How to drill this conical hole on M.S. & S.S. plate? We have three steps, we choose three specification drilling bits to drill the plate, which maximum can be 20mm thickness. For example, when we drill one plate with 20mm thickness, first we use middle size drilling bit to drill the depth of 18mm, then use small drilling bit to drill the last 2mm plate, finally use big size drilling bit to make the top hole bigger until the depth of 10mm. Of course the plate thickness is based on customers’ requirement, we take use of the imported drilling bit, which can be seen in china market rarely, that’s the reason why we can make the conical hole for our customers.