Look at my post on 5-15-2009 above. If you change parameter 5006.6 to 0 this sets tool length compensation to happen on the next axis movement. Prior to changing this parameter as soon as it read G49 it wanted to move Z by the tool length. I do not know if this works on all fanuc controls but my post is set that when it cancels the height offset as in the code above, it calls the H offset right after canceling or changing the G5.1 settings. By doing this there is no axis movement and no crash. Prior to changing parameter 5006.6 we crashed our share of toolholders/parts. Hope this helps

Hi, This is my first post so bear with me.I just went through this with my Fanuc 21i. If you change parameter 5006.6 to 0 this sets tool length compensation to happen on the next axis movment. By changing this parameter you can change the precision of your high speed look ahead using the same tool for chamfering holes (drill cycle) then edges with a chamfering tool (contour)(Ex. Q2 to Q5) (my machine uses G5.1 Q1 to turn on and G5.1 Q0 to turn off look ahead with M300 Q1 thru Q5 to set precision) . Or when you may want to rough & finish surfaces with the same ball mill. This way when you cancel tool length compensation G49 then change the M300Q1 thru M300Q5 value of G5.1 (or turn it on as with the chamfer tool) before the next move call up G43 again (none of these are axis moves). Hope this helps. If it does not make sense maybe one of the post or control gurus can chime in.