This wire splicer jig is a simple assembly to make and is easy and fast for joining wires together.
Download the stl file. It has been repaired in Netfab.
I printed it at 60mm/sec with PLA.
The pictures show how wire is attached with alligator clips. These are small ones that I got at Radio Shack.
Note that I hot melted a lead weight inside so it would stay solid on the bench.
I was using a washer in a vise that I learned from someone, but it was hard for me to get the wire aligned.
Keep the soldering iron away from the plastic.