Collet nut

From GAWDAwiki

A collet nut is a specific type of collet that is used to position and secure a contact/current tip within the welding torch or apparatus.

A collet nut usually exists in the form of a simple brass hex nut with a slotted extension that has the same inner-diameter as the nut. The extension is threaded, and when fastened, the extension constricts around the tip causing it to lock in place.^[1]

References

1. D/F Machine Specialties