How to use a cartridge heater optimally ?

To ensure the best possible performance, it's important to get the fit right. Fit is the difference between the nominal diameter of the heating element and the maximum diameter of the hole. Cartridges must therefore be placed in holes calibrated with a reamer. The entire cartridge must be in contact with the metal (i.e. no lack of metal in the bore), with only the ceramic head protruding.