Bearer wire

Before I realised (thank you , kind members of this forum :) ) that I could solder on a jump ring or wire, I bought a bit of bearer wire to try out. I've cut it very carefully, using a mitre cutting jig and set square, checking that all angles were 90 degrees, that there were no burrs, that both ends were identical, but every time, and I mean every, every time, and they have been many, there is a tiny (less than hair-width) sliver of light at the join, between the two ends, at the upper, thinner part of the wire. Nothing cures it and it is reducing me to screams of frustration. Soon I'll have filed it all away to dust. Any suggestions would be most gratefully received.

The heat is most likely causing distortion, does the bezel sit relaxed or does it hold together under tension try using a physical restraint of some kind to to keep the joint tight e.g. clamps, bailing wire and be vary sparing with your flame especially at the thin section. Flame control is a large part of the soldering process comes with practice.

I guess this is happening before soldering, when you are trying to get the edges to match?

I have to admit it is a very frustrating material to work with, but as you are determined to have a go, stand it upside down on your bench peg, which is best flat side up, not sloping.
Hold it together with finger and thumb, and gradually saw the blade (about a 4/0) obliquely down the join. It's easy to go astray.

Once cut, manoeuvrer the edges together as perfectly as possible. Ring pliers with one beak flat and one beak curved(for inside) are
Useful for this. Dennis'

Thank you both for the replies. Yes, this is before soldering. The thick part joins perfectly, but there is invariably a minuscule flash of light in the upper, thinner part. I wouldn't try to solder with a gap. I do have ring pliers. I've tried cutting through the join but as the material is a bit flimsy the ends tend to move apart as I cut. Perhaps I should give up, send the bit I bought back for scrap and use jump rings and wire in future.

Sorry misinterpreted the question.