ryan_vd
This is a subject which tends to result in a religious debate which runs on and on.
But in a nutshell, a CHT gauge is used to check that the engine is not getting too hot. This can occur during the following
In climb (high power but airflow around the engine too low),
During deliberate slow flight (high power because one is on the back of the power curve, but again airflow too low)
Engine mismanaged (detonation or even pre-ignition)
If the cylinder head gets too hot, the metal (aluminium usually) gets weak and will crack. Most likely, other bits will also be too hot.
One can also use a CHT gauge to lean the engine correctly but an EGT gauge is much more accurate and responsive for doing that. Especially if it is a multi-cylinder display e.g. EDM700. You can look at
www.jpinstruments.com for some reading.