LSQ VS Max Inscribed Element VS Minium Circumscribed Element

[[Ra...]]

Measurment is for a circular bushing where the diameter is close to 7mm. When i preview the results

Max inscribe element = 7.07
LSQ = 7.14
Minimum Circumscribed Element = 7.33

400 degrees angle range
Around 259 points.
No Filters/ No outliers

1.For functional check to where something fits into this bushing , you would use max inscribe element correct?
2.Shouldnt my max inscribe be bigger than lsq?

[[Cr...]]

Max inscribed will essentially tell you what the largest gauge pin will fit into your hole so yes you would want to use this for function. It will typically be smaller than LSQ. LSQ to my understanding is an average.

[[Da...]]

I would verify it with a pin gage to see which is giving you more accurate results.

[[Ke...]]

It is easier to use Outer Tangential, instead of Max Inscribed or Min Circumscribed.
It will give you the same results as the other two methods, without needing to figure out which you need... which is easy enough, after you learn the nomenclature; but it's nice when you are writing programs with dozens of ID and OD holes,

[[Al...]]

Hello guys, I've got a question about using these calculation techniques.

I don't like my stylus waste time on measuring same feature twice (first time as LSQ feature, second time as Max Inscribed Element) so I've scanned my circle as LSQ feature and then created second circle in which I recalled feature points from circle1, then I've changed circle to from LSQ to Max inscribed element, but the measurement is off pretty much (for H7 tolerance).

For example, if I measure 24H7 as LSQ I'll get 24.01mm and then I'd add roundness characteristic which gives value of 0.004mm,

if I measure it again using MIE I'll get 24.006mm (which confirms what I'd expect to see),

but if I recall feature points of circle 1 instead of measuring it again I get something like 23.995mm.

What's the deal with that, why is it so imprecise or what do I need to tweek to get similar results to 24.006?

Thanks in advance.

[[Mi...]]

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Have you set again the filter and outlier elimination on the recalled feature points?

[[No...]]

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Is there a special reason why you scan the features twice just to switch between LSQ and Max Inscribed? Because you can set all these parameters (plus filters and outliers) in each characteristic without changing anything in the feature.

When you recall feature points you have to set filters and ouliers again. Recalled points are always "raw" (unfiltered).

[[Al...]]

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That's it!!
No, I didn't and now that I did, it is totally the same as if I've measured it again.
Many thanks for the help!!!
Sometimes simplest things are easiest to miss.

[[Al...]]

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Thank you very much!
I didn't want to measure same feature twice I wanted to report both diameters, one as a LSQ feature, other as MIE feature.

[[No...]]

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You can do that as well. Just copy/paste the characteristic and change the parameters in the copy.

[[Ni...]]

LSQ - Average of all the points around the circle. Will give almost what a mic check gives.

Max inscribed - Will give the smallest circle it can find on IDs and ODs - Affected by roundness.

Min Circumscribed - Will give the biggest circle it can find on IDs and ODs - Affected by roundness.

You don't have to measure the same circle twice to report in both evaluations.
Just go on the characteristic tab. Open up three diameter checks. Pick the same feature on all three Diameter checks.
Then click on the feature and choose what evaluation you want. You can report all three evaluations this way without having to scan the same feature multiple times.

I also recommend changing the evaluation on the characteristic tabs and not the features tab. Because the feature tabs contains the nominal to where a perfect part should be.
You are only changing the evaluation for reporting purposes.
So change the evaluation on the characteristics tab inside the diameter check.

evaluations.PNG