Martin Brown wrote:
On 26/05/2017 11:48, Dan S. MacAbre wrote:
DICEGEORGE wrote:
glue/screw/nail an offcut to the outside / other side of the door.
drill new hole into that and through the door.
remove offcut

[g]

It might work if the offcut is at least as thick and strong as the door
being cut into, but the breakthrough into the asymmetric cut is likely
to be traumatic and difficult to control throwing the drill hard.

I was thinking of that after I posted. I'm not sure that the flat bits
I have will continue to go straight once they're in the hole, although
they do have flat sides, which I suppose will help, and then I just have
to hold it straight.

It is getting difficult to work out what you are trying to do. I
imagined a hole *through* a door for a handle but elsewhere it sounds
like you are talking about a blind hole into the door frame.


I am trying enlarge the blind hole that receives the mortice latch in
the side of an interior door. The old one has a tubular barrel about
22mm in diameter. I want one with a longer backset, to move the knob
away from the frame (so yes, I will need to make some other holes
through the door, but that seems easy enough), but the longer latches
all seem to be 'heavy-duty' and require holes about 24/25mm in diameter.

I do regret not being clear enough, but I do now have plenty of
suggestions :-)

If there is a hole right the way through you could trace out the shape
and use a fret saw to cut the extra part out.

There are hybrid chunky drills that are midway between a twist drill and
a milling tool or a cone step drill which might just work if it is long
enough to be centred on scrap offcut nailed to the far side. Even so you
are going to get a kick off it every time the cutting side bites.

It does sound like the first thing I should try,
just to see how it goes. The wood (oak) is hard, which I think will
help to control things a bit.

Unfortunately it will make it incredibly difficult to control once you
have a cut into hard material on one side and no resistance at all on
the other probably flicking the drill out of your hands.

This is one example where the right hand tool will beat power tools.