Flutes

Threads

Diameter

Relief

Larger than the tap size

Smaller than the tap size

Equal to the tap size

Equal to the core (minor) diameter of the tap

On irregular jobs

To reduce the metal rapidly

On wood

If smooth file is not available

Insufficient cooling effect

Danger of corrosion

Decrease in cutting action of drill

Quick evaporation of water

External thread cutting tool

Internal thread cutting tool

Square thread cutting tool

Acme thread cutting tool