"Doc" wrote in message
ink.net...
| Looking for any tips/tricks for drilling a hole w/a drill press that's as
| close to dead-center to a specified point as possible.
|
| Here's what I've been doing - I have the position marked with graph paper
| that's taped to the workpiece. With the help of a magnifying glass, I
| painstakingly move the piece until the tip of the bit is aligned with the
| conjoining lines. By aligning with the tip I mean I view the tip both from
| the narrow or "pointy" persepective within the channel of the bit and then
| turn it 90 deg and look at the the wider perspective, and view it from the
| side and front to make sure I have it aligned with both the X and Y axis.
| When I finally get it so the tip is as centered as I can make it whichever
| way the bit is turned and in relation to both axis, I clamp the piece to
the
| plate of the drill press and drill the hole. However, on examination, the
| hole comes out obviously not dead center in relation to the graph paper
| lines.
|
| I've also tried aliging it with the drill running, going visually by where
| the "point" appears to be when the bit is spinning. I get somewhat better
| results this way but wonder if there's a more precise and dependable way
of
| achieving a centered hole.
|
| Thanks for any input.

Finding one of the optical center punches is the best way to locate the
center punch hole. After that, find the smallest drill bit your press will
handle and drill the hole with that, or at least a quarter of an inch or so.
The next thing is hardware you have to go look for. Double margin drill
bits. You work your way up using the previous hole size as the first
margin, or pilot bit. Not sure where to some, industrial supply, ebay,
aviation supply, or similar places.
I've also used what we call "core drills" which are special drill bits
made by turning down the first quarter of an inch or so of the drill bit to
the pilot hole you're working with, but obviously not too small. You still
have to sharpen the remaining edge of the bit. In doing this, I've started
with a center punch mark and worked my way up to a 0.3125" +/- .002" which
is even harder without the right tools.
By the way, double margin drill bits are awesome for drilling stainless!
I bought a bunch at Boeing surplus near Seattle and absolutely love using
them.