Lockwood locks ha e been around d for a lo g time that you think they would have got their design and screw quality right by now. I screw it to 2.5mm steel and the self threading screws are rubbish. I had the backing g plate mounted to dead flat 3mm steel plate and I had to shim the mounting plate out to het the lock to locate. You need to better Lockwood. The lockshop however was terrific to deal with .