My DMM probes have a 6-32 male thread that allows the plastic barrel to be unscrewed to replace the test leads when they eventually wear out. I machined some copper slugs the same diameter as the inside diameter of the soldering ends of the alligator clips, drilled and tapped a 6-32 nut-thread through the slug, then soldered the slug to the alligator clip. It takes a LOT of heat and appropriate flux to get a good solder joint!
To use the alligator clip with the DMM leads, I just screw the copper slug onto the end of the probe. Also, I apply some red and black heat-shrink tubing over the end of the alligator clip (avoiding the jaws) to help identify the probe polarity, although the barrel of the test probe and the color of its wire do the same thing. I just thought the shrink tubing looked neat.
