Bolt pattern best fit

[[Cl...]]

I've never had to use this option in Calypso just because of the parts we make. In the event I do need it someday. I'd like some clarification. Say I have a round part (OD) with a smaller ID in the center we'll call datum B. The face of the OD is datum A the
circle has 6 equally spaced holes with the one at 12:00 as datum C. Each hole has a position callout back to A B C. (Part is in the XY work-plane). I'm not clear on which axis to allow to rotate/translate?

Thanks in advance

[[Ma...]]

If it's fully defined callout, then you can not use any translation and/or rotation.
If there is datum in callout which is made out of pattern, then you can only rotate in main axis - in this ex. datum A .

Datum A in this case is a plane, so it's vector is your rotational axis. Datum B gives you center point and C is for bestfit rotational.

[[Ma...]]

As you described it the hole pattern would be fully constrained by the DRF, therefore no shift or rotation would be allowed.

[[Cl...]]

So, if datum C wasn't there, I could allow rotation around Z?
If datum B wasn't there, I could allow translation in X&Y?

[[Ma...]]

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Normally with full DRF you can not allow any translation/rotation.

But here you have pattern as part of DRF so you have to make alignment from bestfit pattern to gain base C. Then you can TP individual holes ...

[[Mi...]]

Unless it's different in the newest Calypso, you don't get to pick which axis the rotation happens around in the Best Fit of Bore Pattern. You simply choose to allow Rotation or Translation. I hope it is different in the new GDT Engine as sometimes it seems to pick the wrong axis to rotate around in certain cases...

IF you're using a 3D Best Fit Alignment or Geometry Best Fit Alignment then yes you pick all the individual axes but that's a lot more work to do correctly since you first need a secondary alignment setup correctly, then the best fit... then you would have to report all your holes to that best fit alignment individually...

[[Cl...]]

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Thanks Michael. In Virtual DMIS, the software I started on back in 1999. I don't believe it had any such option.
If a bolt pattern was called out, it was always a fully constrained DRF. Plane/Circle/Clocking feature and
holes 360°. I'd simply rotate to each hole one at a time and report position. Like I said due to the type of
parts we make, I'll probably never need it, but I'd like to know it anyway.

[[Mi...]]

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Well, in Calypso, as per ASME and the simultaneous requirement *technically* you should be still using the BFBP for a pattern of features (doesn't have to be circles), even with a fully constrained control frame, you just disable Rotation and Translation. When you do this with a PiWeb report you automatically get an extra characteristic that is your worst result.

Doing a separate Position characteristic, and rotating for each hole is less correct...and more work anyway.

[[Ma...]]

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To be slightly more precise:
If datum C wasn't there you would allow rotation.
If datums B and C weren't there you would allow translation and rotation.

[[Ma...]]

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Datums C is in this case pattern itself

[[Ma...]]

Datums C is in this case pattern itself
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I believe in the original post, datum C was described as one particular hole of the pattern.