Most unsuitable method for removal of a tap that was broken inside an aluminium job? 

Explanation:

Methods of removing broken taps:
Use of tap extractor:

• This is a very delicate tool and needs very careful handling.
• This extractor has fingers that can be inserted into the flutes of the broken tap.
• The sliding collar is then brought to the surface of the work and the extractor is turned anticlockwise to take out the broken tap.
• A light blow on the broken tap with a punch will help to relieve the tap if it is jammed inside the hole.

Annealing and drilling the tap:

• This is a method adopted when other methods fail.
• In this process the broken tap is heated by flame or by other methods for annealing.
• A hole is then drilled into the annealed tap.
• The remaining piece can be removed either by using a drift or using an Ezy-Out (extractor).
• Most unsuitable method for the removal of a tap that was broken inside an aluminum job is the annealing and drilling method.
• This method is not suitable for workpieces with low melting temperatures such as aluminum, copper, etc.

Use of arc welding:

• This is a suitable method when a small tap is broken at the bottom of materials like copper, aluminum, etc.
• In this method the electrode is brought in contact with the broken tap and stuck so that it is attached to the broken tap.
• The tap may be removed by rotating the electrode.