diff --git a/Drilling.cpp b/Drilling.cpp
index 3c1ddb0..a6a3dee 100644
--- a/Drilling.cpp
+++ b/Drilling.cpp
@@ -1395,7 +1395,7 @@ Drilling::GetHoleData( SelData Id, Hole& hole)
       hole.bBlind = false ;
    // altrimenti determino la distanza del fondo del foro dal bordo opposto del grezzo
    else {
-      const double BLIND_TOL = 20 ;
+      const double BLIND_TOL = 10 ;
       double dBackElev ;
       if ( GetElevation( m_nPhase, hole.ptIni, - hole.vtDir, dBackElev)  &&  ( dBackElev - hole.dThick) <= BLIND_TOL)
          hole.bBlind = false ;