bell-mouthed holes

[HuFlungDung]

I think you just need to 'train your fate'

Make up a sketch of a hole that is 1.08 on one side, and 1.065 on the exit. Think hard about "however shall I make that hole"......then recall your past experience with the spade drill and use that. Immediately, that drill will drill a nice straight hole no matter how you try to make it bellmouthed

[ctate2000]

Could be the tool holder and drill combination. I suspect the drill is pushing to one side while entring the cut because of the force. The point of a drill does not cut, it mkes the material flow away from center. The point therefore likes walk to one side causing the bell shape. Once you have the drill fully engaged it is supported and can no longer push to the side. Start slower and peck a couple of times during entry to relieve the force on the tool. Once you are at full diameter lean on it.

[snowshovelbmx]

yeah we ordered an 1 1/16 u drill... will not walk and will always drill onsize we hope..problem solved....or so they say. Thanks.

[davereagan]

Who makes the U drill? Also, has anyone ever gotten decent tool life running a TiALN cobalt Allied insert at the 250sfm in 1018 steel? It just seems way too fast.