Ground surfaces provide accurate positioning inside of t-slot. These nuts are manufactured from S45C(JIS) / CK45(DIN) heat treated to HRC 30-35 and have a black oxide surface finish.
Gripper jaws can be a great way of getting round part movement in roughing operations, this is by use of teeth in the jaw which bite into the material. This biting can also be a great way to get round problems using black bar or other rough material....