Metric Robotics Nuts
On this page are examples of Expansion-Type Fasteners which have been developed to solve specific fastening problems. The expansion principle is the same, but forms vary to: plug a temporarily unused hole, provide vibration-resisting adjustment, fasten in wood, heavy gauge metal or odd-shaped panel holes. They illustrate Tinnerman's ability to help the manufacturer fasten his product better, faster and at a lower cost.
Perhaps one of these Specials will suit or suggest an answer to your particular fastening problems.