Did you drill out the existing insert M6 thread with an 8mm Drill then install the self-threading mcmaster insert into the existing? Or do these completely replace the existing?MCMASTER CARR
McMaster-Carr
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.www.mcmaster.com
We used these in past worked great https://www.mcmaster.com/inserts/tapping-inserts-for-plastic/