Composite Position Calculation on a 12 X 4 Hole Pattern

[EngineeringPV]

I am doing a (48) 12 X 4 hole pattern with a composite positional tolerance
?0.004 ABC
?0.002 DE

the hole diameter is .1422 / .1424.

I have a few books on GD&T but i can not figure out how to calculate this. Either by CMM or by hand. I would rather do this by CMM as this is a lot of work with 48 holes to calculate.

 

[Jim Wynne]

Re: Composite Position Calculation

Welcome to the Cove.

It would be helpful if you could post a detail from the drawing you're dealing with. In general, when it comes to things like bolt circles, the top feature control frame applies to individual holes and the lower one pertains to the location of the circle itself. It's difficult to say what might be the case with your part though, without actually seeing the feature(s) and callouts.

 

[Michael_M]

Re: Composite Position Calculation

I am doing a (48) 12 X 4 hole pattern with a composite positional tolerance
?0.004 ABC
?0.002 DE

the hole diameter is .1422 / .1424.

I have a few books on GD&T but i can not figure out how to calculate this. Either by CMM or by hand. I would rather do this by CMM as this is a lot of work with 48 holes to calculate.

Without seeing the drawing, what this is saying to me is the hole must be within .004 to A B C and within .002 of D E. I assume the A B and C are datum's of the part and D and E are the holes themselves.

On a CMM, I would establish my datum's off A B C then measure 1 hole, then establish my datum's of D and E. Most parts I have seen that use this want the true position off A B C for one hole then all other holes must be off the 1 hole but without seeing the drawing and datum's, I cannot say this is certain.

 

[EngineeringPV]

Re: Composite Position Calculation

Attached is a part of the dwg. The ?.002 A|B should be D|E. I understand the top part of the tolerance. The bottom half is what is confusing me. Datum -D- is my origin when measuring everything with Datum E and my axis alignment. The second half of the composite tolerance deals with the rotational degrees of freedom if i am reading a book correctly, which is where i am confused. I have 4 rows of holes. And the tolerance is ? .002 which is not in degrees.

 

[Stijloor]

Re: Composite Position Calculation

Attached is a part of the dwg. The ?.002 A|B should be D|E. I understand the top part of the tolerance. The bottom half is what is confusing me. Datum -D- is my origin when measuring everything with Datum E and my axis alignment. The second half of the composite tolerance deals with the rotational degrees of freedom if i am reading a book correctly, which is where i am confused. I have 4 rows of holes. And the tolerance is ? .002 which is not in degrees.

What GD&T Standard is referenced in the title block?

 

[EngineeringPV]

Re: Composite Position Calculation

ASME Y14.5

 

[Stijloor]

Re: Composite Position Calculation

ASME Y14.5

1982? 1994? 2009?

 

[EngineeringPV]

Re: Composite Position Calculation

I knew i should have said something. There is no call out for a year. this is a relatively new part so i would have to say 2009 though

 

[Stijloor]

Re: Composite Position Calculation

I knew i should have said something. There is no call out for a year. this is a relatively new part so i would have to say 2009 though

What is confusing though is that the datum feature symbol (The capital letter "E" between the "wings") was used in the 1982 Standard. Can you clarify for proper interpretation?

 

[EngineeringPV]

Re: Composite Position Calculation

a coincidence. That was just me trying to separate them.