diff --git a/VolZmapVolume.cpp b/VolZmapVolume.cpp
index 73740ee..b306385 100644
--- a/VolZmapVolume.cpp
+++ b/VolZmapVolume.cpp
@@ -2009,6 +2009,8 @@ VolZmap::Comp_5AxisMilling( int nGrid, const Point3d& ptS, const Point3d& ptE, c
                 vPtCtrlLoc[p].ToLoc( vSurfBez[nSurfInd].frYMainDim) ;
             vSurfBez[nSurfInd].bbSurfY.Add( vPtCtrlLoc) ;
         }
+
+        ++ nSurfInd ;
     }
 
    // scorro tutti gli spilloni interessati
@@ -2423,7 +2425,7 @@ VolZmap::MillingGeneralMotionStep( const Point3d& ptPs, const Vector3d& vtDs, co
       InitializePointsAndVectors( ptSti, ptEni, vtDSi, vtDEi, ptLs, ptLe, vtLs, vtLe) ;
 
       // Standard è multithread
-      constexpr bool MULTITHREAD = false ;
+      constexpr bool MULTITHREAD = true ;
       if ( MULTITHREAD) {
          // Ciclo sulle mappe
          vector<future<bool>> vRes( m_nMapNum) ;