spine/cheek trimming question

[engle's-wilder]

I have been wondering, if you wanted to make a thick knife thinner (trimming the spine or the sides) or a thick axe thinner (trimming the cheek), would it compromise the integrity of the blade of either? I know that steels aren't always as hard towards the middle of a piece so how far can I file and trim down a knife or a hatchet and not have to worry about it's integrity? (let's say the knife is a BK2 and the hatchet is just more wedge-shaped than I'd like for bushcraft)

thanks!