I need to drill some fairly accurate holes at an angle through some
aluminum square tubing (or whatever you call tubing that's square
instead of round).

I guess the main problem is that my cheap drill press has some play
in it so that the bit doesn't necessarily follow the intended path
straight down. So when I put the metal at an angle, the bit is going
to move towards the deeper side as it drills into the metal.

.... should I use something to press on the spinning chuck shaft so
that it drills closer to correct?

.... if I were to drill straight down through the aluminum with a
smaller diameter bit, when the aluminum is angled will the larger
drill bit end up going through the center of that hole? (Yes, this
is easy enough to test)

.... is there some trick I don't know about?

Thank you.

John Doe wrote:

I need to drill some fairly accurate holes at an angle through some
aluminum square tubing (or whatever you call tubing that's square
instead of round).

I guess the main problem is that my cheap drill press has some play
in it so that the bit doesn't necessarily follow the intended path
straight down. So when I put the metal at an angle, the bit is going
to move towards the deeper side as it drills into the metal.

... should I use something to press on the spinning chuck shaft so
that it drills closer to correct?

... if I were to drill straight down through the aluminum with a
smaller diameter bit, when the aluminum is angled will the larger
drill bit end up going through the center of that hole? (Yes, this
is easy enough to test)

... is there some trick I don't know about?

Thank you.


You may be able to get close enough using a drill guide. No matter
what, guide hole or not, you're going to have a problem with the drill
generating side force and deflecting away from the hole. Someone
smarter than me will answer, and I'll learn something.

In the mean time, I would do this with a square-face (NOT ball-end) end
mill in a nice rigid machine like a mill/drill or a real milling machine
-- not a cruddy old drill press.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

John Doe wrote:
I need to drill some fairly accurate holes at an angle through some
aluminum square tubing (or whatever you call tubing that's square
instead of round).

I guess the main problem is that my cheap drill press has some play
in it so that the bit doesn't necessarily follow the intended path
straight down. So when I put the metal at an angle, the bit is going
to move towards the deeper side as it drills into the metal.




You can first come in with an endmill to make a flat.

Then come in with a centering drill and drill an accurately located
hole. It will not deflect because it is on the flat.

"Polymer Man" wrote: (clip)Then come in with a centering drill and drill an
accurately located hole. It will not deflect because it is on the flat.
^^^^^^^^^^^^^^^
Yeah, but OP said he had to drill THROUGH the tubing. Your method will get
the drill started okay, but what happens when it gets to the other tubing
wall from the inside?

I guess he could lay out the "exit point" very accurately and come in from
the other direction using your method.

On Mon, 20 Feb 2006 21:11:40 GMT, John Doe
wrote:

I need to drill some fairly accurate holes at an angle through some
aluminum square tubing (or whatever you call tubing that's square
instead of round).

I guess the main problem is that my cheap drill press has some play
in it so that the bit doesn't necessarily follow the intended path
straight down. So when I put the metal at an angle, the bit is going
to move towards the deeper side as it drills into the metal.

... should I use something to press on the spinning chuck shaft so
that it drills closer to correct?

... if I were to drill straight down through the aluminum with a
smaller diameter bit, when the aluminum is angled will the larger
drill bit end up going through the center of that hole? (Yes, this
is easy enough to test)

... is there some trick I don't know about?

Thank you.






Since you need accurate hole location, and all you have is a drill
press, then you need to make a drill fixture. Depending on the number
of holes you could make it out of aluminum. If you need to do lots of
holes then aluminum could still be used but you would need to buy a
couple drill bushings. They are pretty cheap, and harder, lots harder,
than your drill. I don't know what tools you have or how handy you are
but here's a couple suggestions. Make a box, by bolting 1/2" plate
together, that slips over the tube with little clearance. Drill and
tap a hole for a screw to hold your part in the fixture box, so that
it can't shift while drilling. Set this box up at the angle you want.
Grind a flat where the drill will enter, drill first with a center
drill, then an undersize drill, then ream or drill with the final size
drill. Turn over the fixture and repeat. Then you can drill through
from the outside for each hole. This all requires careful layout. If
you need the drill bushings then order them and the reamer for them at
the same time. To support your fixture you could make an angled
support out of MDF. This would cradle the fixture at the correct
angle, is very repeatable, and would allow turning over the fixture
fast. You can put a dowell into the MDF to locate the fixture the same
each time. If you have only a couple parts to do then the whole thing
could be made of wood. If only 1 part then clamp some MDF to the part,
grind a flat so the drill starts easily, drill undersize, then the
final size. The MDF is dense enough and hard enough to act as a drill
bushing for a hole or two into aluminum. Good luck!
ERS

On Mon, 20 Feb 2006 21:11:40 GMT, John Doe
wrote:

I need to drill some fairly accurate holes at an angle through some
aluminum square tubing (or whatever you call tubing that's square
instead of round).

I guess the main problem is that my cheap drill press has some play
in it so that the bit doesn't necessarily follow the intended path
straight down. So when I put the metal at an angle, the bit is going
to move towards the deeper side as it drills into the metal.

... should I use something to press on the spinning chuck shaft so
that it drills closer to correct?

... if I were to drill straight down through the aluminum with a
smaller diameter bit, when the aluminum is angled will the larger
drill bit end up going through the center of that hole? (Yes, this
is easy enough to test)

... is there some trick I don't know about?

Thank you.

Hey John D.,

Best to create a "flat" with an end-mill in the drill chuck for the
drill to at least get started in, and better if you can make the
end-mill go right through the first side. Even a ground off to flat
ended drill bit will work in a pinch. It will be fairly straight. If
you can't do that, then lay the material flat and get a dimple drilled
at least to help. Bit of practice won't hurt.
You don't say how steep this "angle" is, or whether the tube is
straight and is it open ended, or how many of these holes you need to
make. If it is open and straight, you could get a piece of wood (at
least for a test) that is a fairly snug fit inside the tube, and
drill VERY easily through that, and when the drill bit touches the
"far side", just go in little pecks to lessen the deflection. Or even
the "flat ended" drill bit trick again, in lieu of an end-mill.

The larger the drill bit, the less deflection you should have, so
don't use a "small" bit first. If you've got more than a couple of
holes to do, use hardwood.

If you want to get elaborate, drill straight through a piece of steel,
say 1" stuff, then hacksaw the steel off through the hole so that you
have created a drill guide of the desired angle to clamp to the
outside of the aluminum to help guide the drill bit through, then
through the wood inside. One other thing that the wood inside does,
if it is tight enough, is help eliminate the burr inside too.

Take care.

Brian Lawson,
Bothwell, Ontario.

If you only have a few holes to drill, you can use a small drill and
start a hole perpendicular to the tube. Don't drill it very deep. Now
use a countersink on the hole. Now try a small drill at the angle you
want. Followed by the full sized drill. Don't drill through the other
side.

Repeat the above for the other side.

I am assuming that you don't have a end mill and that you do have a
countersink.

This will not be super accurate, but better than trying to just drill
at an angle.

Dan