diff --git a/LuaLibs/ProcessDrill.lua b/LuaLibs/ProcessDrill.lua
index f797e40..e344bd3 100644
--- a/LuaLibs/ProcessDrill.lua
+++ b/LuaLibs/ProcessDrill.lua
@@ -594,8 +594,10 @@ function ProcessDrill.Make( Proc, nPhase, nRawId, nPartId, dCurrOvmH)
          local dHoleToCutDistance = vDistance[1]
          -- se il taglio accorcia realmente il foro
          if ( dHoleToCutDistance > 10 * GEO.EPS_SMALL or Proc.AffectedFaces.Right) and dHoleToCutDistance < dLen then
+            local dToolTipFromCenterDrill = ( ( dDiam / 2) - ( dToolDiam / 2))
+            local dExtraSicDistFromThToTiltedCut = sqrt( ( dToolTipFromCenterDrill / CosB)^2 - dToolTipFromCenterDrill^2) + sqrt( ( ( dDiamTh / 2) / CosB)^2 - (dDiamTh / 2)^2)
             dMaxDepth = dMaxDepthOri
-            dMaxElev = dLen - dHoleToCutDistance
+            dMaxElev = dLen - ( dHoleToCutDistance - dExtraSicDistFromThToTiltedCut)
             bTryDrill = true
             local dToolAddLength = dLen - dMaxElev
             -- se l'utensile è comunque troppo corto lavoro il massimo possibile