Countersink depth control on CNC

I am looking at making many 1.5" holes with a countersink 1/2" deep in large steel plate. The depth tolerance of the countersink is
critical. The plate varies in thickness and can be slightly bowed. How do I control the depth of the countersink on a CNC machine? I can't just go to the same Z position every time. The plate is too big to probe every location and correct for depth, or at least I don't want to take the time to do it. I found a spring loaded tool on the web but it is too small.
Any ideas or tools I don't know about????
Thanks in advance. Any constructive replies are appreciated.
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I guess it really depends on what your expertise level is and the flexibility of the machine.
1. Make your own spring loaded tool. 2. Add a probe of some type next to the countersink, and do each countersink as a probing operation. (Microswitch on a stick?) 3. Do a probing operation first as a complete program for the whole plate at each hole location.
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On Wed, 24 Oct 2012 18:22:44 -0700, Bob La Londe wrote:

I'm not a CNC guy, but for 1 & 2, make sure you're not riding on a chip, and for 3, make sure that the bows & ripples of the plate don't change from the time you probe to the time you countersink.
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On 10/24/2012 5:50 PM, snipped-for-privacy@yahoo.com wrote:

I assume you know about these type countersinks:
http://www.2linc.com/countersink_depth_stop.htm
One brand is Severance and are called Micro-stop countersinks.
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    It would work with springy workpieces which need to be clamped down to a stable level support (the "slightly bowed" ones), but not for variations in thickness -- unless the CNC machine is also fitted with a spring-loaded shank. I've got a couple of the Severance ones in drill-press size, and like them for constant depth, but I don't think that they would work well in what is described as the problem.
    Hmm ... maybe this has the spring give in the shank, and thus might well do the job. Those springs look serious.
    Good Luck,         DoN.
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