collet
nounUK /ˈkɒlɪt/
US /ˈkɑːlɪt/
A small ring or collar that holds a tool or part tightly in place.
The jeweler tightened the collet to hold the gemstone securely.
OTHER MEANINGS
2. A small band or ring worn around the finger.
She wore a simple gold collet on her little finger.
3. The part of a ring that holds the stone.
The collet was bent, so the diamond wobbled.
4. A cone-shaped piece in a watch that holds a pivot.
The watchmaker replaced the worn collet in the movement.