Femurat, if you drilled the hole up the end of the key first, the best way to file the outer diameter round is to utilise the hole you’ve drilled- because the outside diameter you’re filing needs to be concentric with that hole.
clamp a stub of round bar or wire (or even the drill itself) the size of the drilled hole, protruding from the bench vice, then slip the key over it and slowly pivot it back and fore while filing it with smooth forward strokes.
Its the best method to get it accurately round by hand.
That way you are turning the key perfectly concentric to the action of your file.
Since the key is square being gradually filed to a round shape, guiding it by the outside means its eccentrically ‘bumping around’ in the notch, and not even to the action of the file.
Hope this makes sense, it’s a technique which not only makes it easier To do but eliminates the ‘bumping’ effect and makes it accurate, although it does look like it’s coming along nicely anyway, and don’t forget keep us posted on the box as well 🙂
