diff --git a/LuaLibs/WProcessLapJoint.lua b/LuaLibs/WProcessLapJoint.lua
index c2d86d0..8889c17 100644
--- a/LuaLibs/WProcessLapJoint.lua
+++ b/LuaLibs/WProcessLapJoint.lua
@@ -1947,7 +1947,7 @@ local function MakeSideGrooveByMill( Proc, nFacet, nRawId, b3Raw, sCustomMach, d
       local dMaxElev = dMaxMat
       local dStepOtherFace = 0
       local dDepthOtherFace = dMaxMat
-      if Proc.Fct == 2 and vtN2:getZ() < -0.99 and vtN2:getZ() > -1.01 then
+      if Proc.Fct == 2 and abs( vtN2:getZ()) > 0.99 and abs( vtN2:getZ()) < 1.01 then
          dStepOtherFace = dStepOri or EgtGetMachiningParam( MCH_MP.STEP)
          if dStepOtherFace < GEO.EPS_SMALL then dStepOtherFace = 0.75 * dMaxMat end
          local nStepOtherFace = ceil( ( dElevOtherFacet - dMaxMat) / dStepOtherFace)