A center of pattern of 4 Holes on Datum-A

[Jignesh]

I wanted to find a center of pattern of 4 Holes on Datum-A. So, I created by Construct filter feature in which I selected all 4 Holes. I checked the created feature SCN1 which has exact Theoretical coordinates what it should have as per drawing. Is this the way I need to create center of pattern of 4 Holes? Then, I measured True position of Center which showed me True position of all 4 Holes with center in Report window. Please, let me know.

[Jignesh]

Sorry, I created a center by Construct Feature Set not Construct Filter Feature. Could one of you please suggest the opinion for the above issue?

[JEFMAN]

Why don't you create a circle from holes centers ?
Then use this circle as datum ?

[Jignesh]

Hi Jef, How can I create a circle from Holes centers? Do I need to use Construct feature set or just select circle from construct features? I tried to create from construct features, but it did not work because window appeared, math does not converge.

[Mike Ruff]

Hi Jef, How can I create a circle from Holes centers? Do I need to use Construct feature set or just select circle from construct features? I tried to create from construct features, but it did not work because window appeared, math does not converge.

Make sure you are in the correct workplane when you construct the circle and it should work.

[brian.freeman]

This might help you out:

CIR_22 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
THEO/<5,1,0>,<0,0,1>,0.25
ACTL/<5,1,0>,<0,0,1>,0.25
TARG/<5,1,0>,<0,0,1>
START ANG=0,END ANG=360
ANGLE VEC=<1,0,0>
DIRECTION=CCW
SHOW FEATURE PARAMETERS=NO
SHOW CONTACT PARAMETERS=NO
CIR_23 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
THEO/<5,-1,0>,<0,0,1>,0.25
ACTL/<5,-1,0>,<0,0,1>,0.25
TARG/<5,-1,0>,<0,0,1>
START ANG=0,END ANG=360
ANGLE VEC=<1,0,0>
DIRECTION=CCW
SHOW FEATURE PARAMETERS=NO
SHOW CONTACT PARAMETERS=NO
CIR_24 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
THEO/<3,-1,0>,<0,0,1>,0.25
ACTL/<3,-1,0>,<0,0,1>,0.25
TARG/<3,-1,0>,<0,0,1>
START ANG=0,END ANG=360
ANGLE VEC=<1,0,0>
DIRECTION=CCW
SHOW FEATURE PARAMETERS=NO
SHOW CONTACT PARAMETERS=NO
CIR_25 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
THEO/<3,1,0>,<0,0,1>,0.25
ACTL/<3,1,0>,<0,0,1>,0.25
TARG/<3,1,0>,<0,0,1>
START ANG=0,END ANG=360
ANGLE VEC=<1,0,0>
DIRECTION=CCW
SHOW FEATURE PARAMETERS=NO
SHOW CONTACT PARAMETERS=NO
ASSIGN/V1=ARRAY(CIR_22.D,CIR_23.D,CIR_24.D,CIR_25.D)
ASSIGN/V6=SORTUP(V1)
ASSIGN/V7=V6[1]
SCN2 =FEAT/SET,CARTESIAN
THEO/<4,0,0>,<0,0,1>
ACTL/<4,0,0>,<0,0,1>
CONSTR/SET,BASIC,CIR_22,CIR_23,CIR_24,CIR_25,,
F1 =GENERIC/CIRCLE,DEPENDENT,CARTESIAN,IN,$
NOM/XYZ,<SCN2.TX,SCN2.TY,SCN2.TZ>,$
MEAS/XYZ,<SCN2.X,SCN2.Y,SCN2.Z>,$
NOM/IJK,<0,0,1>,$
MEAS/IJK,<0,0,1>,$
DIAMETER/0.25,V7

[Jignesh]

Thanks for the guidance. I have only last question about topic. If drawing indicates True position of each Hole has to be measured, I think I can create Construct feature set SCN1 of 4 holes to find True Position of all 4 Holes at once, right? I have measured this way and actual coordinates of all 4 Holes in Report window are matched with actual coordinates of all 4 Holes shown in Edit window respectively. So, I think there is nothing wrong this way.

[Jignesh]

Please. Let me know because True position is just with reference to Datum-A, so when I find the True position of holes individually. it always give me zero value of True position. But, when I find by construct feature set, it really gives me True position values. The holes are located on Datum-A and drawing does not consider sides of Datum as a Datum-B and C. Could one of you please let me know about it?

[JEFMAN]

Can you post a scheme, or the drawing, please ?

[Jignesh]

The Holes Dia. = 8.85 +/- 0.3MM. Datum-A is the surface where the Holes are located.

[SingularitY]

That print is showing a true position of a pattern in relation to A. True positioning the center of the pattern is not what they're going for here. Since it is a 4x feature, this is the thought process...
Go in order of precedence in the feature control frame. Start with the first datum. What degrees of freedom can it constrain? It must constrain. What degrees of freedom can the second datum constrain that the first isn't already constraining? It must constrain. And so on. If the feature control frame does not constrain all 6 degrees of freedom, then the feature in question constrains the rest of the degrees.
in this case, Datum A is your level and origin in one axis. The hole pattern itself is your rotation and origin in the other 2 axis. I use 2 alignments for this so nominals show how I want it..
Construct a line from 2 opposing circles. Level and origin to A, rotate to the line, origin in 2 axis to one of the holes used for the line.
Create a best fit alignment using all 4 holes. The alignment should recall the previous alignment. 2D best fit rotation (which is rotation AND translation in 2 axis) about the axis you leveled to, using Least Squares, hit compute and create. This is your final alignment.
Dimension T/P of each hole separately.

[JEFMAN]

In this case, i would say that the location could be replaced by a perpendicularity to datum A.
There's no indication of CZ (common zone), so each hole should be dimensionned individually.
Datum B should be an assembly of 4 pins which fits the 4 holes with boxed dimensions 34 (in ISO world !).

Be carefull, the datum B is never called after A, so the perpendicularity of B to A is not constrained.

Just my opinion...

[Rich P]

True Position 0.5 B is not attached to a feature of size, a surface, is this a legal ISO callout? Is this an ISO drawing?
All true positions are attached to centerlines or surfaces, ASME I am calling foul on all Positions except 4X 8.85 diameters.

[JEFMAN]

True Position 0.5 B is not attached to a feature of size, a surface, is this a legal ISO callout? Is this an ISO drawing?
All true positions are attached to centerlines or surfaces, ASME I am calling foul on all Positions except 4X 8.85 diameters.

You're right for the 0.5 B, it doesn't make sense (except to localize B from the side, but a 17 boxed is missing !).
I would say 2.5 to A is right, for others positions, info are missing...
As often, the drawing is not ISO nor ASME, it's an "own designer standard !"

I'm usually surprised by the low level ogf GD&T that we can find on drawings...