On Sat, 31 Dec 2005 01:11:59 GMT, "David Anderson"
wrote:

How to get the best machined finish on aluminum casting? With my face mill,
I get a near mirror finish, but with internal boring bar, I get a terrible
finish, despite variations in tool geometry. A cutting fluid?
TIA, Dave

Yes, use a cutting fluid by all means. If the cutter gets gummed it
will produce a really awful finish.

Check for chatter. You may need a stiffer boring bar.