When a person is cremated why are there no chunks of gold in the ashes does the undertaker take the teeth out or does the gold vaporize?

Gold does not vaporize.

Once a body is cremated, the remains are put into a machine called a Cremulator. This grinds the leftover bone into a fine ash.

Items not destroyed through the cremation process (artificial hips, gold teeth) are then extracted.

Some crematoria recycle precious metals and donate the proceeds to charity. Others keep the profits.