How do I decide which size crimp to use for each beading wire size?
The way it works is that you need to have room for double the diameter of the wire to fit through the inside diameter of the crimp tube, plus room for the crimping to be done properly. The wall thickness varies on the crimps from manufacturer to manufacturer, which makes it hard to be exact on the amount of space which should be evident around the beading wire. The goal is to have enough room for the metal to surround the wire on all sides, so it is secure, yet not too much room that there is space for the beading wire to slip out. If the crimp is too small the metal will not surround the wire properly when crimped, allowing it to slip against the other length of wire passed through the crimp.