diff --git a/CurveArc.cpp b/CurveArc.cpp
index 55ea883..101a954 100644
--- a/CurveArc.cpp
+++ b/CurveArc.cpp
@@ -640,7 +640,8 @@ CurveArc::Save( NgeWriter& ngeOut) const
    if ( ! ngeOut.WriteVector( m_VtS, ";"))
       return false ;
   // angolo al centro
-   if ( ! ngeOut.WriteDouble( m_dAngCenDeg, ";"))
+   int nDec = ( m_dRad < 0.1 * BIG_ARC_RAD ? 6 : 9) ;
+   if ( ! ngeOut.WriteDouble( m_dAngCenDeg, ";", false, nDec))
       return false ;
   // deltaN
    if ( ! ngeOut.WriteDouble( m_dDeltaN, ";", true))
@@ -673,6 +674,7 @@ CurveArc::Load( NgeReader& ngeIn)
   // recupero il versore iniziale
    if ( ! ngeIn.ReadVector( m_VtS, ";"))
       return false ;
+   m_VtS.Normalize() ;     // per garantire la precisione con raggi grandi
   // recupero l'angolo al centro
    if ( ! ngeIn.ReadDouble( m_dAngCenDeg, ";"))
       return false ;
@@ -766,7 +768,8 @@ CurveArc::Validate( void)
      // eseguo il controllo
       m_nStatus = ( ( m_VtN.IsNormalized()  &&  m_VtS.IsNormalized()  &&
                     AreOrthoApprox( m_VtN, m_VtS)  &&
-                    m_dRad > EPS_SMALL  &&  fabs( m_dAngCenDeg) > EPS_ANG_ZERO) ? OK : ERR) ;
+                    m_dRad > EPS_SMALL  &&  m_dRad < MAX_ARC_RAD  &&
+                    fabs( m_dAngCenDeg) > EPS_ANG_ZERO) ? OK : ERR) ;
    }
 
    return ( m_nStatus == OK) ;
diff --git a/EgtGeomKernel.rc b/EgtGeomKernel.rc
index a677cd9..3b1dfb6 100644
Binary files a/EgtGeomKernel.rc and b/EgtGeomKernel.rc differ
diff --git a/GeoConst.h b/GeoConst.h
index 6444832..30c8a3f 100644
--- a/GeoConst.h
+++ b/GeoConst.h
@@ -37,6 +37,12 @@ const double LIN_TOL_FINE = 0.01 ;
 // lunghezza minima feature lineare
 const double LIN_FEA_LEN_STD = 20 ;
 
+//----------------- Costanti per archi ---------------------------------------
+// raggio oltre il quale un angolo al centro EPS_ANG_ZERO produce spostamento maggiore di EPS_SMALL
+const double BIG_ARC_RAD = 500000 ;
+// raggio massimo ammesso per un arco
+const double MAX_ARC_RAD = 50000000 ;
+
 //----------------- Costanti per archi come curve di Bezier ------------------
 // massimo angolo al centro di un arco espresso tramite curva di Bezier
 const double BEZARC_ANG_CEN_MAX = 90 ;
diff --git a/Vector3d.cpp b/Vector3d.cpp
index c50a26b..9dac16c 100644
--- a/Vector3d.cpp
+++ b/Vector3d.cpp
@@ -151,7 +151,7 @@ Vector3d::Normalize( double dEps)
 {
   // se già normalizzato, ok
    double dSqLen = x * x + y * y + z * z ;
-   if ( fabs( 1.0 - dSqLen) < ( 2 * EPS_ZERO))
+   if ( fabs( 1.0 - dSqLen) < ( 2 * 1000 * DBL_EPSILON))
       return true ;
 
   // se troppo piccolo, errore