I have a 60A switch, but am installing a gas freestanding stove that only needs power for the ignitor sparks. The wire gauge coming out of the wall from the switch is 4mm or 6mm. The wires coming from the stove are normal plug type thickness. About 2mm. Can I just connect the thicker wire to the thinner? Even though its 60A.

You say you have a 60 amp switch. Is that your circuit breaker?

If the stove is new, the manual will tell you what size breaker you need to operate it.

It is not safe or legal to connect a 60 amp breaker to a wire that is not rated for 60 amps.

Run the correct size wire with the correct size breaker.

Chuck

Yes, closely follow the manufacturer's installation instructions... in the US it's required.

The wire is 4mm to 6mm? That is either 8 or 6. The ignitors probably use less than 5 amps but you would use a 15 amp CB. You need to look at the electrical requirement for the gas stove you are installing and wire according to the specifications... That 60 amp line is way too heavy.