DIYbanter - View Single Post - Drilling a Straight Hole (Overhead, Into Concrete)

Smitty Two

In article . com,
wrote:

On Sep 25, 7:48 pm, Joe wrote:
On Sep 25, 8:53 pm, wrote:

I'm using a Hilti drill to drill holes into concrete ceilings.
Drilling overhead with a heavy drill and big bit is making it
difficult to keep the hole straight. The Hilti is more than up to the
job ... the problem is when you're applying upward force, the natural
tendency is to pull the drill toward you or away from you, which makes
for a slanted or "crooked" hole. Any tips on how to keep the drill
straight so as to achieve the straightest possible hole?

Do what mechanics have done for years: make a drill guide. Many ways
to do it, like use a drill press to drill a straight hole in a 2 x 4
for example. position it on the ceiling supported with a couple of
those screw jack thingies that cabinet installers use, or simply cut
the right length 2 x 4 to wedge under it. If you've got hundreds of
holes, have a machine shop make you a drill guide out of a steel plate
with the welded on guide piece sticking up out of the middle. Again,
support any way that works. Either way your job will go ten times
faster and dead true. HTH

Joe

This is way more along the lines of the kind of help I need. I'm an
electrical technician by trade, and this kind of work is a little out
of my field. I've never really worked with this kind of equipment and
processes before. Not much need for drilling holes into cement while
in the Navy! I'm working for a start-up company now and we're feeling
our way along this. Here's the rest of the story ... these holes are
being drilled into concrete ceilings that are normally about three
feet above a drop ceiling (ceiling tiles, etc.) and the concrete is
usually spotted with conduit, ducts, cabling, wiring, etc. So normally
we have very small spaces. I love the idea of a drill guide (kept
thinking there had to be something like that), but will have to find a
machine shop that can work with me on designing one for our specific
needs. Thanks a million for the post, great ideas for a fledgling
"driller."

A hole in a piece of steel makes a good occasional use drill guide. For
production use, a drill bushing is better. Those are available as stock
items, and are made from hardened tool steel. Take your mild steel
plate, bore a hole in it for the drill bushing, and press fit the
bushing into it. When you get the wobblies, the hardened drill bushing
will resist them better, for longer.

If you get to doing a lot more than three a week, there are a lot of
other tooling options; one would be to mount the drill to a jack affixed
to a mobile platform.