File: Part_Document_Scripts/Measure_Curve_With_3_PTS_AS_CIRCLE.py
Version: 1.1
Document Type: Part (also works with Part inside Product or Process)

Measures the effective radius and diameter of a curve by placing three points on it and fitting a circle through them. The result is displayed in a message box. All construction geometry is deleted after measurement.

See Measure Curve With 3 Points As Circle Keep Con to keep the construction geometry.

1. Open a CATPart document containing a curve to measure
2. Run the script
3. Select the curve to measure — click OK when done
4. A message box displays the result

A message box showing:

Radius: 25.43mm
Diameter: 50.86mm

All construction geometry (extracted curve, points, circle) is deleted after the result is shown.

1. The curve is extracted and converted to a datum
2. Three points are placed on the curve using extremum points (max X, Y, Z directions)
3. If the extremum points are coincident (large radius curves), points are placed at 20%, 50%, and 80% along the curve instead
4. A circle is fitted through the three points
5. The radius of the circle is measured and displayed

• The measurement is an approximation — accuracy depends on how circular the curve is
• Results are rounded to 2 decimal places
• For a surface radius measurement see Measure Radius Surface