diff --git a/VolZmapVolume.cpp b/VolZmapVolume.cpp
index cf9dc5f..3bee515 100644
--- a/VolZmapVolume.cpp
+++ b/VolZmapVolume.cpp
@@ -2774,8 +2774,11 @@ VolZmap::Conus_XYMilling( unsigned int nGrid, const Point3d & ptS, const Point3d
 bool
 VolZmap::CylBall_Drilling( unsigned int nGrid, const Point3d & ptS, const Point3d & ptE, const Vector3d & vtToolDir)
 {
-   double dStemHeigth = m_Tool.GetHeigth() - m_Tool.GetRadius() ;
- 
+   double dStemHeigth = m_Tool.GetHeigth() ;
+  // Sfera
+   if ( m_Tool.GetType() == Tool::BALLMILL)
+      dStemHeigth -= m_Tool.GetRadius() ;
+
    CompCyl_Drilling( nGrid, ptS, ptE, vtToolDir, dStemHeigth, m_Tool.GetRadius(), false, false) ;
 
   // Sfera
@@ -2791,7 +2794,10 @@ VolZmap::CylBall_Drilling( unsigned int nGrid, const Point3d & ptS, const Point3
 bool
 VolZmap::CylBall_Milling( unsigned int nGrid, const Point3d & ptS, const Point3d & ptE, const Vector3d & vtToolDir)
 {
-   double dStemHeigth = m_Tool.GetHeigth() - m_Tool.GetTipHeigth() ;
+   double dStemHeigth = m_Tool.GetHeigth() ;
+  // Sfera
+   if ( m_Tool.GetType() == Tool::BALLMILL)
+      dStemHeigth -= m_Tool.GetRadius() ;
  
    CompCyl_Milling( nGrid, ptS, ptE, vtToolDir, dStemHeigth, m_Tool.GetRadius(), false, false) ;