Open end thermocouples should be sealed with a moisture sealant such as “Thermoseal” after conductors have been exposed prior to attaching leadwire. A small, easily assembled transition fitting for adapting sheathed, mineral oxide insulated thermocouples to leadwires. the leadwire adapter completely encapsulates the transition splice forming an insulating shield and providing an effective strain relief. The adapter provides for secure mounting on the sheathed thermocouple and a spring allows the