We have three products for thread strengthening or repair in both Imperial and Metric:-
These are solid bushes that are inserted in to a threaded hole. They have small, sharp keys that can be driven in to the material making a permanent key so the bush never turns. The outside thread is a UNC for Imperial or Metric fine for Metric. These derive from the aircraft industry and are the best of the three systems we have in terms of cost and quality. No special tooling is required.
These are similar to above and have a thinner wall. They require a special tooling kit.
A thin coil of stainless steel wire which can be wound in and require a special tooling kit.