Self-tapping Screws are of two types.
* Thread forming – these are ideal for plastic devices and equipments. They hold the material tightly but there is a risk of damage if they are tightened or brass thread inserts beyond the limit.
* Thread cutting – these are best for wood and metal devices wherein they completely remove that portion of the material while drilled and create a clean path for the screw. Care must be exercised while disassembling the device.