Which part of the flame should never come into contact with the base during brazing?

The inner cone of the flame should never come into contact with the base during brazing because it represents the hottest part of the flame. This region has a very high temperature and is used primarily for heating the metal being brazed. If the inner cone touches the base, it can lead to localized overheating, which may cause damage to the material or result in poor-quality brazing joints. Maintaining the right distance between the inner cone and the workpiece helps ensure that the heat is distributed evenly, allowing for proper melting of the filler material and effective bonding without risking overheating the base material itself.