Maybe an easier approach would be cutting away the broken off screws, Ernst.

There are some small hole saws for use in drills or die grinders with 1/4"
collets that could be used to cut out the base metal around the frozen
screw.
I saw some yesterday that had diamond grit on them, but carbon steel saw
teeth or carbide grit would likely be better.

Another method would be to use a piece of tubing in a drill chuck and dip it
in a grit paste like valve grinding compound. May get a bit messy, but a
good solvent on a rag should be all that's required for cleanup, just avoid
too much rubbing.

I think you mentioned the screws were in a window frame of some sort. If
there is a feature (channel or edge) that would position a guide over the
screw stub (so the hole saw can't run away), make up a guide for a small
hole saw that could be clamped into position for cutting out a broken screw,
then repositioned over another, etc.

It shouldn't be too difficult to find something to fill the hole (push-in
plastic gizzy, etc) for a new screw to anchor in.. or just fill the holes
with some "miracle hole filler in a tube" and screw into that.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Ernst" wrote in message
...
Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst