[MMZ_TimeLord]

Those bits are High Speed Steel and are fine for copper IF they are sharp.

To keep them from "wandering", like small bits will tend to do, use a center punch to "dimple" the middle of your guide circles. This will give the bit a place to start cutting and minimize the "wandering".

I didn't have to do that on the block pictures I posted last night, because they are ¼ inch in diameter and tend to be pretty rigid. Anything smaller than that and I do "dimple" first.

The ball endmill I used for the seal channel is only 1/16 inch indiameter... BUT, it's only about ½ inch long so there is VERY LITTLE tendency to "wander"... also, I was cutting at 2500 RPM.