"I used these to fix a wood batten to a steel beam above a window bay. The steel was a lot thicker than 5mm so I used a 5mm diameter HSS bit to drill a pilot hole. The thread on these screws bit in to the pilot hole in the steel with ease and the batten is well fixed."
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Review 2 for Timco Classic C-1022 Steel Self-Drilling Roofing Screws 5.5 x 70mm 100 Pack
"Typical Trimco quality, due to the lengh of the screw , start slowly until the drill bit part bites, then away you go. A word of caution. with impact drivers it is easy to strip the thread, so do not over tighten."