Does anybody have any techniques to eliminate chip sticking/dragging during spot drilling gummy aluminum? (produces scratches around holes)
I almost always use 12mm Minimaster with 90 degree spot inserts for all my spot drilling and chamfering. I've tried the following parameters(all have a 3 revolution dwell at bottom)
1500 rpm @ 5 ipm
1500 rpm @ 12 ipm
6000 rpm @ 10 ipm
6000 rpm @ 45 ipm
The results for all the above are exactly the same, with the exception of speed, of course. The last is my favorite.
I have also tried pecking, but same results.
Normally, this isn't a problem since the scratches are light enough to be removed by the etching process before anodizing. However, I have a part that cannot be anodized and requires a cosmetic machined finish, and has a lot of little holes with required edge chamfers. Obviously, I cannot have these little scraches around the holes.
I hope to be able to spot/chamfer in one shot, then drill, and be done. (rather spot, drill, then chamfer)
Any advice on this matter is appreciated.