I will often modify the shape of my silicone mandrels with a file (it’s an old and also cheap file I obtained at a hardware store). In this instance I wanted the mandrel flat so I could work inside my ring but you can create all types of curves. The mandrel i’m using is an AdvantEdge Silicone Polisher in white (coarse). These mandrels are amazing for polishing the inside of rings, I bought mine @riogrande #metalsmithsociety #jewelerstools #jewelrymakingprocess #benchjeweler #riojeweler #jewelrypolishing #polishing