One of the things that I'm currently interested in undertaking is building an army for primarily 30k, rather than 40k. But I'm also keenly aware of the cost of such an undertaking. Hence one of the ways in which I want to try to save a little bit of money is to search my bits box for potentially useful parts that can double up, or be appropriated for 30k parts.
One obvious source of bits for me is the humble chaos space marine sprues. As I've been an avid chaos space marine collector over the years, I find that I have plenty of bits from that range (both present and past moulds).
Pictured above is one of the shoulder pads available on the chaos space marine sprue. But for 30k, I'm really not interested in the chaos star and skull that is depicted on the left hand side. Instead, I'm simply interested in a "blank" version of this, with the pseudo-heresy era protective strip (or even: earlier mark power armour) added around the edge.
To achieve this, I went back to the trusty combination of the modelling knife and file. Using the knife, I carefully started to slice off the skull and the arrows on the curvature of the pad. Once these were reasonably flat and removed from the pad, I then proceeded to apply a careful filing of the pad. As can be seen, this is imprecise, as getting the exact curvature of the original sculpt is highly tricky with simply a file. That said, it is reasonably smooth and I think it will suffice perfectly for a 30k pad - especially when it gets painted up with a bit of battle damage / chipped paint coupled with a defaced legion symbol.