I have found, when enlarging prepunched holes (typ. #40) to sizes like #19 for nutplates, it’s very difficult to not end up mangling the hole.
I’ve tried backing it up with wood.
Pressing hard and soft
Air drill and electric (fast and slow)
Starting from #40, and opening it up as close to #19 as I can with a unibit.
These are brand new, colbalt jobber bits from Cleveland.
The bit always seems to bite really hard and then get stuck. This invariably mangles the material a bit. To salvage I usually have to reverse the drill, to get rid of the attached curls, then spin forward again.
On a drill press, sometimes it’s fine, but if it’s a smaller piece, I’ve had the bit get stuck and spin the whole piece.
So far I’ve been lucky and not cracked a skin, and if the hole was a little larger, it’s still just for a nut plate, so no huge deal ... but I’d like to know how to do it right as I’m sure there are a lot more of these.
Thanks!
I’ve tried backing it up with wood.
Pressing hard and soft
Air drill and electric (fast and slow)
Starting from #40, and opening it up as close to #19 as I can with a unibit.
These are brand new, colbalt jobber bits from Cleveland.
The bit always seems to bite really hard and then get stuck. This invariably mangles the material a bit. To salvage I usually have to reverse the drill, to get rid of the attached curls, then spin forward again.
On a drill press, sometimes it’s fine, but if it’s a smaller piece, I’ve had the bit get stuck and spin the whole piece.
So far I’ve been lucky and not cracked a skin, and if the hole was a little larger, it’s still just for a nut plate, so no huge deal ... but I’d like to know how to do it right as I’m sure there are a lot more of these.
Thanks!