diff --git a/CAvSilhouetteSurfTm.cpp b/CAvSilhouetteSurfTm.cpp
index fa7f19c..f3992ba 100644
--- a/CAvSilhouetteSurfTm.cpp
+++ b/CAvSilhouetteSurfTm.cpp
@@ -1019,7 +1019,7 @@ CAvParSilhouettesSurfTm::Prepare( void)
    m_dDimZ = b3All.GetDimZ() ;
 
   // set utensile corrente per calcolo delle collisioni
-   double dExtraXY = m_dRad ;
+   double dExtraXY = m_dRad + m_dOffsR ;
    if ( m_dSideAng < EPS_ANG_SMALL)
       m_cavTstm.SetStdTool( m_dDimZ + m_dOffsR, m_dRad + m_dOffsR, m_dCornRad + m_dOffsR) ;
    else {
@@ -1037,7 +1037,7 @@ CAvParSilhouettesSurfTm::Prepare( void)
 
       double dStemRad = m_dRad + dDeltaRad ;
       double dTipRad = m_dRad ;
-      dExtraXY = dStemRad ;
+      dExtraXY = dStemRad + m_dOffsR ;
       m_cavTstm.SetAdvTool( m_dDimZ + m_dOffsR, dStemRad + m_dOffsR, m_dMaxMat, dTipRad + m_dOffsR, m_dCornRad + m_dOffsR) ;
    }