Hey all. I need some advice in the worst way. First off, this is a new problem that has developed on some parts we run all the time. The material is aluminum. We are drilling and tapping around 30 holes, m5 x .8 and 1/2" thread depth. Our problem is all the sudden over the past couple of weeks, we will have a random hole or two or three out of 30 that the no go gauge goes in to. We can run 200 holes with no problems and then all the sudden 1 or 2 bad holes pop up. We have tried different RPM and feedrates with no succes. Different taps and drills as well. . We are running these on Haas VF4 machines and have the same issue on more than one machine. I have even tried it on my old VF2 and it will still get a bad hole once in a while. A bad hole scraps that part and the material alone is quite costly. I am using rigid tapping with the tap and have tried different collet holders to make sure the holder is not running out. I am about at my wits end. Anyone have any suggestions?? Thanks all.