GD&T "size" always different from dimension "size"

you need to change the DEFAULT to LEAST SQUARES under FEATURE_MATH

Presuming you are in GeoTol (since you don't have datum shift showing), Y14.5 since 2009 requires the use of Constrained Least Squares for mathematical definition, where when you measure it, you had Least Squares selected.

The solution for Least Squares could be inside the material of the part.
Constrained Least Squares will never have any points lying inside the solution.

If the hole is shaped like an egg, your this may make a circle that least squares has part of the circle in space, and some in the metal, because a circle is round where an egg isn't. That size pin will not go through the hole.
Constrained least squares will make a circle and adjust size until none of the circle is in the metal (that's the constrained part). The CL2 solution, that size pin SHOULD go through the hole.
*caveat that you have to have hit the smallest part of the hole for this to work. If you took four hits, don't count on the pin thing working for you.

Well, you are checking an OD not a hole, so replace pin with ring gage. Same concept though.

{"data-align":"none","data-size":"full","title":"PICX1.jpg","data-attachmentid":532211}

you need to change the DEFAULT to LEAST SQUARES under FEATURE_MATH

Thank you! Is there a way to change the default math to least squares?

If in GEOTOL in the 'Reporting' Tab there is a dropdown list in the 'MATH' section

hey no sweat. its a good question.

i'd like to add to this question.
I understand going from DEFAULT to LSQ and getting different results for Diameters.

But how does the going from DEFAULT to LSQ on FEATURE MATH work?
What is DEFAULT doing? If I have a best fit bolt pattern what MATH do I want?




Is it just recalculating the TP based on the diameter since the LSQ and the DEFAULT (MAX_INSC) have slightly different center locations?

I believe the default is set same as the "SA" toggle when using a size dimension FCF, double check me by adding in a size dimension, tabbing over to ISO from ASME and click SA when tolerancing the size.

Should report the same size as the diameter shown in a TP or any callout that allows the reporting of a diametrical size.

Press F5 (or F10, I don't recall) and change the default through the Geometric Tolerance tab.

​

​