I am looking to purchase some small 2 flute counterbores to be used on class 3 copper. They are going to be used for socket head cap screws. The 3 fluted ones don't work very good. Weldon makes 2 fluted ones but they are not cheap. they are around $50 plus dollars a piece. The sizes can range from #8's up to 3/8. A guy I work with has the Weldon ones that he got from a previous employer and they seem to work really well on the class 3 copper. This will be done on a drill press.