If a necklace is breaking at the crimp area, then the crimps may need to be crimped more securely. To add security to your crimp, we suggest using a bit of Loctite® 454 Gel adhesive next to the crimp. You'll get the best crimping results when you use crimping pliers on crimping beads. You can review the ''How To Crimp a Crimp Bead/Crimp Tube'' how-to video and illustrated instructions to confirm that the technique is correct.
For increased durability and longevity around clasp components, consider adding Accu-Guard™ wire protectors to the design. Accu-Guard wire protectors are designed to protect wire against wear from clasps and other sharp-edged components. Similar to bullion or French wire with a rigid, pre-curved horseshoe shape to cradle and protect your bead stringing material from fraying.
If you find that crimping isn't giving you the look you want, experiment with Screw-Tite Crimps™. They're a convenient and re-useable alternative to traditional crimp beads.