Looking for 90 deg. countersink to cut underside

[georgebarr]

I am looking for a way to countersink (90 degree) the underside (bottom side) of a 1/2" diameter hole in 6060 1" thick aluminum. I already have a countersink bit to cut the top side of a hole so that I do not have to worry about deburring the hole, but need to do the same to the bottom of the hole all without moving the stock that is mounted to my CNC mill table.

My question is, is there a special countersink to do this?

Thanks,

[ckirchen]

What is the OD of the backside's countersink? Large enough for a flat head cap screw or just enough to debur the edge?

[georgebarr]

I just need something to debur the edges, but want it to be done using the CNC machine that I have. If I have 100 holes, then I definately do not want to do this manually.

Thanks,

[Geof]

Use a 45 degree dovetail cutter, they are available in 1/2" diameter with a 3/8" shank. All you have to do is grind the head down a few thou to pass through your 1/2" hole and you still have enough over the shank diameter to do a 20 thou chamfer.

[ckirchen]

Geof beat me to the answer...

If your tool changer is full or you want to save a toolchange, I have used double angle cutters in the past with success. Mine were from Harvey Tool.