The nut which has a cylindrical grooved collar at its lower end and this collar fits into a corresponding recess in the adjoining piece is named as.

Correct Answer: Grooved nut
Grooved nut is a nut which has a cylindrical grooved collar at its lower end and this collar fits into a corresponding recess in the adjoining piece. A set-screw is inserted through the nearest face of the piece. The dog-end of the set-screw enters the groove and prevents slackening of the nut.