I was going to suggest running a tap through the large hole and using a couple of grub screws, from front and back, then I saw this.
The little grub screw from the side is an absolutely awful and rather sketchy way to clamp a brake cable.
@Kimmo started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.