Triangular-headed screwdriver

[Philip Davies]

I just have to undo some small screws, with an equilateral triangular recess, from a piece of electronic equipment, so I can get at the transformer inside.
Although it’s usually possible to undo these with a flathead or slot screwdriver, these were in a bit tight. So I took a spare 3-square tapered file, and just ground a slight flat on each face of the tip. The handle is also spare, turned from cherry. I did not temper the file.
Is anybody going to tell me that I mustn’t do that sort of thing?