Since 1914, self tapping screws started commercialization. the first set of self-tapping screws
Self tapping screws
Of-mainly from wood screws-carburizing steel tapered tail belongs to a thread forming screws. Main purpose at that time was used in the air conditioning system duct metal joining, also known as metal screws. After more than 80 years of development, can be divided into four stages-a total thread forming, thread cutting, thread rolling and drilling.