Shape builder tool - Edges do not line up

[laurencer93489389]

I've set up 3 circles and cut the overlapping edges of 2 of the circles using the shape builder tool.

But when I zoom into the edge of the black circle the red and green circles edges do not line up perfectly with the edge of the black circle.

Please see the attached images.

Many thanks.

[Doug A Roberts]

How big are these shapes?

[laurencer93489389]

The black circle is 70mm

[laurencer93489389]

I'd zoomed in around 5000% I know that's a lot but even at 100%, I can see a halo effect on the edge of the green shape.

Maybe I'd be better to use a clipping mask.

[laurencer93489389]

Still hoping someone can help me with this query.

[Michael Bullo]

Could this have something to do with alignment to the pixel grid?