Best Fit- Bore Pattern

[[Cl...]]

I was hoping someone could please explain this to me?
I've never used this best fit bore pattern. No idea how it
works or when to use it.

Thanks in advance.

[[Mi...]]

Hey Clarke,

Sometimes, in the dimensioning, I have a datum that consists of multiple holes. Through the best fit, I can generate a coordinate system that takes into account all the deviations of the holes.

I also use it when a hole pattern is only referenced to itself but with very tight tolerances. so it will calculate the rotation and translation based on your prefered "Best Fit Method". Usually i just go with Gauß. I am very certain that there are specific rules outlined somewhere in the Norms that dictate when to use certain Methods but i dont know them.

So basicly it takes all deviations in Position from alle the Features selected and calculates a new coordinate system where the selected Features fit "best"

Note: the generated coordinate system does only apear in the list where you can select it in an Element. There is no generated coordinate system in the characteristics.

[[Cl...]]

So, I tick those two options to allow translation and rotation? Or does that depend on the Datums the patterns referenced to?

[[Ma...]]

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You tick translation and/or rotation depending on the datums the pattern is referenced to. If you're pattern is fully constrained, you shouldn't tick either of these. If you're datum structure is not clocked, only tick rotation. If your datum structure is spatial only or refers to the pattern itself, tick both.

We usually use Chebyshev fit rather than Gaussian. This way the worst two elements in the pattern will have equal (and minimum) errors.

[[Cl...]]

OK, that explanation helps. Thank you all!

[[Jo...]]

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Mark Foster (AGI GD&Ttraining) refers to this as wiggle room. If you have a gage with the bolt pattern, the rotation/translation when allowed represents the ability to manipulate the gage until it goes thru holes. Those values of shift and rotation appear on plot.

[[To...]]

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Unless you have MMB/LMB on Datum Features, right?

[[Ri...]]

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MMB/LMB has no impact on if you want Rotation/Translation applied. Those are for the dimensioned features. If you tick either of them, you are Rotating/Translating from the Datum Structure.