diff --git a/CurveComposite.cpp b/CurveComposite.cpp
index 8ab5d9d..b3342a5 100644
--- a/CurveComposite.cpp
+++ b/CurveComposite.cpp
@@ -1596,6 +1596,8 @@ CurveComposite::AddArcTg( const Point3d& ptNew, bool bEndOrStart)
   // verifico lo stato
    if ( m_nStatus != OK)
       return false ;
+  // recupero il versore normale al piano ( estrusione oppure se nulla asse Z locale)
+   Vector3d vtN = ( m_VtExtr.IsSmall() ? Z_AX : m_VtExtr) ;
   // costruisco l'arco (in casi articolari puņ essere una linea)
    PtrOwner<ICurve> pCrv ;
   // se da aggiungere alla fine
@@ -1604,7 +1606,7 @@ CurveComposite::AddArcTg( const Point3d& ptNew, bool bEndOrStart)
       GetEndPoint( ptEnd) ;
       Vector3d vtDir ;
       GetEndDir( vtDir) ;
-      pCrv.Set( GetArc2PVN( ptEnd, ptNew, vtDir, Z_AX)) ;
+      pCrv.Set( GetArc2PVN( ptEnd, ptNew, vtDir, vtN)) ;
       if ( IsNull( pCrv))
          return false ;
    }
@@ -1614,7 +1616,7 @@ CurveComposite::AddArcTg( const Point3d& ptNew, bool bEndOrStart)
       GetStartPoint( ptStart) ;
       Vector3d vtDir ;
       GetStartDir( vtDir) ;
-      pCrv.Set( GetArc2PVN( ptStart, ptNew, vtDir, Z_AX)) ;
+      pCrv.Set( GetArc2PVN( ptStart, ptNew, vtDir, vtN)) ;
       if ( IsNull( pCrv))
          return false ;
       pCrv->Invert() ;