diff --git a/SurfFinishing.cpp b/SurfFinishing.cpp
index e5bd68e..cc26225 100644
--- a/SurfFinishing.cpp
+++ b/SurfFinishing.cpp
@@ -1406,7 +1406,7 @@ SurfFinishing::UpdateFrameAndToolDir( int nAuxId, bool& bRecalc)
    bRecalc = true ;
    Frame3d FrOld = m_Frame ;
 
-  // se lavorazione con superficie
+  // se lavorazione con regione
    if ( m_Params.m_nSubType == SURFFIN_SUB_ZIGZAG  ||  m_Params.m_nSubType == SURFFIN_SUB_ONEWAY  ||
         m_Params.m_nSubType == SURFFIN_SUB_SPIRALIN  ||  m_Params.m_nSubType == SURFFIN_SUB_SPIRALOUT  ||
         m_Params.m_nSubType == SURFFIN_SUB_Z_CONST  ||  m_Params.m_nSubType == SURFFIN_SUB_OPTIMAL  ||
@@ -1414,7 +1414,7 @@ SurfFinishing::UpdateFrameAndToolDir( int nAuxId, bool& bRecalc)
       PtrOwner<ISurfFlatRegion> pSfr( nullptr) ;
       int nPathId = m_pGeomDB->GetFirstGroupInGroup( nAuxId) ;
       while ( nPathId != GDB_ID_NULL) {
-        // recupero la superficie
+        // recupero la regione
          int nSfrId = m_pGeomDB->GetFirstInGroup( nPathId) ;
          if ( m_pGeomDB->GetGeoType( nSfrId) != SRF_FLATRGN)
             return false ;
@@ -1484,7 +1484,7 @@ SurfFinishing::UpdateFrameAndToolDir( int nAuxId, bool& bRecalc)
          Frame3d frLoc ;
          if ( ! frLoc.Set( ptCentroid, vtExtrusion))
             return false ;
-        // recupero la PolyLine assocuata alla prima curva in locale al frame creato
+        // recupero la PolyLine associata alla prima curva in locale al frame creato
          PolyLine PLLoc ;
          if ( IsNull( vCrv[0])  ||  ! vCrv[0]->IsValid()  ||
               ! vCrv[0]->ApproxWithLines( EPS_SMALL, EPS_ANG_ZERO, ICurve::APL_SPECIAL, PLLoc)  ||
@@ -1495,6 +1495,12 @@ SurfFinishing::UpdateFrameAndToolDir( int nAuxId, bool& bRecalc)
          double dDimX, dDimY ;
          if ( ! PLLoc.GetMinAreaRectangleXY( ptFrCenter, vtFrX, dDimX, dDimY))
             return false ;
+        // oriento il frame in modo opportuno rispetto all'asse X
+         if ( vtFrX.x < - SQRT1_2)
+            vtFrX.Invert() ;
+         else if ( abs( vtFrX.x) < SQRT1_2  &&  vtFrX.y < - SQRT1_2)
+            vtFrX.Invert() ;
+        // definisco il frame
          ptFrCenter.ToGlob( frLoc) ;
          vtFrX.ToGlob( frLoc) ;
          if ( ! m_Frame.Set( ptFrCenter, vtExtrusion, vtFrX))