A cast iron rod is placed through holes at the end of a 'U' shaped bracket. Running down the center of the bracket is a steel rod with wing nut on one end and a hole for the cast iron rod at the other. As heat is applied to the steel rod by means of a Meeker burner the steel rod expands, allowing the wing nut to be tightened every 30 seconds or so. After about 5 minutes the flame is removed and the steel rod allowed to cool. As the steel rod cools it shrinks, pulling against the cast iron rod until it breaks.