1、drilling The bi-metal screws can penetrate into copper plates in 0-12mm directly by using tapping machine and the length of the alloy steeldrilling head also can be designed as different requirment. 2、Tapping The tapping thread lines in the alloy steel will be more easy to fit the new phatnoma while penetrating into the iron or aluminum board inside after locate special heat treatment. 3、locking A2 or A4 stainless steel series strenthen the thread lines by a cold forging treatment during whole process; maintain special corrosion?resistant without any heat treatment; screwing in alveolar into fasteners smoothly then finish the fastening combination to achieve excellent efficacy in resistance to pull out and weatherproof by the way that don’t destroy the thread lines steadily andtightly.