I need to make a drill extension guide to finish a project. I want to use a
..090 end mill to manually peck drill a hole in angled face deep in the
cavity of a mold. I can get a shot at it with a long bit. I was thinking I
would make an 1/8 bit holder extensions six inches long to do the job. That
would probably be adequate in itself for this job, but I was thinking I get
get within a few thousandths and reduce risk of spin damage by running the
"extension" through a guide with one end machined to wrap around the
protrusion where the face I want to drill is located.

The thing is I don't have a lot of room to work. About .185 clearance on
one side of the extension from center. I could turn a piece of stock down
to .36 just fine, but then I would be limited in the main diameter of the
extension to about .25 or less.

I need about 6-7 inches of reach. I have some aircraft drills in
appropriate sizes, but my experience is that they tend to flex and wander
after more than an inch or two.

You know, I think I am just going to make the extension for now and get the
job done, but how would you tackle it the other way I described. Remember
there isn't much point if it doesn't start out big enough so one end can be
machined to set in place...