Just trying to figure this out - when I dimension a circular feature I'll get one size but when adding a GD&T dimension for that same exact feature I get a different size altogether (example below). What's the reason for this?
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.
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.
