinder at 3 levels 1.) .020" 2.) .500" 3.) .800" even though there is .200" of that cylinder that has had no probe hits it's TRULY being defined over the length. I agree that DMIS does attempt it but it is calculations based on the points taken.

IMNSHFO, you need to learn more about ASME Y14.5 GD&T if you are going to be giving advice on it.

Position does not control the surface of the cylinder, but rather it's axis. Even though you can not touch .2" of your theoretical cylinder, you have picked up .8" of it's axis and unless you have reason to suspect the the axis of that last .2" deviates greatly from the rest, you have enough to make a pretty good evaluation. As the CMM programmer part of your job is deciding whether or no that .8" is adequate and if not, finding another way, whether on the CMM or not. The CMM is not the only tool for inspection and in several cases is not the best tool.

Please understand I am not trying to pick on you, or make myself look good by making you look foolish. I am trying to prevent misinformation being posted without contest.

If I am measuring a cylinder that has been created by circle interpellation and the tool breaks down as it reaches that last .200" of the cylinder depending upon where I probe that cylinder will determine if that is detected. I understand and agree with the standard but DMIS can only calculate with data it is given and the data is coming from where the probe touches the part. This is why I suggested that I would want to know the function of the feature, so that I can inspect it at the appropriate level. It's the same on surface profiles. I can take a point every .100 on a grid but it can still miss excess material from the machine that just happend to jump one line of code while 3D'ing a surface leaving a .030" x .030" stripe across the part or a chip that causes a gouge on one pass of the tool. I have no claims to being an expert, it's just the way my mind see's it, and I truly mean no offense to anyone.

As the CMM programer, and as an inspector, it is up to you to know, or learn, the methods of production used to create the parts you must inspect. That knowledge is a key part of knowing how much and which areas need the most attention to achieve the ultimate goal which is verifying and documenting the part meets the drawing requirements as interpreted be ASME Y14.5 or whichever standard is stated on the drawing or in the customer's specifications.

A solid understanding of GD&T is as important as knowing how the features were machined and how they will function. Your comments demonstrate you do not have that knowledge of GD&T. No one is born with it. Just please be careful giving advice to others about GD&T until you can cite page and chapter from the standard to support your interpretation if need be.
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Wes Cisco over 12 years ago

So if the cylinder is say 1.00" deep and is not a thru cylinder/Ø and you probe that cylinder at 3 levels 1.) .020" 2.) .500" 3.) .800" even though there is .200" of that cylinder that has had no probe hits it's TRULY being defined over the length. I agree that DMIS does attempt it but it is calculations based on the points taken.

IMNSHFO, you need to learn more about ASME Y14.5 GD&T if you are going to be giving advice on it.

Position does not control the surface of the cylinder, but rather it's axis. Even though you can not touch .2" of your theoretical cylinder, you have picked up .8" of it's axis and unless you have reason to suspect the the axis of that last .2" deviates greatly from the rest, you have enough to make a pretty good evaluation. As the CMM programmer part of your job is deciding whether or no that .8" is adequate and if not, finding another way, whether on the CMM or not. The CMM is not the only tool for inspection and in several cases is not the best tool.

Please understand I am not trying to pick on you, or make myself look good by making you look foolish. I am trying to prevent misinformation being posted without contest.

If I am measuring a cylinder that has been created by circle interpellation and the tool breaks down as it reaches that last .200" of the cylinder depending upon where I probe that cylinder will determine if that is detected. I understand and agree with the standard but DMIS can only calculate with data it is given and the data is coming from where the probe touches the part. This is why I suggested that I would want to know the function of the feature, so that I can inspect it at the appropriate level. It's the same on surface profiles. I can take a point every .100 on a grid but it can still miss excess material from the machine that just happend to jump one line of code while 3D'ing a surface leaving a .030" x .030" stripe across the part or a chip that causes a gouge on one pass of the tool. I have no claims to being an expert, it's just the way my mind see's it, and I truly mean no offense to anyone.

As the CMM programer, and as an inspector, it is up to you to know, or learn, the methods of production used to create the parts you must inspect. That knowledge is a key part of knowing how much and which areas need the most attention to achieve the ultimate goal which is verifying and documenting the part meets the drawing requirements as interpreted be ASME Y14.5 or whichever standard is stated on the drawing or in the customer's specifications.

A solid understanding of GD&T is as important as knowing how the features were machined and how they will function. Your comments demonstrate you do not have that knowledge of GD&T. No one is born with it. Just please be careful giving advice to others about GD&T until you can cite page and chapter from the standard to support your interpretation if need be.
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