However one the clip screws broke off inside the threads and I still haven't managed to get it out if anyone has any ideas...
what are the clip screws on that knife threaded into?
if they're threaded into aluminum scales, you should be able to use some plasticine modeling clay to make a dam around the broken screw and then put a few drops of Nitric Acid on it. you're probably going to want some modeling clay stuffed in the back side, or completely disassemble the knife so the acid doesn't leak thru and eat any other parts.
IIRC, Nitric will eat carbon or stainless steel, but won't eat aluminum. i've seen it used to remove broken taps from aluminum parts.
don't know what it would do to CF or G10 scales, or titanium.
in a short search the smallest Left HAnded Drill Bit i can find is 1/16" which will be too big for these screws, but if you can find a smaller one, AND the knife has flat scales you could chuck the LH bit in a press and carefully tru to drill the broken screw out with light pressure. sometimes the bit will grab the screw and back ip out.
a NUMBERED mit set has buts in smaller increments than a normal index, and i've drilled out M5 bolts using a numbered set and a hand drill. but that's MUCH largerthan pocket clip screws.
a Dremel, with a set of small, pointy diamond bits might work, but it's going to take a lot of slow, careful grindage.
if you take apart the whole knife, you can use regular drill bits to drill the broken screw out from the back side, and it may unscrew the broken screw and push it out.
if you have Loctite on the threads, you may need to use a soldering iron or a heat gun on the broken stub to soften it (the adhesive, not the screw)
on larger bolts it's possible to TIG a nut onto the broken stub and the heat shock often loosens up the threads and makes it easy to back it out.
on larger bolts it's also possible to try and turn it with a sharp punch. not likely to work if it's tight, and then there's screw extractors which sometimes work, and sometimes they break and really fuck things up.