diff --git a/MachMgr.h b/MachMgr.h
index bdee15b..e20eb49 100644
--- a/MachMgr.h
+++ b/MachMgr.h
@@ -304,6 +304,7 @@ class MachMgr : public IMachMgr
       bool RemoveMachiningPreview( void) override ;
       bool MachiningApply( bool bRecalc, bool bPostApply = true) override ;
       bool MachiningUpdate( bool bPostApply = true) override ;
+      bool ChangePreviewMachiningToolShow( int nLookFlag) override ;
       bool PreparePreviewMachiningTool( void) const override ;
       bool RemovePreviewMachiningTool( void) const override ;
       int  GetPreviewMachiningToolStepCount( void) const override ; 
diff --git a/MachMgrOperations.cpp b/MachMgrOperations.cpp
index a4b68da..151020d 100644
--- a/MachMgrOperations.cpp
+++ b/MachMgrOperations.cpp
@@ -1106,6 +1106,22 @@ MachMgr::MachiningUpdate( bool bPostApply)
    return pMch->Update( bPostApply) ;
 }
 
+//----------------------------------------------------------------------------
+bool
+MachMgr::ChangePreviewMachiningToolShow( int nLookFlag)
+{
+  // recupero la lavorazione corrente
+   int nCurrMchId = GetCurrMachining() ;
+   if ( nCurrMchId == GDB_ID_NULL)
+      return false ;
+  // ne recupero il gestore
+   Machining* pMch = GetMachining( m_pGeomDB->GetUserObj( nCurrMchId)) ;
+   if ( pMch == nullptr)
+      return false ;
+  // eseguo
+   return pMch->ChangeToolPreviewShow( nLookFlag) ;
+}
+
 //----------------------------------------------------------------------------
 bool
 MachMgr::PreparePreviewMachiningTool( void) const