Boolean union fail why and need 0.03 fillet

Hi,
v5

Can someone add a 0.03 inch fillet where shown please
after managing to boolean union this !

G upper to blue, G lower works ok.

It worked earlier then I redid the 0.25 fillet and now it fails. yet intersect shows as ok.
BooleanUnion fail on G to rest.3dm (474.0 KB)

Cheers
Steve

fillet here?

I’d use filletsrf and then close up the missing bit manually.

with the info you provided, I’d go after it something like this

the surface on the left is a patch (v9)

Boolean union won’t work with your pieces (in V5, haven’t tried others), but instead you can use each piece to trim away the internal surfaces of the other and then join the results: that does work.

Edit: Boolean works in R8.