Types of dangerous sparks inside drilling machine that require to stop work immediately

Question

This question mention that it is common to see sparks inside a drilling machine.

It is not uncommon to see sparks at the interface point between the carbon brush and the commutator as the motor operates.

So, is there a particular kind of spark inside the drilling machine that is dangerous and requires stopping work immediately and getting it fix? and also, do old drilling machine have fewer sparks than new drilling machines (the question mentions that old drilling machines produce more sparks, while the answer mentions that new drilling machines produce more sparks, both statement are contradictory to each other)?

I went through a few forum threads where people said sparks inside brushed drill machines are common, but all of them mentioned old drill machines

The amount of sparking will often reduce as the brushes wear in during use of the tool.

Answer 1

You know the ordinary low level sparks which dance across the commutator? And you know the ordinary sparks from metalworking? Any sparks other than those are dangerous and a sign it's time to stop using the machine.

The amount of sparks has everything to do with the health of that particular set of brushes and commutator, and little to do with the make, age, class, etc. of the machine.

Answer 2

If you look through the vent holes in the body of the drill, you should see small sparks between the carbon brushes and the commutator. These often diminish with time and wear-in, since the better the brushes fit, the less spark gap is present.

Any other sparking (from the cord, along the body) is a severe safety hazard and presents a life-threatening risk. The most common fault would be a frayed or weakened power cord at the point it joins the body of the drill. If anything other than the brushes is sparking, immediately take the drill out of service, and tag it so nobody else uses it until it's repaired.