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Carbon steel drills are cheap but don't last long between sharpenings.
Suggest high speed steel drill bits as a minimum material.
As descreibed, "coated" drill bits are only coated with a thin film; most effective for advertising (cobalt, ti, etc.).
Suggest learn how to sharpen a drill bit. It's not difficult, but there's a right way to do it.
Yes, Drill feed and speed are important factors.
I often use step drills. It's easier to drill a large hole by gradually enlarging the hole via the steps, especially in thin sheet metal.
Sherwood
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