hi BurrMan

Many thanks
it works fine

Détail :

1 - Select Pomarańczowy surface
2 - Delete Pomarańczowy surface
3 - Select Joint srf
4 - Separate Joint srf to obtain 6 surfaces
5 - Select 26 Edges
6 - Delete 26 Edges
7 - Select 6 Surfaces
8 - Joint to make a solid

 

but i dont understand why deleting 26 edges erase the hole on the surfaces ?

here a gif

Chri