[mactec54]

I guess so. But i am not sure if it's enough to put the thermistor (temperature probe of thermostat) directly at spindle body. Would that be enough? I am affraid, that motor windings will reach temperature faster than the body of spindle. I am not sure how well it conducts the heat from windings to body.

That's is what I thought as well the winding will get to hot before the thermistor would turn on, if it was mounted externally, normally thermistors are mounted inside the motor, and are normally used to shut the motor down when it over heats

By correct positioning, thermistors can be located close to the thermally critical areas, or hot-spots, of the winding, where they closely track the copper temperature with a certain time lag, depending on the size of the thermistors and how well they are installed in the winding.

The Time lag may be to great in your case

The rated response temperature (RRT) of the thermistor is correctly selected for the class of insulation used on the winding. the thermistors are correctly located close to the thermally critical areas.
There is a low thermal resistance between the winding and the PTC thermistor. This depends on the electrical insulation between the winding and the thermistor. Since thermistors need to be isolated from high voltages, it is more difficult to achieve a low heat transfer resistance in HV motors, which have greater insulation thickness.

In these cases, to achieve complete protection, thermistors should be used in combination with electronic motor protection relays, which monitor the primary current drawn by the motor. this is where it gets even more complicated

So in reality it may not be as practical to use a thermistor, unless you are able to place and use them correctly

Did you try the Parameters setup I suggested