Measuring a small arc segment.

[SingularitY]

When measuring a small arc segment, what are your preferred methods?
The reason why I ask, is because I usually use a high point density scan and construct a circle There is a program I am rewriting that used a method I'm not sure is proper. He took 4 points on the arc, constructed a circle, dimensioned profile of a line, took the measured value and added it to the nominal diameter, then dimensioned the radius using a generic feature. I understand the mind state, I'm just not sure if it is proper. I've heard about using "fixed radius" auto features but I haven't used it yet.
As always, your opinion is always appreciated.

[dph51]

From James Mannes

At a recent users group meeting this topic was discussed and the following steps were given to achieve both the location and diameter of a small arc/radius

To measure a partial arc/radius:


1. create a "measured" circle
2. edit (F9) the circle and add additional hits and edit the "best fit math type" to "FIXED Radius", edit the NOMINAL DIAMETER, check box to "regenerate hits", when prompted "equal spacing" answer YES
3. ctrl E the feature to execute it and re-capture the measured hit points
4. dimension the "location only" of the fixed radius circle/arc
5. edit dimension tol's to print
6. create an alignment and set origin on fixed radius circle
7. (if using CAD skip this step) F10/Parameters>Probing> enable polar compensation for the active workplane
8. with joystick measure more individual/separate points on arc radius (if using CAD use "vector point" skipping step #7)
9. dimension individual points using the "PR" polar radius function
10. F10/Parameters>Probing> turn off or disable polar compensation
__________________
Checking radii was discussed in the basic class I attended. In my notes the instructor recommended using FIXED RAD if the radii location is critical and MIN SEP if the radii size is critical.

[SingularitY]

I've never used either method, but I will give it a shot to see how repeatable it is. Thanks!
So I take it the profile method I described earlier isn't proper? (I'm asking because I'm trying to show that the old program is incorrect.)