Radius measurement with small arc

[[Da...]]

Hi everyone,

I need to measure a radius on a component that has a reduced arc (the central angle of the arc is 96°). I was thinking of using a 2D curve and then use line profile to obtain the minimum and maximum points of the surface and verify that both are within the tolerance range 0 to -0.05.. Could this be a good strategy? 

Another approach could be to measure a good number of points along the arc and create the perpendicular to the center of the theoretical circle.

 

[[Ma...]]

Curve is a good option if you have it.

If you have unstable results, then i would use few points rather than scan.

Do you want to measure that R50 or pitch circle?

[[Da...]]

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I need to measure the outer radius highlighted in yellow.

[[Ma...]]

For that cylindricity you would need to scan it.

I saw on forum to use restricted radius to obtain origin, then they used this origin in nominal, restrict origin and allow radius to obtain measured radius, but i wouldn't sign under that.

I would rather measure as second cylinder with 3 circlular paths and 7 points per path - point measurement, not scanning.

[[Pa...]]

For evaluation of the size of that radius, I would constrain the X/Z locations (or whatever axes makes sense in your application).  For evaluation of the location, I'd constrain the radius for size.  I'd use discrete points for both of these; I like Martin's suggestion of 7 points per circle.

For cylindricity I'd go back in and scan three partial circles minimum in a cylinder strategy.  I'd constrain nothing for this evaluation, though for a very short cylinder it may make sense to constrain normal vector.

I get repeatable results, though I (like Martin) do not claim to know what will produce "the correct" result.