Rcbo neutral cables, cut to length

My crimpers form the ferrule into a square shape which might not be the best match for a round hole of a neutral bus bar. Are there better crimpers to use that would still keep the round shape once crimped? Perhaps once tightened into the terminal, the ferrule will have been deformed into a rounder shape anyway

Mine do the same - but one screwed down in the terminal they readily distort - very much so under the screw, maybe less so against the bar, but the remaining 'ribbing' perhaps improves contact and perhaps even pull-out resistance. I've noticed that some terminals these days are deliberately ribbed presumably to ever so slightly cut-into the conductor.

   - Andy.

My crimpers form the ferrule into a square shape which might not be the best match for a round hole of a neutral bus bar. Are there better crimpers to use that would still keep the round shape once crimped? Perhaps once tightened into the terminal, the ferrule will have been deformed into a rounder shape anyway

Mine do the same - but one screwed down in the terminal they readily distort - very much so under the screw, maybe less so against the bar, but the remaining 'ribbing' perhaps improves contact and perhaps even pull-out resistance. I've noticed that some terminals these days are deliberately ribbed presumably to ever so slightly cut-into the conductor.

   - Andy.

Yes mine leave a ribbed surface on the ferrule once crimped. I see that some crimpers form a hexagonal shape and some form a square shape. I presume that the square ones are more suited for the square clamp type terminals of mcb and rcd etc design and the hexagonal ones are more suited to the round neutral or earth bar type of terminal

Bear in mind that it doesn't need much contact area. If the two edges of the ferrule on the opposite side to the screw are squeezed against the curved tunnel wall such that the contact area of each edge is a thin strip about 0.5mm x 6mm, then that gives a total contact area of 6mm², big enough for most N leads. This glosses over nickel vs copper conductivity, not perfect contact etc.; but gives a rough indication that even if the ferrule isn't fully crushed into a curved shape, it's likely to be ok.