diff --git a/IntersLineCyl.cpp b/IntersLineCyl.cpp
index 425e094..ae40e16 100644
--- a/IntersLineCyl.cpp
+++ b/IntersLineCyl.cpp
@@ -60,14 +60,14 @@ IntersLineCyl( const Point3d& ptP, const Vector3d& vtV, double dH, double dRad,
 
    // Se la linea interseca entrambe le basi, si sono trovate le due intersezioni
    if ( nBasInt == 3) {
-      if ( isfinite( dU1) &&  isfinite(dU2)  &&  dU1 > dU2) {
+      if ( dU1 > dU2) {
          swap( dU1, dU2) ;
          swap( ptInt1, ptInt2) ;
          swap( vtN1, vtN2) ;
-         if ( bInvertNormals) {
-            vtN1 *= - 1 ;
-            vtN2 *= - 1 ;
-         }
+      }
+      if ( bInvertNormals) {
+         vtN1 *= - 1 ;
+         vtN2 *= - 1 ;
       }
       // Trovate intersezioni
       return true ;
@@ -119,10 +119,10 @@ IntersLineCyl( const Point3d& ptP, const Vector3d& vtV, double dH, double dRad,
          swap( dU1, dU2) ;
          swap( ptInt1, ptInt2) ;
          swap( vtN1, vtN2) ;
-         if ( bInvertNormals) {
-            vtN1 *= - 1 ;
-            vtN2 *= - 1 ;
-         }
+      }
+      if ( bInvertNormals) {
+         vtN1 *= - 1 ;
+         vtN2 *= - 1 ;
       }
       // Trovate intersezioni
       return true ;
@@ -155,10 +155,10 @@ IntersLineCyl( const Point3d& ptP, const Vector3d& vtV, double dH, double dRad,
          swap( dU1, dU2) ;
          swap( ptInt1, ptInt2) ;
          swap( vtN1, vtN2) ;
-         if ( bInvertNormals) {
-            vtN1 *= - 1 ;
-            vtN2 *= - 1 ;
-         }
+      }
+      if ( bInvertNormals) {
+         vtN1 *= - 1 ;
+         vtN2 *= - 1 ;
       }
       // Trovate intersezioni
       return true ;
diff --git a/VolZmapOffset.cpp b/VolZmapOffset.cpp
index 1aaf040..ebe88e6 100644
--- a/VolZmapOffset.cpp
+++ b/VolZmapOffset.cpp
@@ -971,11 +971,11 @@ VolZmap::CreateOffsetCylinderOnEdge( const Point3d& ptP1, const Point3d& ptP2, d
          Vector3d vtN1, vtN2 ;
          double dU1, dU2 ;
          if ( IntersLineCyl( ptC, Z_AX, CylFrame, dH, abs( dOffs), true, true,
-                             dU1, ptInt1, vtN1, dU2, ptInt2, vtN2)) {
+                             dU1, ptInt1, vtN1, dU2, ptInt2, vtN2, false, false)) {
             if ( dOffs > 0.)
-               AddIntervalsForOffset( nGrid, i, j, ptInt1.z, ptInt2.z, -vtN1, -vtN2, nTool, nTool) ;
+               AddIntervalsForOffset( nGrid, i, j, ptInt1.z, ptInt2.z, vtN1, vtN2, nTool, nTool) ;
             else
-               SubtractIntervalsForOffset( nGrid, i, j, ptInt1.z, ptInt2.z, vtN1, vtN2, nTool) ;
+               SubtractIntervalsForOffset( nGrid, i, j, ptInt1.z, ptInt2.z, -vtN1, -vtN2, nTool) ;
          }
       }
    }
diff --git a/VolZmapVolume.cpp b/VolZmapVolume.cpp
index c5f9dbf..0f238e3 100644
--- a/VolZmapVolume.cpp
+++ b/VolZmapVolume.cpp
@@ -6251,7 +6251,7 @@ VolZmap::CompCyl_Drilling( int nGrid, const Point3d& ptS, const Point3d& ptE, co
          Point3d ptInt1, ptInt2 ;
          Vector3d vtN1, vtN2 ;
          double dU1, dU2 ;
-         if ( IntersLineCyl( ptC, Z_AX, CylFrame, dH, dRad, bTapB, bTapT, dU1, ptInt1, vtN1, dU2, ptInt2, vtN2)) {
+         if ( IntersLineCyl( ptC, Z_AX, CylFrame, dH, dRad, bTapB, bTapT, dU1, ptInt1, vtN1, dU2, ptInt2, vtN2, false, true)) {
             SubtractIntervals( nGrid, i, j, ptInt1.z, ptInt2.z, vtN1, vtN2, nToolNum) ;
          }
       }