Sensor that can detect metal through epdm rubber

Many pillar drills are fitted with an adustable depth stop specially for this purpose. It is usually a knurled threaded ring that goes up and down on a threaded shaft that has been machined to a D cross-section, with a measuring scale engraved on the flat face of the D.

And I would try a hall effect sensor to detect the metal. You could use the voltage out put to drive a LED bargraph to show depth.Try here www.allegromicro.com

Here is my problem, I have an aluminum profile specific block that holds the profile while it runs through the drill unit. The drill unit is a drill motor mounted in a block the rotates 360 degrees that causes the drill bit to puncture in the bulb of the profile, the bulb of the profile is rubber filled with air. I need to know if there is a sensor that will mount in the bottom of the guide block that will sense when the drill bit punctures the bulb which in turn gets closer to the drill block, but don't want to go through the back side of the bulb, because this will cause a water leak on the vehicle. Is there a sensor that can do this with out being affected by the static electricity of a coated rubber profile running across it at 70 fpm and have to detect the drill bit when drilling every 100 mm. If you can think of anything or know someone who might know of something let me know. My email address is thomas.sutton@maps-na.com

You could try an eddy current differential probe on the back side of the bulb, as drilling tool approximates, the probe will detect it, as well as if comes into contact with the back wall. You will need to "calibrate" the system with different drill depths, but it can be applied to your speed of 70fpm and must function.